US3753702A

US3753702A - Particulate zinc alloys

Info

Publication number: US3753702A
Application number: US00122509A
Authority: US
Inventors: S Radtke; J Lund
Original assignee: International Lead Zinc Research Organization Inc
Current assignee: International Lead Zinc Research Organization Inc
Priority date: 1971-03-09
Filing date: 1971-03-09
Publication date: 1973-08-21
Anticipated expiration: 1990-08-21

Abstract

Zinc base particulate alloys exhibiting both high tensile strength and high ductility, and containing titanium uniformly dispersed throughout the zinc matrix, with the zinc alloy having the form of small particles prepared by a melt-fragmentation process, such as atomisation or shotting. The zinc alloy may also contain small amounts of other metals, such as chromium, nickel and aluminum.

Description

United States Patent [191 Radtke et al.

[451 Aug. 21, 1973 PARTICULATE ZINC ALLOYS Inventors: Schrade F. Radtke, New Canaan,

Conn.; John A. Lund, Vancouver, British Columbia, Canada International Lead Zinc Research Organization, Inc., New York, NY.

Filed: Mar. 9, 1971 Appl. No.: 122,509

Related US. Application Data Continuation of Ser. No. 651,676, July 7, 1967, abandoned.

Assignee:

US. Cl. 75/178 R, 75/178 A Int. Cl. C22c 17/00 Field of Search 75/178 R, 178 A References Cited UNITED STATES PATENTS 9/1970 Foerster 75/178 A Primary Examiner-L. Dewayne Rutledge Assistant Examiner-E. L. Weise Attorney-Brumbaugh, Graves, Donohue & Raymond [5 7] ABSTRACT Zinc base particulate alloys exhibiting both high tensile strength and high ductility, and containing titanium 4 Claims, No Drawings PARTICULATE ZINC ALLOYS This is a continuation of application Ser. No. 651,676, filed July 7, 1967, now abandoned.

This invention relates to zinc base alloys, and more particularly to zinc base alloys in particulate form containing titanium and other metals, and a process for preparing them.

For many years practitioners in the art have attempted to prepare zinc base alloys exhibiting properties of both high tensile strength for casting and high ductility for forming and drawing. It is known that titanium forms alloys with zinc which exhibit high tensile strength for casting purposes. It is also known that zinc may be alloyed with titanium in such a manner as to form an alloy with high ductility capable of being easily drawn and formed. No method is known, however, to prepare a zinc-titanium alloy exhibiting both properties together.

The known methods of alloying zinc with titanium have required the inclusion of copper in the alloy to create a satisfactory dispersion of the titanium in the zinc matrix. Heretofore, those zinc-titanium alloys prepared without copper have had notably poor yield strength and ductility.

Furthermore, known zinc-titanium alloys exhibit low creep resistance, and the matrix grain coarsens noticeably when the alloy is heated. The coarsening of the grain results in lowered ductility and tensile strength. in addition, known zinc-titanium alloys have a high transition temperature, below which the deformation behavior of the alloy changes from ductile to brittle. The relatively large grain size of the known zinc-titanium alloys causes the alloys to become rapidly brittle as the temperature is lowered.

It is therefore an object of this invention to prepare a particulate zinc base alloy with titanium which exhibits high tensile and yield strengths and at the same time a high degree of ductility, and which does not require the presence of copper in the alloy. It is also an object of this invention to prepare a zinc base alloy containing titanium and other metal additives, such as chromium, nickel and aluminum, which exhibits both high ductility and high tensile strength. It is a further objective of this invention to prepare zinc base alloys with titanium and other metals, having a fine matrix grain and exhibiting the properties of high creep resistance, high resistance to grain coarsening when subjected to heat treatments, and having a notably low transition temperature from ductile to brittle deformation behavior.

