US20190345588A1

US20190345588A1 - Methods to increase titanium in aluminum alloys

Info

Publication number: US20190345588A1
Application number: US15/975,159
Authority: US
Inventors: Michael J. Walker; Qigui Wang; Andrew C. Bobel; James R. Salvador; Henry Zhan
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2018-05-09
Filing date: 2018-05-09
Publication date: 2019-11-14
Also published as: CN110468307A; DE102019110793A1

Abstract

A method of making an aluminum alloy containing titanium includes heating a first composition to a first temperature. The first composition includes aluminum. The first temperature is greater than or equal to a liquidus temperature of the first composition. The method further includes adding a second composition to the first composition to form a third composition. The second composition includes a copper-titanium compound. The method further includes decomposing at least a portion of the copper-titanium compound into copper and titanium. The method further includes cooling the third composition to a second temperature to form a first solid material. The second temperature is less than or equal to a solidus temperature of the third composition. The method further includes heat treating the first solid material to form the aluminum alloy containing titanium.

Description

GOVERNMENT SUPPORT

This invention was made with government support under DE-AR0006082 awarded by the Department of Energy. The Government has certain rights in the invention.

INTRODUCTION

This section provides background information related to the present disclosure which is not necessarily prior art.
The present disclosure pertains to methods for increasing titanium in aluminum alloys by the introduction and dissolution of copper-titanium compounds, alloys, and powders.
As background, components formed using aluminum alloys have become ever more prevalent in various industries and applications, including general manufacturing, construction equipment, automotive or other transportation industries, home or industrial structures, aerospace, and the like. For example, aluminum alloys are commonly used in manufacturing industries for castings, such as, for example, engine heads, engine blocks, transmission cases, and suspension components in the automobile industry. It is often desirable to increase thermal stability of aluminum alloys for elevated temperature applications by increasing solid state titanium levels to improve microstructure and avoid degradation of mechanical properties of the alloy. However, titanium generally has low solubility in various aluminum alloys, thus posing challenges with enhancing an amount of solid state titanium in aluminum alloys.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
In various aspects, the present disclosure provides a method of making an aluminum alloy containing titanium. The method includes heating a first composition to a first temperature. The first composition includes aluminum. The first temperature is greater than or equal to a liquidus temperature of the first composition. The method further includes adding a second composition to the first composition to form a third composition. The second composition includes a copper-titanium compound. The method further includes decomposing at least a portion of the copper-titanium compound into copper and titanium. The method further includes cooling the third composition to a second temperature to form a first solid material. The second temperature is less than or equal to a solidus temperature of the third composition. The method further includes heat treating the first solid material to form the aluminum alloy containing titanium.
In one aspect, the heat treating the first solid material facilitates a formation of a plurality of aluminum-titanium precipitates. The aluminum-titanium precipitates are a distinct phase in the aluminum alloy containing titanium.
In one aspect, the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates have an average diameter of less than or equal to about 500 microns (μm).
In one aspect, the aluminum alloy containing titanium includes a matrix including aluminum. The matrix has titanium dissolved therein. A combined amount of titanium in the plurality of aluminum-titanium precipitates and the matrix is greater than or equal to about 0.1% by mass to less than or equal to about 1.39% by mass of the aluminum alloy containing titanium.
In one aspect, at least a portion of the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates includes Al₃Ti.
In one aspect, the heat treating the first solid material facilitates a formation of a plurality of aluminum-copper precipitates. The aluminum-copper precipitates are a distinct phase in the aluminum alloy containing titanium.
In one aspect, the decomposing at least a portion of the second composition and the cooling the third composition are performed concurrently.
In one aspect, the copper-titanium compound is selected from the group consisting of: Ti₃Cu, Ti₂Cu, TiCu, Ti₃Cu₄, Ti₂Cu₃, TiCu₂, TiCu₄, Ti_xCu_1-x, CuTi_yZr_2-y, and combinations thereof.
In one aspect, the heat treating the first solid material includes heating the first solid material to a third temperature to form a second solid material. The third temperature is less than the solidus temperature of the third composition. The heat treating further includes cooling the second solid material to a fourth temperature to form a quenched second solid material. The fourth temperature is less than the third temperature. The heat treating further includes heating the quenched second solid material to a fifth temperature to form a third solid material. The fifth temperature is greater than the fourth temperature and less than the third temperature. The heat treating further includes cooling the third solid material to a sixth temperature to form a quenched third solid material. The sixth temperature is less than the fifth temperature. The heat treating further includes heating the quenched third solid material to a seventh temperature to form the aluminum alloy containing titanium. The seventh temperature is greater than the sixth temperature and less than the fifth temperature.
In one aspect, the fifth temperature is greater than or equal to about 350° C. to less than or equal to about 450° C. The seventh temperature is greater than or equal to about 150° C. to less than or equal to about 250° C.
In one aspect, the cooling the third composition to the second temperature is performed at a first cooling rate. The first cooling rate is greater than or equal to about 0.1° C./second to less than or equal to about 100° C./second. The cooling the second solid material to the fourth temperature is performed at a second cooling rate. The second cooling rate is greater than or equal to about 0.5° C./second to less than or equal to about 150° C./second. The fourth temperature is greater than or equal to about 20° C. to less than or equal to about 300° C. The cooling the third solid material to the sixth temperature is performed at a third cooling rate. The third cooling rate is greater than or equal to about 0.5° C./second to less than or equal to about 150° C./second. The sixth temperature is greater than or equal to about 20° C. to less than or equal to about 200° C.
In one aspect, the heat treating the first solid material includes heating the first solid material to a third temperature to form a second solid material. The third temperature is less than the solidus temperature of the third composition. The heat treating further includes cooling the second solid material to a fourth temperature to form a quenched second solid material. The fourth temperature is less than the third temperature. The heat treating further includes heating the quenched second solid material to a fifth temperature to form a third solid material. The fifth temperature is greater than the fourth temperature and less than the third temperature. The heat treating further includes heating the third solid material to a sixth temperature to form a fourth solid material. The sixth temperature is greater than the fifth temperature and less than the third temperature. The heat treating further includes cooling the fourth solid material to a seventh temperature to form a quenched fourth solid material. The seventh temperature is less than the sixth temperature. The heat treating further includes heating the quenched fourth solid material to an eighth temperature to form the aluminum alloy containing titanium. The eighth temperature is greater than the seventh temperature and less than or equal to the fifth temperature.
In one aspect, the fifth temperature is greater than or equal to about 250° C. to less than or equal to about 400° C. The sixth temperature is greater than or equal to about 350° C. to less than or equal to about 500° C. The eighth temperature is greater than or equal to about 150° C. to less than or equal to about 250° C.
In one aspect, the cooling the third composition to the second temperature is performed at a first cooling rate. The first cooling rate is greater than or equal to about 0.1° C./second to less than or equal to about 100° C./second. The cooling the second solid material to the fourth temperature is performed at a second cooling rate. The second cooling rate is greater than or equal to about 0.5° C./second to less than or equal to about 150° C./second. The fourth temperature is greater than or equal to about 20° C. to less than or equal to about 300° C. The cooling the fourth solid material to the seventh temperature is performed at a third cooling rate. The third cooling rate is greater than or equal to about 10° C./second to less than or equal to about 100° C./second. The seventh temperature is greater than or equal to about 20° C. to less than or equal to about 300° C.
In one aspect, the aluminum alloy containing titanium includes titanium at greater than or equal to about 0.1% by mass to less than or equal to about 7.5% by mass.
In one aspect, the first composition further includes at least one of silicon and magnesium.
In one aspect, the second composition is in the form of a plurality of particles. The plurality of particles is at least partially encased in a fourth composition. The fourth composition includes aluminum.
In one aspect, the aluminum alloy containing titanium includes an average grain size of greater than or equal to about 10 microns (μm) to less than or equal to about 10 centimeters (cm).
In other aspects, the present disclosure provides an aluminum alloy comprising titanium. The aluminum alloy comprising titanium includes a matrix, a plurality of aluminum-titanium precipitates, and a plurality of aluminum-copper precipitates. The matrix includes aluminum. The aluminum alloy comprising titanium includes titanium at greater than or equal to about 0.15% by mass to less than or equal to about 2% by mass. The aluminum alloy comprising titanium includes copper at greater than or equal to about 0.05% by mass to less than or equal to about 10% by mass.
In one aspect, at least a portion of the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates include Al₃Ti. The aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates have an average diameter of less than or equal to about 50 microns (μm). The aluminum-copper precipitates of the plurality of aluminum-copper precipitates have an average diameter of less than or equal to about 5 microns (μm).
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is an exemplary partial phase diagram of a binary aluminum-titanium system showing a peritectic transition at about 665.4° C.;

