Heat treatment method for injection-molded titanium alloy and high-strength and high-toughness titanium alloy

Abstract

The invention provides a heat treatment method of an injection-molded titanium alloy and a high-strength and high-toughness titanium alloy, and the heat treatment method comprises the following steps: S1, presetting a titanium alloy powder raw material, and carrying out powder injection molding on the titanium alloy powder raw material to obtain a sintered titanium alloy; s2, the sintered titanium alloy is heated to the solid solution temperature in a sintering furnace under vacuum, heat preservation is conducted, then the sintered titanium alloy is cooled to the room temperature, and the titanium alloy subjected to solid solution is obtained; and S3, the titanium alloy subjected to solid solution treatment is heated to the aging temperature in vacuum, heat preservation is conducted, then the titanium alloy is cooled to the room temperature, and the high-strength and high-toughness titanium alloy is obtained. The titanium alloy powder can be prepared through a powder injection molding technology, the high-strength and high-toughness titanium alloy with the density larger than 99.0% and excellent mechanical performance is obtained after heat treatment, the room-temperature tensile strength of the titanium alloy is larger than 1300MPa, the yield strength of the titanium alloy is larger than 1200MPa, and the ductility of the titanium alloy is larger than 6.0%.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy material preparation, and particularly relates to a heat treatment method for injection-molded titanium alloy and a high-strength and high-toughness titanium alloy.

Background Art

[0002] Titanium alloys have the advantages of low density, high specific strength, excellent biocompatibility, good corrosion resistance, etc., and are widely used in the fields of aerospace, biomedicine, ocean engineering, consumer electronics, etc. In recent years, with the rapid development of equipment in high-tech fields, traditional titanium alloys (such as TC4) can no longer meet the requirements of equipment for high strength, so the demand for high-strength and high-toughness titanium alloy materials is becoming stronger and stronger.

[0003] At present, the preparation of high-strength and high-toughness titanium alloys still mainly relies on traditional casting and forging processes, and there is no report on high-strength and high-toughness titanium alloys for powder sintering processes. The main reason is the different microstructures caused by the differences in preparation processes. Under the powder sintering process, fine secondary α phases are not formed, making it impossible to reach the high-strength or ultra-high-strength level. At present, it is urgent to regulate the sintering process and microstructure to effectively prepare high-strength and high-toughness titanium alloys.

[0004] Therefore, it is necessary to study a heat treatment method for injection-molded titanium alloy and a high-strength and high-toughness titanium alloy to address the deficiencies of the existing technology and solve or mitigate one or more of the above problems.

Summary of the Invention

[0005] In view of this, the present invention provides a heat treatment method for injection-molded titanium alloy and a high-strength and high-toughness titanium alloy, aiming to solve the problem that it is difficult to prepare high-strength and high-toughness titanium alloys by the current powder injection molding process.

[0006] On the one hand, the present invention provides a heat treatment method for injection-molded titanium alloy, and the heat treatment method for injection-molded titanium alloy includes the following steps:

[0007] S1: Preset the titanium alloy powder raw material and obtain the sintered titanium alloy through powder injection molding;

[0008] S2: Heat the sintered titanium alloy to the solution temperature under vacuum in a sintering furnace and hold for a certain time, and then cool it to room temperature to obtain the solution-treated titanium alloy;

[0009] S3: Heat the solution-treated titanium alloy to the aging temperature under vacuum and hold for a certain time, and then cool it to room temperature to obtain the high-strength and high-toughness titanium alloy.

[0010] As described above and in any possible implementation manner, a further implementation manner is provided. In S2, the solution temperature is 600-900 °C, and the holding time within the solution temperature range is 1-3 h.

[0011] For the aspects and any possible implementation manners described above, a further implementation manner is provided. In S3, the aging temperature range is 300 to 500 °C; the holding time within the aging temperature range is 1 to 4 h.

[0012] For the aspects and any possible implementation manners described above, a further implementation manner is provided. In S2, the heating rate under the vacuum of the sintering furnace is 8 to 15 °C / min.