.A particulate zinc-titanium alloy having the desired properties may be prepared according to the invention by the following process: An amount of zinc is heated to its molten state and approximately 0.02 to 1.5 percent by weight of titanium is added to the molten zinc. The resulting alloy melt is fragmented and rendered particulate by any appropriate melt-fragmentation process, such as atomisation or shotting. The average particle size should be less than 0.1 inch in diameter and is preferably less than 0.01 inch in diameter. For preparing a coarser particulate material of average particle size 0.] inch or greater approximately 0.02 to 0.5 percent by weight of titanium should be added to the molten zinc and the resultant melt fragmented.

in particulate material produced by fragmenting an alloy melt to grain size of the matrix phase is inherently fine because of the rapid solidification of the melt fragments. Beyond its limit of solid solubility in zinc, titanium is present as very fine grains of a zinc-titanium intermetallic compound dispersed in the matrix phase. The fine grain intermetallic compound tends to restrict or to prevent the growth of the grains in the matrix phase during subsequent mechanical or thermal treatment of the alloy particles. Since a fine matrix grain size is associated with high alloy ductility, the presence of titanium in excess of its solid solubility in zinc gives particulate zinc alloys a high and relatively stable ductility. In addition, products made from such particulate alloys by known processes such as compaction, rolling,

, extrusion or combinations thereof, will also possess these desirable properties;

At higher levels of titanium content in these zinc alloys, the amount of the intermetallic compound is sufficient to provide strengthening of the matrix phase at ambient, elevated, and sub-normal temperatures. The strengthening effect of the intermetallic compound is greater for finer dispersions of the compound. A finer dispersion is assured by very rapid solidification of the alloy, as in making particulate material by known meltfragmentation processes. The particulate alloys, or products made from them by suitable known compaction and working processes, thereby have high strength properties. The advantage of the alloys described herein is that the dispersion of zinc-titanium compound is extremely sensitive to rate of solidification. It is therefore possible with these alloys to obtain very appreciable amounts of strengthening in particulate forms, or in forms derived from the particles produced by melt-fragmentation.

The combination of high yield strength, high creep strength, and high ductility demonstrated by the products of this invention is greatly improved over that previously obtainable from known zinc alloys in cast form or exhibited by known conventional wrought zinc alloys.

Other metals may be added to the zinc-titanium alloys to enhance the properties of the alloy as recited above and to improve other characteristics. In particular, chromium, nickel or aluminum may be advantageously added to the alloy, although other metals ma be employed. 1

Preparation of a particulate zinc-titanium-chromium alloy may be undertaken by adding approximately 0.02 to 1.5 percent by weight of titanium plus 0.01 to 0.5 percent by weight of chromium to molten zinc. The resulting liquid solution of chromium and titanium in zinc is then melt-fragmented by appropriate means to yield a solid powder. In addition to the desirable characteristics of high strength and high ductility, the combination of titanium and chromium in a zinc-alloy, above their solid'solubility limits in zinc gives dispersions of fine grains of binary and/or ternary intermetallic compounds which are very resistant to coarsening when the particulate forms, or forms derived from the particles, are heated. I

Nickel may be added to the zinc-titanium alloy. A particulate zinc-titanium-nickel alloy is prepared according to the invention by adding approximately 0.02 to 1.5 percent by weight of titanium plus 0.1 to 3.5 percent by weight of nickel to molten zinc. The resultant liquid solution is then melt-fragmented to form a solid powder.

The zinc-titanium-nickel alloy exhibits properties set forth for both the zinc-titanium alloy and the zinc-- titanium-chromium alloy. in addition, the high ductility and creep resistance, particularly creep resistance at elevated temperature, are maintained at the same levels after thermal treatments. The reason is that the binary and/or ternary intermetallic compounds, formed when both nickel and titanium are present in the zinc alloy, above their limits of solid solubility in zinc, appear to have a very strong tendency to remain at matrix grain boundaries even at temperatures high enough to cause substantial coarsening of the compound grains.

It is also within the contemplation of this invention to prepare particulate alloys of zinc, titanium and aluminum. These are prepared according to the invention by adding approximately 0.2 to 1.5 percent by weight titanium and 0.3 to 6.0 percent by weight aluminum to molten zinc. The resultant liquid solution is meltfragmented to yield a solid powder which has the same properties as the zinc-titanium-chromium alloys described above, including the binary and/or ternary intermetallic compounds.

The presence of aluminum in combination with titanium in particulate zinc alloys makes it possible to alter the mechanical and creep resistant properties of the alloy by heat treatment. A particulate zinc-titaniumaluminum alloy has a very high ductility which is desirable for purposes of drawing and forming. The high ductility can be maintained in other forms obtained from the particulate form. An object which is readily fabricated from this particulte alloy in its ductile condition can then be strengthened appreciably by a final heat treatment. The heat treatment is particularly beneficial in respect to control of creep strength.