FIG. 2 is an exemplary partial phase diagram of a binary aluminum-copper system;

FIG. 3 is an exemplary partial phase diagram of a binary copper-titanium system;

FIG. 4 is an exemplary isopleth diagram of a 7% silicon-0.75% copper-aluminum-titanium system according to certain aspects of the present disclosure;

FIG. 5 is a flowchart depicting a method of making an aluminum alloy containing titanium according to certain aspects of the present disclosure;

FIGS. 6-9 are dissolution estimates of a 5 μm Ti₂Cu particle in aluminum;

FIG. 6 shows dissolution of titanium in liquid aluminum;

FIG. 7 shows dissolution of copper in liquid aluminum;

FIG. 8 shows dissolution of titanium in solid aluminum;

FIG. 9 shows dissolution of copper in solid aluminum;

FIGS. 10-11 are schematic diagrams of heat treatments according to certain aspects of the present disclosure;

FIG. 10 represents an exemplary five-step heat treatment;

FIG. 11 represents an exemplary six-step heat treatment; and

FIG. 12 shows a correlation between particle radius and mean particle spacing for different titanium concentrations.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, elements, compositions, steps, integers, operations, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Although the open-ended term “comprising,” is to be understood as a non-restrictive term used to describe and claim various embodiments set forth herein, in certain aspects, the term may alternatively be understood to instead be a more limiting and restrictive term, such as “consisting of” or “consisting essentially of.” Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and/or process steps, the present disclosure also specifically includes embodiments consisting of, or consisting essentially of, such recited compositions, materials, components, elements, features, integers, operations, and/or process steps. In the case of “consisting of,” the alternative embodiment excludes any additional compositions, materials, components, elements, features, integers, operations, and/or process steps, while in the case of “consisting essentially of,” any additional compositions, materials, components, elements, features, integers, operations, and/or process steps that materially affect the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, features, integers, operations, and/or process steps that do not materially affect the basic and novel characteristics can be included in the embodiment.
Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed, unless otherwise indicated.
When a component, element, or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other component, element, or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms, unless otherwise indicated. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially or temporally relative terms, such as “before,” “after,” “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially or temporally relative terms may be intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures.
Throughout this disclosure, the numerical values represent approximate measures or limits to ranges to encompass minor deviations from the given values and embodiments having about the value mentioned as well as those having exactly the value mentioned. Other than in the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, “about” may comprise a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%.
In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range, including endpoints and sub-ranges given for the ranges.
Example embodiments will now be described more fully with reference to the accompanying drawings.
As generally discussed above, aluminum alloys are widely used in vehicles, such as automobiles, motorcycles, boats, tractors, buses, mobile homes, campers, and tanks. The use of aluminum alloys will continue with efforts to reduce vehicle mass and save space. Methods of processing aluminum alloys according to the present technology form components with reduced mass relative to components made with traditional alloys, such as steel, while maintaining strength and ductility requirements. Aluminum alloys are particularly suitable for use in components of an automobile or other vehicles (e.g., motorcycles, boats), but may also be used in a variety of other industries and applications, including aerospace components, industrial equipment and machinery, farm equipment, and heavy machinery, by way of example.
Aluminum and its alloys are lightweight and are therefore desirable for use in fuel-efficient vehicles. One factor that may limit automotive applications of aluminum and its alloys is its thermal stability, which may result in decreased performance at temperatures above about 200° C. The use of titanium in an aluminum alloy has the potential to alter the microstructure to improve mechanical properties of the alloy. Thus, there is a need for methods of making titanium-containing aluminum alloys and methods of increasing the amount of titanium in aluminum alloys. The addition of titanium in aluminum alloys according to certain aspects of the disclosure may improve both high temperature and room temperature mechanical properties of the aluminum alloy.
Creating aluminum alloys having titanium may present certain challenges. In particular, titanium can be difficult to dissolve in aluminum. A typical method of making an aluminum alloy may include preparing an aluminum melt and adding a master alloy including an aluminum-titanium compound. The master alloy is commonly Al₃Ti in an aluminum matrix. Titanium does not readily dissolve in the aluminum in large quantities because (1) liquid aluminum has a low solubility for titanium, (2) Al₃Ti is stable in the aluminum melt, and (3) Al₃Ti has a high density compared to the aluminum melt. More particularly, because the liquid solubility of titanium in aluminum is so low, as discussed in greater detail below, most of the titanium remains as a secondary Al₃Ti phase rather than being incorporated into the alloy.
More particularly, only a small amount of the Al₃Ti decomposes so that the titanium can dissolve in the liquid aluminum. The remaining Al₃Ti sinks to the bottom of the aluminum melt because the density of Al₃Ti is high compared to that of the aluminum melt. When the aluminum melt is cooled, the amount of titanium dissolved in the solid aluminum matrix is limited to the amount of titanium that was dissolved in the liquid (in an amount up to the lower liquid solubility of titanium in liquid aluminum). The remaining titanium is present in the Al₃Ti.
In various aspects, the present disclosure provides a method of making an aluminum alloy that includes at least aluminum, titanium, and copper. In certain variations, the present disclosure provides a method of increasing the amount of titanium in aluminum alloys compared to traditional aluminum alloys with titanium. The titanium content is increased by (1) adding titanium to an aluminum melt via a copper-titanium compound, and (2) dissolving titanium in solid state aluminum. In certain aspects, the present disclosure also provides heat treatments to facilitate the formation of desirable precipitates. The resulting alloy includes refined precipitates that may strengthen the alloy by restricting dislocation, facilitating grain refinement, reducing grain growth, and reducing the formation of undesirable precipitate phases.
Dissolving titanium in solid state aluminum increases the amount of titanium in the alloy because the aluminum-titanium system is peritectic. In the peritectic system, the solid solubility of titanium in aluminum is higher than the liquid solubility of titanium in aluminum. Therefore, when titanium is available to dissolve aluminum as it solidifies, the titanium content in the resulting alloy is higher than that of typical aluminum with titanium alloys formed by adding the aluminum-titanium compound to liquid aluminum.
Adding titanium to the aluminum melt via a compound of copper can facilitate solid-state dissolution of titanium in aluminum. More specifically, aluminum also has solubility for copper. Therefore, in the presence of aluminum, the copper-titanium compound decomposes so that the copper can dissolve in the aluminum, thereby releasing both copper and titanium. The resulting titanium is available to dissolve in the aluminum or form compounds with the aluminum.

Binary Aluminum-Titanium System

A greater amount of titanium can be dissolved in solid aluminum than liquid aluminum because the aluminum-titanium system is peritectic. Referring to FIG. 1, an exemplary partial phase diagram 10 is shown that is believed to be representative of a binary aluminum-titanium system. An x-axis 12 represents atomic percent titanium, where 0% is shown at 14 and 1% is shown at 16. A y-axis 18 represents temperature in ° C. A first phase boundary 20 separates a liquid phase 22 from a liquid+solid phase 24. The liquid phase 22 includes liquid aluminum having titanium dissolved therein. The liquid+solid phase 24 includes liquid (i.e., aluminum having titanium dissolved therein) and solid Al₃Ti. A second phase boundary 26 separates a first solid phase 28 and a second solid phase 30. The first solid phase 28 includes solid-solution aluminum having titanium dissolved therein. The first solid phase 28 may be substantially homogeneous. The second solid phase 30 includes solid-solution aluminum (i.e., aluminum having titanium dissolved therein) and Al₃Ti.
The aluminum-titanium system is peritectic. In the peritectic system, the titanium has a higher solubility in solid-phase aluminum than in liquid-phase aluminum. At a peritectic temperature of about 665.4° C., a liquid solubility 34 of titanium in aluminum is about 0.079% by mole (about 0.14% by mass). At the peritectic temperature, a solid solubility 36 of titanium in aluminum is about 0.79% by mole (about 1.39% by mass). Thus, at the peritectic temperature of about 665.4° C., the solid solubility 36 of titanium in aluminum is greater than the liquid solubility 34 of titanium in aluminum.

