CN113462929B - A kind of high-strength and high-toughness α+β type titanium alloy material and preparation method thereof - Google Patents

Abstract

The invention discloses a high-strength and high-toughness α+β type titanium alloy material and a preparation method thereof. The titanium alloy material is composed of metal elements titanium, aluminum and vanadium, and the mass percentage of each metal element is aluminum x %, vanadium y %, and the remainder Titanium, denoted as Ti‑xAl‑yV, where x=7, y=6.2‑7.5; as-cast Ti‑xAl‑yV has a crystal with two phases coexisting with alpha phase of hexagonal close-packed structure and beta phase of body-centered cubic structure structure, the tensile strength is greater than 1100Mpa, and the elongation is not less than 25%. The preparation method of above-mentioned titanium alloy material is as follows: S1, take by weighing titanium particle, aluminum particle, vanadium particle by above-mentioned metal element mass percentage content; S2, put into vacuum induction furnace the titanium particle, aluminum particle, vanadium particle that have taken by weighing , repeatedly inverting and smelting under protective gas to obtain alloy liquid; S3, heat preservation treatment of the obtained alloy liquid in a vacuum induction furnace; S4, casting the heat preservation alloy liquid to obtain an alloy ingot, that is, the preparation is completed. The titanium alloy of the invention has good mechanical properties and high temperature resistance.

Description

A kind of high-strength and high-toughness α+β type titanium alloy material and preparation method thereof

technical field

The invention relates to a high-strength and high-toughness α+β type titanium alloy material and a preparation method thereof, belonging to the technical field of titanium alloy materials.

Background technique

Titanium alloy is an important structural metal developed in the 1950s. Titanium alloy has high strength, good corrosion resistance and high heat resistance. Titanium alloys are mainly used to make aircraft engine compressor parts, followed by rockets, missiles and structural parts of high-speed aircraft. Usually, titanium alloys can be subdivided into α-type titanium alloys, near-α-type titanium alloys, α+β-type titanium alloys, and near-β-type titanium alloys according to the phase composition and the content of β-stabilizing elements after single-zone quenching of titanium alloys. Alloy, beta titanium alloy.

The α+β type titanium alloy has a relatively high content of β stable elements. The structure in the annealed state is composed of α phase and β phase. The content of β phase is in the range of 5.0%-40.0%, and the hardenability is relatively good. It can be strengthened by heat treatment. Because α+β titanium alloy has good thermal stability, high strength and plasticity, it is usually used in high-temperature and high-strength aerospace structural parts. Among them, TC4 titanium alloy (Ti-6Al-4V alloy) material is the most widely used α+β type titanium alloy material. In the aviation industry, TC4 titanium alloy is mainly used as a structural component in baffles, wings, frames, compressor discs, engines, blades, gas cylinders, etc. With the high-precision and small-scale intelligent development of aviation equipment, strict requirements are placed on titanium alloy structural materials for aviation. It needs to have good plasticity while meeting high strength. The existing TC4 titanium alloy can no longer meet the requirements of some application fields. need. Therefore, it is necessary to find new preparation technologies and means to develop high-strength and high-toughness titanium alloy materials that can be mass-produced.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide a high-strength and high-toughness α+β-type titanium alloy material and a preparation method thereof, so as to solve the problem that the comprehensive mechanical properties of traditional titanium alloys need to be improved urgently.

The present invention achieves its object by first providing a high-strength and high-toughness α+β type titanium alloy material, which is composed of metal elements titanium, aluminum and vanadium, and is characterized in that the mass percentage of each metal element in the titanium alloy material is aluminum (Al (Al)) )x%, vanadium (V)y%, the remainder titanium, denoted as Ti-xAl-yV, where x=7, y=6.2-7.5; as-cast Ti-xAl-yV has a hexagonal close-packed structure (HCP ) α-phase and body-centered cubic (BCC) β-phase dual-phase coexisting crystal structure, the tensile strength is greater than 1100MPa, and the elongation is not less than 25%.

Further, the mass percentage y% of vanadium in the titanium alloy material of the present invention is 6.5%-7%.

Furthermore, the mass percentage of vanadium in the titanium alloy material of the present invention is y%=7%.