A transition from ductile to brittle deformation behavior is observed in zinc and all zinc alloys at low temperatures. The temperature at which brittle behavior begins is lower for the finer grain sizes, and depends heavily on composition factors. An advantage of the present invention is that material wrought from particulate zinc-aluminum-titanium alloys has a notably low transition temperature.

The following examples are intended to illustrate the invention only and are not to be considered as defining the scope of the invention:

EXAMPLE I An alloy containing 0.80 weight per cent titanium was prepared by adding an appropriate amount of titanium to molten zinc. The resultant liquid solution of titanium in zinc was air-atomised to obtain a solid powder with a wide range of particle sizes. This powder was screened to obtain a mesh fraction passing through a No. 200 Tyler Screen, but remaining on a No. 325 Tyler Screen. The 200 X 325 fraction was compacted isostatically in rubber bags to obtain cylindrical billets of roughly 1 inch diameter by 3 inches length. The porous billets were then forward-extruded at 400F to obtain dense wire of approximately 0.15 inches diameter. The extruded wire was cooled to ambient temperature (about 70F) and later tested. Tension tests at 70F and at a strain rate of '1 inch per minute gave the following results:

Yield strength (0.2% offset) 43,100 p.s.i.

Ultimate tensile strength 46,600 p.s.i.

Elongation to fracture (in 1 inch) 22.6% The combination of yield strength and elongation (ductility) represented by these results is much improved over that previously available from known zinc alloys in cast forms, or in forms derived from casting. This reflects the characteristic structure of these particulate alloys.

The creep resistance of the particulate zinc 0.80 weight per cent titanium alloy was also studied. At 77F, extruded wire made from the particulate alloy crept at a steady-state rate of 0.5 per cent per year after 3,500 hours under load at a stress of 25,000 p.s.i. This is much higher creep strength than is exhibited by known conventional wrought zinc alloys.

EXAMPLE II An alloy containing 0.21 weight per cent titanium and 0.07 weight per cent chromium in zinc, was prepared by adding appropriate amounts of titanium and chromium to molten zinc. The resulting liquid solution of chromium and titanium in zinc was air-atomised to yield solid powder. A plus 200 mesh, minus 100 mesh (Tyler) screened fraction of the atomised powder was obtained, and was isostatically compacted to zinc billets roughly 1 inch diameter by 3 inches length. The porous billets were extruded at 4l0-430F, to yield 0.15 inch diameter dense wire. This wire was subsequently tested with the following results: Tensile properties (at F and 1.0 inch per inch per minute) I Yield strength (0.2% offset) 63,000 64,400 psi.

Ultimate tensile strength 67,000 p.s.i.

Elongation (in one inch) 8.5 to 9.5%

Creep properties (at 77F) I At 20,000 p.s.i., crept at 0.21 percent per yr. after 3,390 hrs.

At 30,000 p.s.i., crept at 0.76 percent per yr. after 3,280 hrs. This combination of high tensile and creep resistant properties is appreciably better than that of known alloys conventionally processed to wrought material, and is attributable to the characteristic structure of these particulate alloys.

EXAMPLE Ill An alloy containing 0.22 weight per cent titanium and 0.6 percent nickel in zinc was prepared by making appropriate additions to molten zinc. The resultant liquid solution was air-atomised to yield solid powder. A minus 200 plus 325 Tyler mesh fraction of the powder was compacted isostatically to give a billet of about 1 inch diameter and 3 inches length. The porous billet was forward-extruded at 350F to obtain dense wire of 0.15 inches diameter. As-extruded, the properties of the wire were as follows:

Tensile properties at 70F and l inch/inch/min.

Yield Stress (0.2% offset) 25,800 p.s.i.

Ultimate tensile strength 31,100 p.s.i.

Elongation (in 1 inch) 47.5%

Creep properties at 205F. Steady state creep rate, when loaded at 6,000 p.s.i., was 0.25 percent per year after 3,560 hrs. Creep properties at 77F. Steady state creep rate, at 12,000 p.s.i., was 0.05 percent per year after 3,550 hrs. This combination of high creep resistance and high tensile ductility is unusual, and is attributable to the characteristic structure of this particulate alloy.