Binary Aluminum-Copper System

As discussed above, copper is soluble in aluminum. With reference to FIG. 2, an exemplary partial phase diagram 88 is shown that is believed to be representative of a binary aluminum-copper system. A first x-axis 90 represents atomic percent of copper in aluminum, where 0% copper is shown at 91 and 30% copper is shown at 92. A second x-axis 93 represents mass percent of copper in aluminum. A first y-axis 94 represents temperature in ° C. A second y-axis 96 represents temperature in ° F. A first region 98 represents a liquid phase. A second region 100 represents an a phase (i.e., aluminum having copper dissolved therein). A third region 102 represents a θ phase (i.e., (CuAl₂)). A fourth region 104 represents an α+liquid phase. A fifth region 106 represents a θ+liquid phase. A sixth region 108 represents a solid α+θ phase.
A first phase boundary or first liquidus 110 separates the first region 98 and the fourth region 104. A second phase boundary or second liquidus 112 separates the first region 98 and the fifth region 106. A third phase boundary or solidus 114 separates the sixth region 108 from the fourth, first, and fifth regions 104, 98, 106. The first and second phase boundaries 110, 112 (i.e., first and second liquiduses) meet the solidus 114 at a eutectic point 116. A fourth phase boundary 118 separates the second region 100 and the fourth region 104. A fifth phase boundary 120 separates the fifth region 106 and the third region 102. A sixth phase boundary 122 separates the second region 100 and the sixth region 108. A seventh phase boundary 124 separates the third region 102 and the sixth region 108.
A maximum solubility of copper in aluminum 126 occurs where the fourth and sixth phase boundaries 118, 122 meet the third phase boundary 114 (i.e., the solidus). The maximum solubility of copper in aluminum 126 is about 6% by mass. Therefore, when copper is introduced into a pure aluminum melt, the copper dissolves in the aluminum up to about 6% by mass.
Because copper is soluble in aluminum, a copper-titanium compound that is introduced into an aluminum melt may decompose to make copper available for dissolving in the aluminum. The amount of copper-titanium compound that can decompose is dependent upon the solubility of copper in the aluminum melt (which may not be pure aluminum). The copper-titanium compound can decompose until the maximum solubility of copper in the aluminum melt is reached.
The titanium of the copper-titanium compound is also released during decomposition, making it available for dissolving in the aluminum melt and/or forming compounds. The amount of titanium available as a result of the decomposition depends on the specific copper-titanium compound used, as will be discussed in greater detail below.

Binary Titanium-Copper System

The copper-titanium compound can be a binary copper-titanium compound, a copper-titanium-zirconium compound, or a compound including copper, titanium, and other elements. Referring now to FIG. 3, an exemplary partial phase diagram 138 is shown that is believed to be representative of a binary copper-titanium system. A first x-axis 140 represents mass percent copper, where 0% copper is shown at 142 and 100% copper is shown at 144. A second x-axis 146 represents atomic percent copper. A first y-axis 148 represents temperature in ° C. A second y-axis 150 represents temperature in ° F.
A first phase boundary 152 represents a Ti₂Cu intermetallic. A second phase boundary 154 represents a Ti₃Cu₄intermetallic. A third phase boundary 156 represents a Ti₂Cu₃intermetallic. A first region 158 represents a liquid phase. A second region 160 represents a solid β-titanium phase (i.e., titanium having copper dissolved therein). A third region 162 represents a solid α-titanium phase (i.e., titanium having copper dissolved therein. A fourth region 164 represents TiCu. A fifth region 166 represents TiCu₂. A sixth region 168 represents (3TiCu₄. A seventh region 170 represents a solid copper phase (i.e., copper having titanium dissolved therein). An eighth region is shown at 172. Additional phases that are not shown on the phase diagram may also be present, such as Ti₃Cu and various Ti_xCu_1-xamorphous phases, where 0<x<1.
The copper-titanium compound may include one or more of Ti₃Cu, Ti₂Cu, TiCu, Ti₃Cu₄, Ti₂Cu₃, TiCu₂, TiCu₄, and Ti_xCu_1-xamorphous phase, where 0<x<1. The copper-titanium compound can optionally include other elements in addition to copper and titanium. In various aspects, the copper-titanium compound can also include zirconium. More particularly, for certain copper-titanium compounds (e.g., Ti₂Cu), some or all of the titanium can be substituted with zirconium because titanium and zirconium are completely miscible. Therefore, the copper-titanium compound may include, CuTi_yZr_2-y, where 0<y<2. In various aspects, the copper-titanium compound may be crystalline, amorphous, or a metallic glass alloy. The amount of titanium available to be dissolved in the aluminum and/or form compounds is dependent upon the composition of the copper-titanium. As one example, when the copper-titanium compound is Ti₂Cu, two moles of titanium are released for every one mole of copper released.

Example 7% Silicon-0.75% Copper-Aluminum-Titanium System

With reference to FIG. 4, an exemplary isopleth diagram 190 is shown that is believed to be representative of an aluminum-silicon-copper-titanium system. Silicon is held constant at 7% by mass and copper is held constant at 0.75% by mass. An x-axis 192 represents mass percent titanium, wherein 0% titanium is shown at 194 and 10% titanium is shown at 196. A y-axis 198 represents temperature in ° C.
A first region 200 includes liquid and Al₃Ti. The liquid may have copper, silicon, and a small amount of titanium dissolved therein. The typical method of forming an aluminum and titanium alloy by adding an aluminum-titanium master alloy to liquid aluminum is performed within the first region 200. A second region 202 includes Al₃Ti, solid aluminum having copper and titanium dissolved therein, and liquid. A third region 204 includes Al₃Ti, solid aluminum having copper and titanium dissolved therein, and eutectic silicon. A fourth region 206 includes Al₃Ti, Al₂Cu, solid aluminum having copper and titanium dissolved therein, and eutectic silicon. A fifth region 208 includes solid aluminum having copper and titanium dissolved therein and eutectic silicon. The fifth region 208 may be referred to as the “solid solubility region.”
In the fifth region 208, all of the copper and titanium is dissolved in solid aluminum. It may be advantageous to dissolve copper and titanium in the aluminum so that fine precipitates can be formed during heat treatment, as discussed in greater detail below. In various aspects, the Al₃Ti present in the second, third, and fourth regions 202, 204, 206, and the Al₂Cu present in the fourth region 206 may exist as larger, less desirable precipitates. It may therefore be desirable to form an aluminum alloy in the fifth region 208.
Although the diagram 190 includes silicon at 7% by mass and copper at 0.75% by mass, one skilled in the art would appreciate that other copper and silicon compositions can also be used, and silicon may be omitted entirely. Furthermore, other elements in addition to aluminum, silicon, copper, and titanium may be present.

Method of Making an Aluminum and Titanium Alloy

In various aspects, the present disclosure provides a method of making an aluminum alloy containing titanium. The method relies on the tendency of copper-titanium compounds to decompose in the presence of aluminum to make titanium available for dissolving in aluminum and/or forming compounds with aluminum (FIG. 2). The peritectic nature of the aluminum-titanium system facilitates the dissolution of a higher amount of titanium in solid state than would be possible in the liquid state (FIG. 1). The method includes a heat treatment to form fine precipitates from the dissolved titanium and copper.
Referring to FIG. 5, the method begins at 220. At 220, an aluminum melt having a first composition is created. The aluminum melt is transferred to a ladle at 222, and then a casting mold at 224. A copper-titanium compound is added to either the ladle (at 222) or the casting mold (at 224) to form a third composition. At 226, the third composition is solidified. At 228, a heat treatment is performed to facilitate the formation of refined precipitates.