In titanium alloys, the α-phase stabilizing element is the element that can stabilize the α-phase and improve the transformation point of the titanium alloy. Al is the most commonly used α-phase stabilizing element in various titanium alloys, and the β-phase stabilizing element can stabilize the β-phase. , V, Mo, and Nb are relatively common β-phase stable elements. In the prior art, the element design of titanium alloy mainly considers Mo equivalent, and the performance of the designed titanium alloy cannot meet the needs of some application fields. The present invention mainly considers the synergistic effect of the α phase and the β phase of the titanium alloy in the composition design of the titanium alloy. On the basis that the content of the α phase stabilizing element Al is increased to 7%, the content of the corresponding component β isomorphous element is designed according to the synergistic effect, and the β phase is adjusted. The mass fraction of isomorphic elements is up to 6.2%-7.5%, so that the titanium alloy has a dual-phase coexistence crystal structure composed of α-phase of close-packed hexagonal structure (HCP) and β-phase of body-centered cubic structure (BCC) in the as-cast state, The technical effect of tensile strength greater than 1100MPa and elongation not less than 25% has been achieved. The design principle and beneficial effect of element proportioning of the present invention are specifically analyzed below:

1. The present invention changes the content of α-stabilizing element aluminum and β-stabilizing element vanadium on the basis of traditional Ti6Al4V titanium alloy, adjusts the content of α-phase and β-phase in the titanium alloy, and changes the microphase structure and content of the alloy system, so that titanium In the as-cast state, the alloy has a dual-phase coexistence crystal structure composed of α-phase of hexagonal close-packed structure (HCP) and β-phase of body-centered cubic structure (BCC), and the fractional content of β-phase is increased, and the content of β-phase increases. The gradual refinement of the two phases of the alloy system increases the degree of intersection of the two phases, the distribution of the two phases is more uniform, and the grain size and residual stress are also reduced accordingly, which is beneficial to improve the mechanical properties of the alloy material.

Second, the present invention is based on the traditional Ti6Al4V titanium alloy, by increasing the content of α stable element (aluminum element), the temperature range of α phase is increased, and more α phase is obtained, and α phase itself has excellent high temperature performance, Therefore, the titanium alloy prepared by the present invention has excellent high temperature performance stability.

3. The present invention achieves the effect of regulating the phase composition and phase boundary distribution by reasonably optimizing the alloy composition elements; further, by reducing the stacking fault energy of the alloy system, the number of defects such as stacking faults in the alloy is increased, and the local alloy is reduced. stress, so as to achieve the effect of homogenizing the structure and refining the grains, which can significantly improve the mechanical properties of the alloy material.

The present invention achieves its purpose and also provides a method for preparing the above-mentioned high-strength and high-toughness α+β-type titanium alloy material, the steps of which are as follows:

S1, weigh titanium particles, aluminum particles, vanadium particles by the mass percentage content of each metal element in the Ti-xAl-yV titanium alloy material;

S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace, and fill it with a protective gas, and repeatedly turn and smelt under the protective gas to obtain an alloy liquid; During the process, the current of the vacuum induction furnace is kept between 200-250A, and the voltage is kept between 14-16V;

S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 15～20min, and the heat preservation temperature is 1700～1750℃;

S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of a high-strength and high-toughness α+β-type titanium alloy is completed.

Compared with the prior art, the beneficial effects of the above preparation method are: the as-cast titanium alloy prepared by the above preparation method in combination with the ratio of alloy elements, the crystal structure of the two-phase coexistence in the alloy is stable, the structure is uniform without segregation, and the two-phase structure is uniformly distributed. , the grain size and residual stress are small, the stacking fault energy of the alloy system is low, and the local stress of the alloy is low. The tensile strength of the finally prepared as-cast titanium alloy is greater than 1100 MPa, the elongation is not less than 25%, and has good mechanical properties and high temperature resistance. In addition, the above preparation method has the advantages of simple process, low cost, safety and reliability, and can realize large-scale industrial application.

Further, the purity of the titanium particles, aluminum particles, and vanadium particles weighed in step S1 of the present invention all satisfy that the mass percentage is greater than 99.99%.

Further, in the process of repeatedly inverting and smelting under the protective gas in step S2 of the present invention, the number of inversions is 4 to 6 times.

Further, in the process of repeatedly inverting and smelting under the protective gas in step S2 of the present invention, the protective gas is argon with a purity greater than 99.99%.