EXAMPLE lV An alloy containing 0.92 weight per cent aluminum and 0.12 weight per cent titanium in zinc was prepared by making appropriate additions to molten zinc. The resultant liquid solution was air-atomised to yield solid powder. A minus 200, plus 325 Tyler mesh fraction of the powder was compacted isostatically to give a billet of about 1 inch diameter and 3 inches length. This porous billet was forward-extruded at 400F to obtain dense wire of 0.15 inches diameter. As extruded, the wire had the following tensile properties at 70F and 1 inch per inch per minute:

Yield stress (0.2% offset) 7,200 p.s.i.

Ultimate tensile strength 9,600 p.s.i.

Elongation (in 1 inch) 208% These properties reveal the excellent formability of the as-extruded material from particulate alloys, especially at low strain rates. The properties are derived from the characteristic structure of these particulate alloys.

The as-extruded material above was heat-treated by holding it for 30 minutes at 660F, and then air-cooling it. This gave a sharp increase in strength properties at low strain rates, with a corresponding decrease in ductility. However, the strength at higher strain rates was relatively unaffected. Thus, the 660F heat-treatment resulted in much less strain-rate sensitivity of strength. For 660F treated material, the yield stress (0.2 percent offset) varied with strain rate as follows:

0.01 per min. 24,000 p.s.i.

1.0 per min. 28,000 p.s.i.

The as-extruded material also exhibited more than 1O per cent tensile elongation to fracture when tested at We claim:

1. A zinc based particulate alloy having a fine grain matrix, containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of tita nium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy having the form of particles with a maximum average diameter of less than 0.1 inch and exhibiting high ductility and high tensile strength, said alloy consisting essentially of zinc, titanium and 0.1 to 3.5 percent by weight nickel, with said titanium and nickel being dispersed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and nickel above the limits of their solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix.

2. A zinc based particulate alloy having a fine grain matrix, containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of titanium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy having the form of particles with a maximum average diameter of less than 0.1 inch and exhibiting high ductility and high tensile strength, said alloy consisting essentially of zinc, titanium and 0.3 to 6.0 percent by weight alunminum, with said titanium and aluminum being dispersed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and aluminum above the limits of their solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix.

3. A zinc base alloy having a fine grain zinc matrix and capable of being wrought, comprising compacted particles of zinc-titanium alloy, said alloy containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of titanium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy consisting essentially of zinc, titanium and 0.1 to 3.5 percent by weight of nickel, with said titanium and said nickel being dis persed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and nickel above the limits of the solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix.

4. A zinc base alloy having a fine grain zinc matrix and capable of being wrought, comprising compacted particles of zinc-titanium alloy, said alloy containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of titanium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy consisting essentially of zinc, titanium and 0.3 to 6.0 percent by weight of aluminum, with said titanium and said aluminum being dispersed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and aluminum above the limits of the solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix. =0:

Claims

2. A zinc based particulate alloy having a fine grain matrix, containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of titanium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy having the form of particles with a maximum average diameter of less than 0.1 inch and exhibiting high ductility and high tensile strength, said alloy consisting essentially of zinc, titanium and 0.3 to 6.0 percent by weight alunminum, with said titanium and aluminum being dispersed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and aluminum above the limits of their solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix.
3. A zinc base alloy having a fine grain zinc matrix and capable of being wrought, comprising compacted particles of zinc-titanium alloy, said alloy containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of titanium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy consisting essentially of zinc, titanium and 0.1 to 3.5 percent by weight of nickel, with said titanium and said nickel being dispersed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and nickel above the limits of the solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix.
4. A zinc base alloy having a fine grain zinc matrix and capable of being wrought, comprising compacted particles of zinc-titanium alloy, said alloy containing approximately 0.02 to 1.5 percent by weight of titanium and the balance mainly zinc, with fine grains of zinc-titanium intermetallic compound present in said alloy above the solid solubility of titanium in zinc, being dispersed substantially uniformly throughout said fine grain zinc matrix, said alloy consisting essentially of zinc, titanium and 0.3 to 6.0 percent by weight of aluminum, with said titanium and said aluminum being dispersed as fine grain intermetallic compound selected from the group consisting of binary and ternary intermetallic compounds containing titanium and aluminum above the limits of the solid solubility in zinc, substantially uniformly throughout said fine grain zinc matrix.