Aluminum Melt

At 220, the aluminum melt having the first composition is brought to a first or pouring temperature of greater than or equal to a liquidus temperature (i.e., melting temperature) of the first composition. In certain variations, the first temperature may be greater than or equal to about 580° C. to less than or equal to about 800° C. (580° C.-800° C.), and optionally greater than or equal to about 650° C. to less than or equal to about 780° C. (650° C.-780° C.). The first composition may be an aluminum alloy that includes other components in addition to aluminum, such as copper, manganese, silicon, magnesium, zinc, and combinations thereof, by way of example. In various aspects, the first composition includes aluminum, silicon, and copper. In alternative aspects, the first composition includes aluminum, silicon, copper, and magnesium.

Addition of Copper-Titanium Compound

A copper-titanium compound having a second composition may be added to the aluminum melt having the first composition to form a third composition. As discussed above, the copper-titanium compound may be a binary copper-titanium compound (e.g., Ti₃Cu, Ti₂Cu, TiCu, Ti₃Cu₄, Ti₂Cu₃, TiCu₂, TiCu₄, and Ti_xCu_1-xamorphous phase, where 0<x<1), a copper-titanium-zirconium compound (e.g., CuTi_xZr_2-x, where 0<x<2), or compounds of copper, titanium, and other elements. In certain aspects, the second composition may include titanium at greater than or equal to about 20% by mole to less than or equal to about 80% by mole (20%-80%), optionally greater than or equal to about 33% titanium by mole to less than or equal to about 75% by mole (33%-75%), optionally greater than or equal to about 40% titanium by mole to less than or equal to about 70% by mole (40%-70%), optionally greater than or equal to about 44% titanium by mole to less than or equal to about 68% by mole (44%-68%), and optionally greater than or equal to about 50% titanium by mole to less than or equal to about 67% by mole (50%-67%). In one example, the second composition includes at least one of Ti₂Cu and TiCu.
In various aspects, the copper-titanium compound may advantageously be added to the aluminum melt as close to solidification as possible, or concurrently with cooling (during solidification). If the copper-titanium compound is added too early, it may decompose due to the solubility of copper in aluminum (both liquid and solid). When the copper-titanium compound decomposes, the titanium may form compounds with aluminum (e.g., Al₃Ti) because of its low solubility in liquid aluminum. As described above, the Al₃Ti may sink to the bottom of the melt and therefore not be well-dispersed for dissolution in the subsequently-solidified aluminum.
Referring to FIGS. 6-7, dissolution estimates of a 5 μm Ti₂Cu particle in liquid aluminum at 700° C. are shown. FIG. 6 depicts an example dissolution plot for titanium 240. The dissolution plot 240 generally shows that it is possible to add a copper-titanium compound to an aluminum melt that does not immediately decompose. An x-axis 242 represents distance in μm. A y-axis 244 represents mass percent titanium. A first curve 246 shows dissolution of titanium at 0 seconds. A second curve 248 shows dissolution of titanium at 10 seconds. A third curve 250 shows dissolution of titanium at 60 seconds.
FIG. 7 depicts an example dissolution plot for copper 260. An x-axis 262 represents distance in μm. A y-axis 264 represents mass percent copper. A first curve 266 shows dissolution of copper at 0 seconds. A second curve 268 shows dissolution of copper at 10 seconds. A third curve 270 shows dissolution of copper at 60 seconds. As shown in the graphs, the copper dissolution is expected to be quicker than the titanium dissolution. Slower dissolution for both titanium and copper would be expected with a larger Ti₂Cu particle.
Returning to FIG. 5, the aluminum melt may be transferred to a ladle at 222 and to a casting mold at 224. The copper-titanium compound may be added to the ladle at 222 or to the casting mold 224. The copper-titanium compound may be in the form of a powder. The powder may be sized such that the copper-titanium compound does not completely decompose in the aluminum melt. Proper particle sizing may be determined through use of dissolution estimates similar to those described above. In various aspects, the powder may define a particle size of greater than or equal to about 1 μm to less than or equal to about 200 μm (1 μm-200 μm), optionally greater than or equal to about 2 μm to less than or equal to about 100 μm (2 μm-100 μm), and optionally greater than or equal to about 5 μm to less than or equal to about 75 μm (5 μm-75 μm).
The powderized copper-titanium compound may be encased in a fourth composition that includes aluminum. In certain aspects, the fourth composition is entirely aluminum. Encasing the copper-titanium compound in aluminum may facilitate better mixing by reducing challenges related to surface tension that would be present without the aluminum. One skilled in the art will appreciate that the copper-titanium compound may be added to the aluminum melt by various other methods. Alternative methods of adding the copper-titanium compound to the aluminum melt include powder injection using an inert gas, ultrasonic vibration, spin dissolution of a powderized conglomerate, and wire injection, by way of example.
The third composition includes the aluminum melt having the first composition and the copper-titanium compound having the second composition (and optionally the fourth composition that encased the copper-titanium compound). As shown in the dissolution charts 240, 260 of FIGS. 6-7, the copper-titanium compound may begin decomposing in the presence of aluminum. When the copper-titanium compound decomposes, the resulting copper may dissolve in the aluminum. The resulting titanium may dissolve in the aluminum (up to the liquid solubility limit, such as the liquid solubility 34 in the binary aluminum-titanium system of FIG. 1) and/or form compounds with aluminum (e.g., Al₃Ti). Thus, the third composition may include liquid aluminum having copper and titanium dissolved therein, the remaining undecomposed copper-titanium compound, compounds of aluminum and titanium (e.g., Al₃Ti), and optionally other elements and compounds from the aluminum melt.

Solidification

The third composition may be cooled and solidified at 226 to form a first solid material. The solidification may include cooling the third composition at a first cooling rate to a second temperature to form the first solid material. In certain embodiments, the first cooling rate is greater than or equal to about 0.01° C./second to less than or equal to about 100° C./second (0.01° C./second-100° C./second), optionally greater than or equal to about 0.01° C. to less than or equal to about 50° C./second (0.01° C./second-50° C./second), optionally greater than or equal to about 0.01° C./second to less than or equal to about 20° C. (0.01° C./second-20° C./second), and optionally about 10° C./second. The second temperature is below the solidus of the system, which varies based on the third composition. In certain variations, the second temperature is less than or equal to about 660° C., optionally less than or equal to about 420° C., and in certain variations, optionally less than or equal to about 200° C. so that the third composition is quenched.
As the third composition is cooled during solidification, the solubility of titanium in aluminum may change and compounds of aluminum and titanium may form. The amount of dissolved titanium may change as the solubility of titanium in the aluminum alloy changes with temperature (see, e.g., FIG. 1). Excess titanium that cannot be dissolved in the aluminum alloy (i.e., titanium above the solid solubility limit in the third composition at the present temperature) may form compounds with aluminum and other components of the aluminum alloy (e.g., Al₃Ti, AlTi, Al₂Ti, AlTi₃, various aluminum-silicon compounds, various aluminum-copper compounds, and various aluminum-titanium-X-Y compounds, where X and Y are other elements that are present in the first composition). In various aspects, these compounds may be referred to as the plurality of aluminum-titanium particles.
In some variations, the aluminum-titanium particles are relatively coarse. For example, the first solid material may include a first matrix including aluminum (referred to as an “aluminum matrix”) having grains and the plurality of aluminum-titanium particles dispersed near grain boundaries. The first aluminum matrix may include dissolved copper and titanium. The aluminum-titanium particles may be relatively coarse, having an average dimension of greater than or equal to about 5 μm to less than or equal to about 500 μm (5 μm-500 μm). In various aspects, larger particles may be less desirable than smaller particles because larger particles are easily avoidable by dislocations and therefore result in alloys having decreased material properties. In certain other variations, no particles or precipitates are formed during the cooling step. The formation and characteristics of particles and precipitates are highly dependent on rate of cooling, second temperature, and the composition. The remaining copper-titanium compound that did not decompose may be present in the first solid material as a plurality of copper-titanium particles.