The present invention will be further described in detail below through specific embodiments and accompanying drawings.

Description of drawings

Fig. 1 is the optical microscope image of the titanium alloy material prepared by the comparative example of the present invention.

FIG. 2 is an optical microscope view of the titanium alloy material prepared in Example 1 of the present invention.

FIG. 3 is an optical microscope view of the titanium alloy material prepared in Example 2 of the present invention.

FIG. 4 is an EBSD image of the titanium alloy material prepared by the comparative example of the present invention.

5 is an EBSD diagram of the titanium alloy material prepared in Example 1 of the present invention.

6 is an EBSD diagram of the titanium alloy material prepared in Example 2 of the present invention.

7 is a bar graph showing the hardness of the titanium alloy materials prepared in Comparative Example, Example 1 and Example 2 of the present invention.

8 is a tensile stress-strain curve diagram of the titanium alloy materials prepared in Comparative Example, Example 1 and Example 2 of the present invention.

Detailed ways

Comparative ratio

A titanium alloy material is composed of metal elements titanium, aluminum and vanadium. The mass percentage of each metal element in the titanium alloy material is aluminum (Al) 6%, vanadium (V) 4%, and the balance titanium is recorded as Ti- 6Al-4V;

The preparation method steps of the Ti-6Al-4V titanium alloy material are as follows:

S1. Weigh titanium particles, aluminum particles, and vanadium particles according to the mass percentage content of 90% titanium, 6% aluminum, and 4% vanadium, and the purity of the weighed titanium particles, aluminum particles, and vanadium particles all satisfy that the mass percentage is greater than 99.99%. .

S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace to a vacuum degree of 6.58×10 ^-3 Pa, and then fill it with argon gas, and the purity is greater than 99.99%. Under the protection of argon gas, the alloy liquid is obtained by repeated inversion and smelting; during the process of repeated inversion and smelting, the current of the vacuum induction furnace is kept between 200 and 220A, the voltage is kept at 14V, and the number of inversions is 6 times, so that the alloy composition is uniform;

S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 15min, and the heat preservation temperature is 1720°C;

S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of the titanium alloy is completed.

Example 1

A high-strength and high-toughness α+β-type titanium alloy material is composed of metal elements titanium, aluminum and vanadium. The mass percentage of each metal element in the titanium alloy material is aluminum (Al) 7%, vanadium (V) 6.5%, and the rest The amount of titanium is recorded as Ti-7Al-6.5V;

The preparation method steps of the Ti-7Al-6.5V titanium alloy material are as follows:

S1. Weigh titanium particles, aluminum particles, and vanadium particles according to the mass percentage content of titanium 86.5%, aluminum 7%, and vanadium 6.5%, and the purity of the weighed titanium particles, aluminum particles, and vanadium particles all satisfy that the mass percentage is greater than 99.99%. .

S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace to a vacuum degree of 6.58×10 ^-3 Pa, and then fill it with argon gas, and the purity is greater than 99.99%. Under the protection of argon gas, the alloy liquid is obtained by repeated inversion and smelting; during the process of repeated inversion and smelting, the current of the vacuum induction furnace is kept between 200 and 220A, the voltage is kept at 14V, and the number of inversions is 6 times, so that the alloy composition is uniform;

S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 15min, and the heat preservation temperature is 1720°C;

S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of a high-strength and high-toughness α+β-type titanium alloy is completed.

Example 2

A high-strength and high-toughness α+β-type titanium alloy material is composed of metal elements titanium, aluminum and vanadium. The mass percentage of each metal element in the titanium alloy material is aluminum (Al) 7%, vanadium (V) 7%, and the rest The amount of titanium is recorded as Ti-7Al-7V;

The preparation method steps of the Ti-7Al-7V titanium alloy material are as follows:

S1. Weigh titanium particles, aluminum particles, and vanadium particles according to the mass percentage content of 86% titanium, 7% aluminum, and 7% vanadium, and the purity of the weighed titanium particles, aluminum particles, and vanadium particles all satisfy that the mass percentage is greater than 99.99%. .

S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace to a vacuum degree of 6.58×10 ^-3 Pa, and then fill it with argon gas, and the purity is greater than 99.99%. Under the protection of argon gas, the alloy liquid is obtained by repeated inversion and smelting; during the process of repeated inversion and smelting, the current of the vacuum induction furnace is kept between 200 and 220A, the voltage is kept at 14V, and the number of inversions is 6 times, so that the alloy composition is uniform;

S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 15min, and the heat preservation temperature is 1720°C;

S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of a high-strength and high-toughness α+β-type titanium alloy is completed.

The titanium alloy materials prepared in the comparative example, Example 1 and Example 2 were cut into corresponding samples according to the test and characterization requirements by using the wire electric discharge cutting technology, and the microstructure characterization and performance test were carried out after grinding and cleaning.

Microstructure characterization: Phase composition analysis and microstructure characterization of titanium alloy materials were carried out by X-ray diffractometer (XRD PANalytical), optical microscope (OM ZEISS) and electron backscatter diffractometer, respectively. Among them, the electron backscattering analysis was carried out using ZEISS Auriga field emission scanning electron microscope combined with Bruker EBSD probe to analyze the phase distribution and phase distribution of the alloy.

Performance test: Vickers hardness test was performed on the surface of the cut alloy samples by a hardness tester (HVS-1000B), and tensile properties of the cut samples were tested by a universal tensile testing machine (Instron 5960).

FIG. 1 , FIG. 2 , and FIG. 3 are optical microscope images of titanium alloy materials prepared in Comparative Example, Example 1, and Example 2, respectively. It can be seen from the optical microscope images that, compared with the comparative example, the degree of intersection of the two phases in the titanium alloy material increases, the distribution of the two-phase structure is more uniform and fine, the large α-phase disappears, and the α-phase structure The distribution is more uniform and fine, and the β phase is finely distributed. Moreover, with the increase of the content of β-stabilizing element V element, the distribution of α-phase structure in the structure is more uniform and fine.

Figure 4, Figure 5, Figure 6 are the EBSD images of the titanium alloy materials prepared in Comparative Example, Example 1, and Example 2, respectively. It can be seen from the figures that there are α-phase and BCC of HCP structure in the three titanium alloy materials. β phase of the structure. ZEISS Auriga type field emission scanning electron microscope combined with Bruker EBSD probe was used to analyze the phase distribution and comparative calculation of titanium alloy materials prepared in Comparative Example, Example 1 and Example 2. The HCP structure in the titanium alloy materials prepared in Comparative Example was analyzed. The content of α phase is 99.8%, the content of β phase of BCC structure is 0.218%, the content of α phase of HCP structure in the titanium alloy material prepared in Example 1 is 98.7%, and the content of β phase of BCC structure is 1.305%, Example 2 The α-phase content of the HCP structure in the prepared titanium alloy material is 97.8%, and the β-phase content of the BCC structure is 2.24%. It is beneficial to the improvement of the strength and plasticity of the alloy.

FIG. 7 is a bar graph showing the hardness of the titanium alloy materials prepared in Comparative Example, Example 1 and Example 2. FIG. The hardness of the titanium alloy material of the comparative example is 330HV, the hardness of the titanium alloy material of Example 1 is 372HV, and the hardness of the titanium alloy material of Example 2 is 380HV. Refinement leads to a denser phase structure and an increase in hardness.

FIG. 8 is a tensile stress-strain curve diagram of the titanium alloy materials prepared in Comparative Example, Example 1 and Example 2. FIG. The tensile strength value of the titanium alloy material of the comparative example is 975Mpa and the elongation is 21%. The tensile strength value of the titanium alloy material of Example 1 is 1150Mpa and the elongation rate is 26%. The tensile strength value of the titanium alloy material of Example 2 It is 1118Mpa and the elongation is 27%. The titanium alloy materials of Example 1 and Example 2 have higher strength and elongation than the traditional Ti6Al4V titanium alloy (comparative example).

Example 3

A high-strength and high-toughness α+β-type titanium alloy material is composed of metal elements titanium, aluminum and vanadium. The mass percentage of each metal element in the titanium alloy material is aluminum (Al) 7%, vanadium (V) 7.5%, and the rest The amount of titanium is recorded as Ti-7Al-7.5V;

The preparation method steps of the Ti-7Al-7.5V titanium alloy material are as follows:

S1. Weigh titanium particles, aluminum particles, and vanadium particles according to the mass percentage content of titanium 85.5%, aluminum 7%, and vanadium 7.5%, and the purity of the weighed titanium particles, aluminum particles, and vanadium particles all satisfy that the mass percentage is greater than 99.99%. .