Heat Treatment

The first solid material may undergo heat treatment at 228 to facilitate the formation of desirable precipitates to change the microstructure of the first solid material. Heat treatments may generally include three types of processes: solutionizing, quenching, and aging. Generally, a material is heated in the solutionizing step to dissolve a solute in a solid material. The solid material is quenched by rapidly lowering its temperature to form a quenched solid that is oversaturated. The quenched solid material is aged to form fine precipitates that enhance the material properties of the alloy. Two alternative exemplary heat treatments are described below (e.g., a five-step heat treatment and a six-step heat treatment). The heat treatment 228 may be the five-step heat treatment, the six-step heat treatment, or another heat treatment. Although the heat treatments are discussed in the context of an aluminum-silicon-copper-titanium system, one skilled in the art will appreciate that other components, some of which can form precipitates, may also be present.
Heat treatments rely on the ability of solutes to dissolve, diffuse, and precipitate during temperature changes. Referring to FIGS. 8-9, dissolution estimates of a 5 μm Ti₂Cu particle in solid aluminum at 500° C. are shown. FIGS. 8-9 generally show that it is possible for titanium and copper to dissolve and diffuse during a 5-hour heat treatment. FIG. 8 depicts an example dissolution plot for titanium 280. An x-axis 282 represents a distance in μm. A y-axis 284 represents mass percent titanium. A first curve 286 shows dissolution of titanium at 0 seconds. A second curve 288 shows dissolution of titanium at 3,600 seconds (1 hour). A third curve 290 shows dissolution of titanium at 18,000 seconds (5 hours). FIG. 9 depicts an example dissolution plot for copper 300. An x-axis 302 represents a distance in μm. A y-axis 304 represents mass percent copper. A first curve 306 shows dissolution of copper at 0 seconds. A second curve 308 shows dissolution of copper at 3,600 seconds (1 hour). A third curve 310 shows dissolution of copper at 18,000 seconds (5 hours).

Five-Step Heat Treatment

An example of the five-step heat treatment is represented schematically in FIG. 10. The partial curves on FIG. 10 are believed to represent material phases for a 7%-silicon-0.75%-copper-aluminum-titanium system (where percentages refer to mass percentages). The bars in FIG. 10 represent example temperature windows for certain heat treatment steps. An x-axis 320 represents temperature in ° C. A y-axis 322 represents mole fraction. A first curve 324 represents a liquid phase. A second curve 326 represents a solid, face-centered cubic (FCC) aluminum phase. A third curve 328 represents a diamond-structured eutectic silicon phase. A fourth curve 330 represents a CuAl₂phase. A fifth curve 332 represents an Al₃Ti phase. The five-step heat treatment includes: (i) solutionizing; (ii) a first quenching; (iii) a first aging to form refined aluminum-titanium precipitates; (iv) a second quenching; and (v) a second aging to form refined aluminum-copper precipitates, as described in greater detail below.

(i) Solutionizing

The first solid material is solutionized to dissolve as much titanium in solid state as possible. Solutionizing involves heating the first solid material to a third temperature 334 and holding the first solid material at the third temperature 334 to form a second solid material. The third temperature 334 may be greater than the second temperature. The third temperature 334 is less than a solidus temperature 335 of the system. However, the third temperature 334 may advantageously be as close to the solidus temperature 335 as possible without exceeding the solidus temperature 335, thereby maximizing the solubility of titanium. In contrast, due to the peritectic reaction, if the third temperature 334 exceeds the solidus temperature 335 and liquid begins to form, the solubility of titanium in the aluminum decreases. By way of example, for the 7%-silicon-0.75% copper-aluminum-titanium system, the third temperature 334 is greater than or equal to about 450° C. to less than or equal to about 570° C. (450° C.-570° C.), optionally greater than or equal to about 480° C. to less than or equal to about 560° C. (480° C.-560° C.) (FIG. 10), and optionally about 530° C. The first solid material may be held at the third temperature 334 for less than or equal to about 48 hours, optionally less than or equal to about 24 hours, optionally greater than or equal to about 2 hours to less than or equal to about 20 hours (2 hours-20 hours), and optionally greater than or equal to about 4 hour to less than or equal to about 8 hours (4 hours-8 hours).
During solutionizing, titanium resulting from the decomposition of the copper-titanium compound is available to be dissolved in the first aluminum matrix. The second solid material may include a second aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), and the copper-titanium particles. The second aluminum matrix may include dissolved titanium and copper. The percentage of dissolved titanium in the second aluminum matrix may be greater in the second aluminum matrix than the first aluminum matrix. The amount of titanium dissolved in the second aluminum matrix may be less than or equal to the solid peritectic composition (e.g., 1.39% by mass for the binary aluminum-titanium system of FIG. 1). By way of example, the solid peritectic composition may be less than or equal to about 1.39% by mass.

(ii) First Quenching

The second solid material may be quenched to lock the titanium in solution, for example, by water or forced air. In various aspects, the term “solution” as used herein describes a solid solvent (i.e., aluminum) having one or more solutes (e.g., titanium, copper, and any other additional solutes that were present in the first composition, such as magnesium) dissolved therein, regardless of whether additional material phases are present. During quenching, the dissolved titanium and copper are locked in solution because they do not have enough time to diffuse out. More specifically, a rapid cooling rate (the “second cooling rate”) is used to cool the second solid material to a fourth temperature. Because of the rapid second cooling rate, the titanium and copper atoms have insufficient time to diffuse to nucleation sites and precipitates do not generally form. Thus, at the fourth temperature, the second aluminum matrix of the second solid material is oversaturated with titanium and copper and is therefore unstable.
The fourth temperature is less than the third temperature 334. The fourth temperature may be greater than or equal to about 20° C. to less than or equal to about 300° C. (20° C.-300° C.), and optionally greater than or equal to about 20° C. to less than or equal to about 160° C. (20° C.-160° C.). The second cooling rate is dependent on part thickness and geometry. In various aspects, the second cooling rate is greater than or equal to about 0.5° C./second to less than or equal to about 150° C./second (0.5° C./s-150° C./s), optionally greater than or equal to about 0.5° C./second to less than or equal to about 100° C./second (0.5° C./s-100° C./s), optionally greater than or equal to about 0.5° C./second to less than or equal to about 60° C./second (0.5° C./s-60° C./s), optionally greater than or equal to about 0.5° C./second to less than or equal to about 40° C./second (0.5° C./s-40° C./s), optionally greater than or equal to about 1° C./second to less than or equal to about 30° C./second (1° C./s-30° C./s), optionally greater than or equal to about 2° C./second to less than or equal to about 20° C./second (2° C./s-200° C./s), and optionally about 10° C./second.

(iii) First Aging

The second solid material may be aged to facilitate the formation of a first plurality of aluminum-titanium precipitates and form a third solid material. The aging may be artificial or natural (i.e., performed at room temperature over a longer period of time than artificial aging). During artificial aging, the second solid material may be brought to a fifth temperature 336 that is greater than the fourth temperature and less than the third temperature 334. Because the dissolved titanium in the second aluminum matrix is unstable, aging can cause at least some of the titanium to come out of solution and form the first plurality of aluminum-titanium precipitates. As shown by the overlap between the fifth temperature 336 and the fifth curve 332, the first plurality of aluminum-titanium precipitates can include Al₃Ti.
The fifth temperature 336 may be greater than the fourth temperature. The fifth temperature 336 may also be greater than a maximum temperature for CuAl₂formation 338 to avoid the formation of coarse CuAl₂precipitates. In various aspects, the fifth temperature 336 may be as low as possible without forming CuAl₂precipitates. Thus, the copper remains in solution rather than coming out of solution to form precipitates. The fifth temperature 336 is greater than or equal to about 350° C. to less than or equal to about 450° C. (350° C.-450° C.), optionally greater than or equal to about 375° C. to less than or equal to about 420° C. (375° C.-420° C.), and optionally greater than or equal to about 380° C. to less than or equal to about 400° C. (380° C.-400° C.) (FIG. 10) for the 7%-silicon-0.75% copper-aluminum-titanium system, by way of example.
The third solid material includes a third aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), the first plurality of aluminum-titanium precipitates (formed during the first aging), and the copper-titanium particles. The third aluminum matrix may have copper and titanium dissolved therein. A percentage of titanium in the third aluminum matrix may be greater than the percentage of titanium in the second aluminum matrix. The aluminum-titanium precipitates formed during the first aging may be finer than the aluminum-titanium particles formed during solidification. Furthermore, the aluminum-titanium precipitates of the first plurality may be dispersed throughout the third aluminum matrix (rather than concentrated near grain boundaries).

(iv) Second Quenching

The third solid material may undergo a second quenching to lock copper in solution. During the second quenching, the third solid material may be cooled to a sixth temperature at a third cooling rate. The sixth temperature may be greater than or equal to about 20° C. to less than or equal to about 200° C. (20° C.-200° C.). The third cooling rate may be similar to the second cooling rate. Quenching may cause the third aluminum matrix to become oversaturated with copper and titanium.

(v) Second Aging

The third solid material may undergo a second aging process to form a fourth solid material (i.e., the aluminum alloy containing titanium) including refined aluminum-copper precipitates (the “plurality of aluminum-copper precipitates”). During the second aging process, the third solid material is heated to a seventh temperature 340. The seventh temperature 340 may facilitate the formation of the refined aluminum-copper precipitates. For the 7%-silicon-0.75% copper-aluminum-titanium system, the aluminum-copper precipitates include CuAl₂. However, the aluminum-copper precipitates may have other compositions in alternative systems. For example, the aluminum-copper precipitates can include Al₅Cu₂Mg₈Si₆, Al₃Cu₂Mg₉Si₇, Al₄CuMg₆Si₇, and/or Al₂CuMg when the first composition includes magnesium. The seventh temperature 340 may be greater than the sixth temperature and less than the fifth temperature 336. By way of example, for the 7%-silicon-0.75% copper-aluminum-titanium system, the seventh temperature 340 is greater than or equal to about 150° C. to less than or equal to about 250° C. (150° C.-250° C.), optionally greater than or equal to about 160° C. to less than or equal to about 220° C. (160° C.-220° C.), and optionally greater than or equal to about 180° C. to less than or equal to about 200° C. (180° C.-200° C.) (FIG. 10).
In certain aspects, the first plurality of aluminum-titanium precipitates may act as nucleation sites for the aluminum-copper precipitates and improve the coarsening resistance of the aluminum-copper precipitates. Additional aluminum-titanium precipitates (a “second plurality of aluminum-titanium precipitates”) may also be formed during the second aging. The aluminum-titanium precipitates of the second plurality may be finer than the aluminum-titanium precipitates of the first plurality. However, in various aspects, the second plurality of aluminum-titanium precipitates may not form at all due to the slow diffusion of titanium at the seventh temperature 340.
The aluminum alloy containing titanium may therefore include the fourth aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), the copper-titanium particles, the first plurality of aluminum-titanium precipitates (formed during the first aging), the plurality of aluminum-copper precipitates (formed during the second aging), and the second plurality of aluminum-titanium precipitates (formed during the second aging). The fourth aluminum matrix may include dissolved copper and titanium. A percentage of dissolved copper and a percentage of dissolved titanium in the fourth aluminum matrix may be less than the percentage of dissolved copper and the percentage of dissolved titanium in the third aluminum matrix.

B. Alternative Six-Step Heat Treatment

An example of the six-step heat treatment is represented schematically in FIG. 11. As in FIG. 10, the partial curves on FIG. 11 are believed to represent the material phases for the 7%-silicon-0.75% copper-aluminum-titanium system, where the first, second, third, fourth, and fifth curves 324, 326, 328, 330, 332 represent the liquid phase, the solid FCC aluminum phase, the diamond-structured eutectic silicon phase, the CuAl₂phase, and the Al₃Ti phase, respectively. The bars in FIG. 11 represent example temperature windows for certain heat treatment steps. An x-axis 350 represents temperature in ° C. A y-axis 352 represents mole fraction. The six-step heat treatment includes: (i) a first solutionizing; (ii) a first quenching; (iii) a first aging to form fine aluminum-titanium precipitates and coarse aluminum-copper precipitates; (iv) a second solutionizing to decompose and dissolve the coarse aluminum-copper precipitates; (v) a second quenching; and (vi) a second aging to form fine aluminum-copper precipitates, as described in greater detail below.

(i) First Solutionizing

The first solutionizing of the six-step heat treatment is similar to the solutionizing of the five-step heat treatment. The first solutionizing therefore involves heating the first solid material to a third temperature 354 and holding the first solid material at the third temperature 354 to form a second solid material. The second solid material may include a second aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), and the copper-titanium particles. The second aluminum matrix may include dissolved titanium and copper. A percentage of dissolved titanium in the second aluminum matrix may be greater than the percentage of dissolved titanium in the first aluminum matrix.

(ii) First Quenching

The first quenching of the six-step heat treatment may be similar to the first quenching of the five-step heat treatment. Thus, the first quenching may include cooling the second solid material to a fourth temperature at a second cooling rate. After the first quenching, the second aluminum matrix may be oversaturated with titanium and copper.

(iii) First Aging

The first aging process may facilitate the formation of a first plurality of aluminum-copper precipitates (e.g., CuAl₂) and a first plurality of aluminum-titanium precipitates (e.g., Al₃Ti). During the first aging process, the second solid material may be heated to a fifth temperature 356 greater than the fourth temperature and less than the third temperature 354 to form a third solid material. By way of example, for the 7%-silicon-0.75% copper-aluminum-titanium system, the fifth temperature 356 is greater than or equal to about 250° C. to less than or equal to about 400° C. (250° C.-400° C.), optionally greater than or equal to about 300° C. to less than or equal to about 380° C. (300° C.-380° C.), and optionally greater than or equal to about 325° C. to less than or equal to about 350° C. (325° C.-350° C.) (FIG. 11).
As indicated by the overlap between the fourth curve 330 and the fifth temperature 356, CuAl₂precipitates can form during the first aging (i.e., the first plurality of aluminum-copper precipitates). Diffusion of copper in aluminum at the fifth temperature 356 is relatively quick, and therefore the aluminum-copper precipitates may be coarse. As discussed above, coarse precipitates may be less desirable than fine precipitates. As indicated by the overlap between the fifth curve 332 and the fifth temperature 356, Al₃Ti precipitates can also form during the first aging (i.e., the first plurality of aluminum-titanium precipitates). Diffusion of titanium in aluminum is slow at the fifth temperature 356, and therefore the aluminum-titanium precipitates of the first plurality may be fine. The third solid material may therefore include a third aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), the plurality of copper-titanium particles, the first plurality of aluminum-copper precipitates (formed during the first aging), and the first plurality of aluminum-titanium precipitates (formed during the first aging). The third aluminum matrix may include dissolved titanium and copper. A percentage of dissolved titanium and a percentage of dissolved copper in the third aluminum matrix may each be less than the respective percentages in the second aluminum matrix.

(iv) Second Solutionizing

The second solutionizing may facilitate decomposition of the first plurality of aluminum-copper precipitates and dissolution of the resulting copper. The third solid material is heated to a sixth temperature 358 to form a fourth solid material. The sixth temperature 358 may be greater than the fifth temperature 356 and less than the third temperature 354. The sixth temperature 358 may be greater than a maximum temperature for CuAl₂formation 360. The sixth temperature 358 may be greater than or equal to about 350° C. to less than or equal to about 500° C. (350° C.-500° C.), optionally greater than or equal to about 375° C. to less than or equal to about 450° C. (375° C.-450° C.), and optionally greater than or equal to about 380° C. to less than or equal to about 420° C. (380° C.-420° C.) (FIG. 11). The second solutionizing may be performed for a shorter duration than the first solutionizing. For example, the second solutionizing may be performed for a duration of greater than or equal to about 15 minutes to less than or equal to about 8 hours (15 minutes-8 hours), optionally greater than or equal to about 30 minutes to less than or equal to about 2 hours (30 minutes-2 hours).
The fourth solid material may include a fourth aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), the plurality of copper-titanium particles, the first plurality of aluminum-copper precipitates (anything remaining that did not decompose and re-dissolve), and the first plurality of aluminum-titanium precipitates (formed during the first aging). The fourth aluminum matrix may have copper and titanium dissolved therein. The fourth aluminum matrix may include a greater percentage of copper and a greater percentage of titanium than the third aluminum matrix.

(v) Second Quenching

The fourth solid material may undergo a second quenching to lock the dissolved copper and titanium in solution. During the second quenching, the fourth solid material may be cooled to a seventh temperature at a third cooling rate. The seventh temperature may be lower than the sixth temperature 358. In various aspects, the seventh temperature may be similar to the fourth temperature and the third cooling rate may be similar to the second cooling rate. The second quenching may cause the fourth aluminum matrix to become oversaturated with copper and titanium.