S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace to a vacuum degree of 6.58×10 ^-3 Pa, and then fill it with argon gas, and the purity is greater than 99.99%. Under the protection of argon gas, the alloy liquid is obtained by repeated inversion and smelting; during the process of repeated inversion and smelting, the current of the vacuum induction furnace is kept between 220 and 250A, the voltage is kept at 16V, and the number of inversions is 4 times, so that the alloy composition is uniform;

S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 20min, and the heat preservation temperature is 1700°C;

S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of a high-strength and high-toughness α+β-type titanium alloy is completed.

Example 4

A high-strength and high-toughness α+β-type titanium alloy material is composed of metal elements titanium, aluminum and vanadium. The mass percentage of each metal element in the titanium alloy material is aluminum (Al) 7%, vanadium (V) 6.2%, and the rest The amount of titanium is recorded as Ti-7Al-6.2V;

The preparation method steps of the Ti-7Al-6.2V titanium alloy material are as follows:

S1. Weigh titanium particles, aluminum particles, and vanadium particles according to the mass percentage contents of titanium 86.8%, aluminum 7%, and vanadium 6.2%. The purity of the weighed titanium particles, aluminum particles, and vanadium particles all satisfy the mass percentage greater than 99.99%. .

S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace to a vacuum degree of 6.58×10 ^-3 Pa, and then fill it with argon gas, and the purity is greater than 99.99%. Under the protection of argon gas, the alloy liquid is obtained by repeated inversion and smelting; during the process of repeated inversion and smelting, the current of the vacuum induction furnace is kept between 220 and 240A, the voltage is kept at 15V, and the number of inversions is 5 times, so that the alloy composition is uniform;

S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 16min, and the heat preservation temperature is 1750°C;

S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of a high-strength and high-toughness α+β-type titanium alloy is completed.

Claims (5)

1. A high-strength and high-toughness α+β-type titanium alloy material, consisting of metal elements titanium, aluminum, and vanadium, is characterized in that, in the titanium alloy material, the mass percentages of each metal element are aluminum x%, vanadium y%, and the remainder The amount of titanium is denoted as Ti-xAl-yV, where x=7, y=6.5-7; as-cast Ti-xAl-yV has a dual phase coexistence of α phase with a close-packed hexagonal structure and β phase with a body-centered cubic structure crystal structure, the tensile strength is greater than 1100MPa, and the elongation is not less than 25%; The preparation method of the high-strength and high-toughness α+β type titanium alloy material is as follows: S1, weigh titanium particles, aluminum particles, vanadium particles by the mass percentage content of each metal element in the Ti-xAl-yV titanium alloy material; S2. Put the weighed titanium particles, aluminum particles, and vanadium particles into a vacuum induction furnace, vacuumize the vacuum induction furnace, and fill it with a protective gas, and repeatedly turn and smelt under the protective gas to obtain an alloy liquid; During the process, the current of the vacuum induction furnace is kept between 200-250A, and the voltage is kept between 14-16V; S3, the obtained alloy liquid is subjected to heat preservation treatment in a vacuum induction furnace, the heat preservation time is 15～20min, and the heat preservation temperature is 1700～1750℃; S4, casting the alloy liquid after heat preservation to obtain an alloy ingot, that is, the preparation of a high-strength and high-toughness α+β-type titanium alloy is completed. 2 . The high-strength and high-toughness α+β type titanium alloy material according to claim 1 , wherein the mass percentage of vanadium in the titanium alloy material is y%=7%. 3 . 3. A kind of high-strength and high-toughness α+β-type titanium alloy material according to claim 1, characterized in that: the purity of the titanium particles, aluminum particles, and vanadium particles weighed in the step S1 all satisfy that the mass percentage is greater than 99.99 %. 4 . The high-strength and high-toughness α+β type titanium alloy material according to claim 1 , wherein in the process of repeatedly inverting and smelting in the step S2 under protective gas, the number of inversions is 4 to 6 times. 5 . 5. A high-strength and high-toughness α+β-type titanium alloy material according to claim 1, characterized in that: in the process of repeated inversion smelting in step S2 under protective gas, the protective gas is argon with a purity greater than 99.99% gas.

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