(vi) Second Aging

The second aging may facilitate the formation refined aluminum-copper precipitates (the “second plurality of aluminum-copper precipitates”) and additional aluminum-titanium precipitates (a “second plurality of aluminum-titanium precipitates”). During the second aging, the fourth solid material may be heated to an eighth temperature 362 greater than the seventh temperature and less than the sixth temperature 358 to form a fifth solid material (i.e., the aluminum alloy containing titanium). The eighth temperature 362 is greater than or equal to about 150° C. to less than or equal to about 250° C. (150° C.-250° C.), optionally greater than or equal to about 180° C. to less than or equal to about 250° C. (180° C.-250° C.), and optionally greater than or equal to about 200° C. to less than or equal to about 225° C. (200° C.-225° C.) (FIG. 11), for the 7% silicon-0.75% copper-aluminum-titanium system, for example.
As indicated by the overlap of the eighth temperature 362 with both the fourth curve 330 and the fifth curve 332, both CuAl₂and Al₃Ti can form. However, because the eighth temperature 362 is lower than the fifth temperature 356, diffusion of both copper and titanium is slower and therefore precipitates formed during the second aging may generally be smaller than precipitates formed during the first aging. More specifically, the aluminum-copper precipitates of the second plurality (formed during the second aging) may be finer than the aluminum-copper precipitates of the first plurality (formed during the first aging). The aluminum-titanium precipitates of the second plurality (formed during the second aging) may be finer than the aluminum-titanium precipitates of the first plurality (formed during the first aging).
The aluminum alloy containing titanium (i.e., the fifth solid material formed during the second aging) may therefore include a fifth aluminum matrix, the plurality of aluminum-titanium particles (formed during solidification), the plurality of copper-titanium particles, the first plurality of aluminum-copper precipitates (formed during the first aging and remaining after the second solutionizing), the first plurality of aluminum-titanium precipitates (formed during the first aging), the second plurality of aluminum-copper precipitates (formed during the second aging), and the second plurality of aluminum-titanium precipitates (formed during the second aging). The fifth aluminum matrix may have copper and titanium dissolved therein. The fifth aluminum matrix may include a lower percentage of copper and a lower percentage of titanium than the fourth aluminum matrix.

The Aluminum-Titanium Alloy

The aluminum alloy containing titanium includes at least aluminum, titanium, and copper. However, the aluminum alloy containing titanium may optionally include other elements, such as zirconium, silicon, manganese, magnesium, zinc, by way of example. In certain variations, the titanium may be present in an amount higher than the solid solubility of titanium (e.g., in particles and precipitates such aluminum-titanium compounds and copper-titanium compounds). For example, the aluminum alloy containing titanium may include greater than 0% titanium by mass to less than or equal to about 10 by mass (0%-10%), optionally greater than or equal to about 0.1% by mass to less than or equal to about 7.5% (0.1%-7.5%), optionally greater than or equal to about 0.1% by mass to less than or equal to about 3% by mass (0.1%-3%), optionally greater than or equal to about 0.15% by mass to less than or equal to about 2% by mass (0.15%-2%), optionally greater than or equal to about 0.2% by mass to less than or equal to about 1.5% by mass (0.2%-1.5%), and optionally greater than or equal to about 0.25% by mass to less than or equal to about 1% by mass (0.25%-1%).
The presence of particles and precipitates allows for titanium concentrations that are higher than its solid solubility. For example, as described above, titanium may be present in the aluminum alloy containing titanium at up to 10% titanium by mass of the aluminum alloy containing titanium. Titanium may be both dissolved within the aluminum matrix and present in various particles and precipitates. More particularly, titanium may be present: (1) dissolved in the aluminum matrix (e.g., the fourth aluminum matrix formed in the five-step heat treatment or the fifth aluminum matrix formed in the six-step heat treatment); (2) as coarse particles (e.g., the plurality of aluminum-titanium particles formed during solidification); (3) as refined precipitates (e.g., the first or second pluralities of aluminum-titanium precipitates formed during an aging process); and/or (4) as copper-titanium particles including the copper-titanium compound. Greater than 0% to less than or equal to about 10% may be collectively present in the (1) aluminum matrix; (2) coarse particles; (3) fine precipitates; and (4) copper-titanium particles. In certain variations, the titanium in the (1) aluminum matrix and (3) fine precipitates may be limited by the solid solubility of titanium in the system (e.g., the peritectic solid solubility of titanium in the aluminum alloy, such as 1.39% by mass in the binary aluminum-titanium system of FIG. 1). Thus, greater than 0% to less than or equal to about 1.39%, optionally greater than or equal to about 0.1% to less than or equal to about 1.39%, optionally greater than or equal to about 0.15% to less than or equal to about 1.39%, optionally equal to about 0.2% to less than or equal to about 1.39%, optionally equal to about 0.25% to less than or equal to about 1.39% titanium, optionally equal to about 0.5% to less than or equal to about 1.39% titanium, and optionally equal to about 0.75% to less than or equal to about 1.39% titanium by mass of the aluminum alloy containing titanium may be cumulatively present in (1) the aluminum matrix and (3) the fine precipitates. The balance of the titanium may be present in (2) the coarse particles and (4) the copper-titanium particles.
In certain variations, the aluminum alloy containing titanium includes copper at greater than or equal to 0.05% by mass to less than or equal to about 10% by mass, optionally greater than or equal to about 0.1% by mass to less than or equal to about 8% by mass, optionally greater than or equal to about 0.1% by mass to less than or equal to about 6% by mass, optionally greater than or equal to about 0.1% by mass to less than or equal to about 5% by mass, optionally greater than or equal to about 0.1% by mass to less than or equal to about 4% by mass, optionally greater than or equal to about 0.1% by mass to less than or equal to about 0.5% by mass, and optionally greater than or equal to about 0.1% by mass to less than or equal to about 0.4% by mass. The aluminum alloy containing copper may include copper and titanium in the above ranges and the balance aluminum and other components of the aluminum alloy (e.g., zirconium, manganese, silicon, magnesium, zinc). The aluminum alloy containing titanium may include aluminum at less than or equal to about 99%, optionally less than or equal to about 98%, optionally less than or equal to about 97%, optionally less than or equal to about 96%, optionally less than or equal to about 95%, optionally less than or equal to about 90%, optionally less than or equal to about 75%, optionally less than or equal to about 70%, and optionally less than or equal to about 65% by mass of the alloy.
The fine precipitates formed during aging are desirably small and distributed throughout the aluminum matrix. Referring to FIG. 12, a correlation particle size and spacing is shown. An x-axis 380 represents particle radius in μm. A y-axis 382 represents mean particle spacing in μm. Particle spacing refers to a distance between centers of particles. A first curve 384 shows a relationship between particle radius and mean particle spacing for 0.1% titanium by mass. A second curve 386 shows a relationship between particle radius and mean particle spacing for 0.2% titanium by mass. A third curve 388 shows a relationship between particle radius and mean particle spacing for 0.4% titanium by mass. FIG. 12 demonstrates that particle size and spacing are interrelated. Therefore, particle size can be optimized to achieve desired spacing.
The fine precipitates formed during aging may have an average diameter of less than or equal to about 500 μm, optionally less than or equal to about 50 μm, optionally less than or equal to about 5 μm, optionally less than or equal to about 1 μm, optionally less than or equal to about 500 nm, and optionally less than or equal to about 200 nm. As one example, the fine aluminum-titanium precipitates (i.e., the first and second pluralities of aluminum-titanium precipitates formed during an aging process) have an average diameter of less than or equal to about 50 μm. The fine aluminum-copper precipitates (i.e., the aluminum-copper precipitates formed during the five-step heat treatment and the second plurality of aluminum-copper precipitates formed during the six-step heat treatment) have an average diameter of less than or equal to about 5 μm. The distribution of the fine precipitates throughout the aluminum matrix may strengthen the aluminum alloy containing titanium by restricting dislocation and/or resisting the growth of other precipitate phases. That is, the fine precipitates may pin the grains of the aluminum matrix so that they do not slip past one another during stress. The fine precipitates may also be advantageous in grain refinement and prevention of grain growth, particularly in wrought alloys. Aluminum alloys containing titanium according to certain aspects of the present disclosure may have grains with an average dimension of less than or equal to about 10 cm, optionally less than or equal to about 1 cm, optionally less than or equal to about 1 mm, optionally less than or equal to about 500 μm, optionally less than or equal to about 200 μm, optionally less than or equal to about 100 μm, and optionally less than or equal to about 10 μm.
The aluminum alloy containing titanium includes an aluminum casting alloy selected from the group consisting of: 2xx series aluminum alloys (e.g., two hundred series aluminum alloys), 3xx series aluminum alloys (e.g., three hundred series aluminum alloys), 4xx series aluminum alloys (e.g., four hundred series aluminum alloys), 5xx series aluminum alloys (e.g., five hundred series aluminum alloys), 7xx series aluminum alloys (e.g., seven hundred series aluminum alloys), and combinations thereof. In certain other variations, the aluminum alloy containing titanium includes a wrought aluminum alloy selected from the group consisting of: 2xxx series aluminum alloys (e.g., two thousand series aluminum alloys), 3xxx series aluminum alloys (e.g., three thousand series aluminum alloys), 4xxx series aluminum alloys (e.g., four thousand series aluminum alloys), 5xxx series aluminum alloys (e.g., five thousand series aluminum alloys), 6xxx series aluminum alloys (e.g., six thousand series aluminum alloys), 8xxx series aluminum alloys (e.g., eight thousand series aluminum alloys), and combinations thereof.
Alloys formed by methods according to certain aspects of the present disclosure may be applicable to various casting processes for a variety of vehicle or automotive components. For example, aluminum alloys containing titanium may be used for cylinder heads and blocks. Alloys formed by the methods according to certain aspects of the present disclosure may also be used for wrought products, such as extrusion billets, extruded rods, tubes, sheets, and forged materials, by way of example.
While exemplary components are described above, it is understood that the inventive concepts in the present disclosure may also be applied to any structural component capable of being formed of a lightweight metal, including those used in vehicles, like automotive applications including, but not limited to, pillars, such as hinge pillars, panels, including structural panels, door panels, and door components, interior floors, floor pans, roofs, exterior surfaces, underbody shields, wheels, storage areas, including glove boxes, console boxes, trunks, trunk floors, truck beds, lamp pockets and other components, shock towers, shock tower cap, control arms and other suspension or drive train components, engine mount brackets, transmission mount brackets, alternator brackets, air conditioner compressor brackets, cowl plates, and the like. The aluminum alloys containing titanium according to the present disclosure may likewise be used in non-automotive applications, such as buildings, windows, aircrafts, pumps, and other mechanical components, by way of example.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

What is claimed is:

1. A method of making an aluminum alloy containing titanium, the method comprising:

heating a first composition comprising aluminum to a first temperature of greater than or equal to a liquidus temperature of the first composition;

adding a second composition comprising a copper-titanium compound to the first composition to form a third composition;

decomposing at least a portion of the copper-titanium compound into copper and titanium;

cooling the third composition to a second temperature less than or equal to a solidus temperature of the third composition to form a first solid material; and

heat treating the first solid material to form the aluminum alloy containing titanium.

2. The method of claim 1, wherein the heat treating the first solid material facilitates a formation of a plurality of aluminum-titanium precipitates as a distinct phase in the aluminum alloy containing titanium.

3. The method of claim 2, wherein the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates have an average diameter of less than or equal to about 500 microns (μm).

4. The method of claim 2, wherein:

the aluminum alloy containing titanium comprises a matrix comprising aluminum, the matrix having titanium dissolved therein; and

a combined amount of titanium in the plurality of aluminum-titanium precipitates and the matrix is greater than or equal to about 0.1% by mass to less than or equal to about 1.39% by mass of the aluminum alloy containing titanium.

5. The method of claim 2, wherein at least a portion of the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates comprises Al₃Ti.

6. The method of claim 1, wherein the heat treating the first solid material facilitates a formation of a plurality of aluminum-copper precipitates as a distinct phase in the aluminum alloy containing titanium.

7. The method of claim 1, wherein the decomposing at least a portion of the second composition and the cooling the third composition are performed concurrently.

8. The method of claim 1, wherein the copper-titanium compound is selected from the group consisting of: Ti₃Cu, Ti₂Cu, TiCu, Ti₃Cu₄, Ti₂Cu₃, TiCu₂, TiCu₄, Ti_xCu_1-x, CuTi_yZr_2-y, and combinations thereof.

9. The method of claim 1, wherein the heat treating the first solid material comprises:

heating the first solid material to a third temperature of less than the solidus temperature of the third composition to form a second solid material;

cooling the second solid material to a fourth temperature of less than the third temperature to form a quenched second solid material;

heating the quenched second solid material to a fifth temperature of greater than the fourth temperature and less than the third temperature to form a third solid material;

cooling the third solid material to a sixth temperature of less than the fifth temperature to form a quenched third solid material; and

heating the quenched third solid material to a seventh temperature of greater than the sixth temperature and less than the fifth temperature to form the aluminum alloy containing titanium.

10. The method of claim 9, wherein:

the fifth temperature is greater than or equal to about 350° C. to less than or equal to about 450° C.; and

the seventh temperature is greater than or equal to about 150° C. to less than or equal to about 250° C.

11. The method of claim 9, wherein:

the cooling the third composition to the second temperature is performed at a first cooling rate of greater than or equal to about 0.1° C./second to less than or equal to about 100° C./second;

the cooling the second solid material to the fourth temperature is performed at a second cooling rate of greater than or equal to about 0.5° C./second to less than or equal to about 150° C./second;

the fourth temperature is greater than or equal to about 20° C. to less than or equal to about 300° C.;

the cooling the third solid material to the sixth temperature is performed at a third cooling rate of greater than or equal to about 0.5° C./second to less than or equal to about 150° C./second; and

the sixth temperature is greater than or equal to about 20° C. to less than or equal to about 200° C.

12. The method of claim 1, wherein the heat treating the first solid material comprises:

heating the third solid material to a sixth temperature of greater than the fifth temperature and less than the third temperature to form a fourth solid material;

cooling the fourth solid material to a seventh temperature of less than the sixth temperature to form a quenched fourth solid material; and

heating the quenched fourth solid material to an eighth temperature of greater than the seventh temperature and less than or equal to the fifth temperature to form the aluminum alloy containing titanium.

13. The method of claim 12, wherein:

the fifth temperature is greater than or equal to about 250° C. to less than or equal to about 400° C.;

the sixth temperature is greater than or equal to about 350° C. to less than or equal to about 500° C.; and

the eighth temperature is greater than or equal to about 150° C. to less than or equal to about 250° C.

14. The method of claim 12, wherein:

the cooling the fourth solid material to the seventh temperature is performed at a third cooling rate of greater than or equal to about 10° C./second to less than or equal to about 100° C./second; and

the seventh temperature is greater than or equal to about 20° C. to less than or equal to about 300° C.

15. The method of claim 1, wherein the aluminum alloy containing titanium comprises titanium at greater than or equal to about 0.15% by mass to less than or equal to about 2% by mass.

16. The method of claim 1, wherein the first composition further comprises at least one of silicon and magnesium.

17. The method of claim 1, wherein the second composition is in the form of a plurality of particles, the plurality of particles at least partially encased in a fourth composition comprising aluminum.

18. The method of claim 1, wherein the aluminum alloy containing titanium comprises an average grain size of greater than or equal to about 10 microns (μm) to less than or equal to about 10 centimeters (cm).

19. An aluminum alloy comprising titanium comprising:

a matrix comprising aluminum;

a plurality of aluminum-titanium precipitates; and

a plurality of aluminum-copper precipitates, wherein the aluminum alloy comprising titanium comprises titanium at greater than or equal to about 0.15% by mass to less than or equal to about 2% by mass and copper at greater than or equal to about 0.05% by mass to less than or equal to about 10% by mass.

20. The aluminum alloy comprising titanium of claim 19, wherein:

at least a portion of the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates comprise Al₃Ti;

the aluminum-titanium precipitates of the plurality of aluminum-titanium precipitates have an average diameter of less than or equal to about 50 microns (μm); and

the aluminum-copper precipitates of the plurality of aluminum-copper precipitates have an average diameter of less than or equal to about 5 microns (μm).