[0013] For the aspects and any possible implementation manners described above, a further implementation manner is provided. In S3, the heating rate of the solution-treated titanium alloy under vacuum is 8 to 15 °C / min.

[0014] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The preset titanium alloy powder raw material in S1 includes spherical powder of the Ti-Al-Mo-V-Cr-Fe system.

[0015] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The particle size of the spherical powder is not greater than 53 μm.

[0016] For the aspects and any possible implementation manners described above, a further implementation manner is provided. The oxygen content of the spherical powder is not higher than 1900 ppm.

[0017] For the aspects and any possible implementation manners described above, a further implementation manner is provided. After the sintered titanium alloy in S1 is injection-molded and sintered, a cooling treatment is further performed.

[0018] For the aspects and any possible implementation manners described above, a further implementation manner is provided. A high-strength and high-toughness titanium alloy is obtained by processing the injection-molded titanium alloy through the heat treatment method described above. The high-strength and high-toughness titanium alloy has a relative density greater than 99.0%, a room-temperature tensile strength greater than 1300 MPa, a yield strength greater than 1200 MPa, and an elongation greater than 6.0%.

[0019] Compared with the prior art, the present invention can achieve the following technical effects:

[0020] 1. Realize the high-strength and high-toughness performance of the material through heat treatment. The present invention performs solution + aging heat treatment on the titanium alloy prepared by injection molding under vacuum, precipitates uniformly distributed secondary α phases, regulates the microstructure, and improves the strength.

[0021] 2. Low cost. The present invention performs solution aging heat treatment after sintering and cooling, does not require adding other alloy elements or using other equipment, ensures the high-strength and high-toughness performance while meeting the requirements of batch production, and effectively reduces the production cost.

[0022] 3. Simple process. In the present invention, by adding a heat treatment process only during the injection molding process, without the need for additional processes and equipment, the high strength and high toughness properties of the material are achieved.

[0023] Of course, it is not necessary for any product implementing the present invention to achieve all the above-described technical effects simultaneously.

Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a scanning electron microscope image of the Ti-Al-Mo-V-Cr-Fe series spherical powder used in the embodiments of the present invention.

[0026] Figure 2 It is a physical drawing of the tensile sample used in Example 1 of the present invention.

[0027] Figure 3 It is a SEM metallographic photo of the solution aging treated injection molded high strength and high toughness titanium alloy provided in Example 1 of the present invention.

Detailed Embodiments

[0028] In order to better understand the technical solutions of the present invention, the embodiments of the present invention will be described in detail below with reference to the drawings.

[0029] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0031] The present invention provides a heat treatment method for injection molded titanium alloy, and the heat treatment method for injection molded titanium alloy includes the following steps:

[0032] S1: Preset the titanium alloy powder raw material and inject it through powder injection molding to obtain a sintered titanium alloy;

[0033] S2: Heat the sintered titanium alloy to the solution temperature under vacuum in a sintering furnace, hold the temperature, and then cool it to room temperature to obtain the solution-treated titanium alloy.

[0034] S3: Heat the solution-treated titanium alloy to the aging temperature under vacuum, hold the temperature, and then cool it to room temperature to obtain a high-strength and high-toughness titanium alloy.

[0035] Optionally, in S2, the solution temperature is 600 - 900 °C, and the holding time within this solution temperature range is 1 - 3 h.

[0036] Ordinary solution treatment is carried out above or below the phase transformation point. The solution temperature range selected in this invention is below the phase transformation point.

[0037] When solution treatment is carried out above the phase transformation point, it is easy to cause the growth of β primary grains, reducing the comprehensive mechanical properties of the titanium alloy.

[0038] Therefore, this invention sets an upper limit for the solution temperature based on the phase transformation point. At 600 °C, a large amount of alloying elements diffuse, and a supersaturated solid solution is obtained after rapid cooling; if the solution temperature is set below 600 °C, less supersaturated solid solution is obtained, fewer secondary α phases precipitate during aging, and the strengthening effect is weak.

[0039] When the holding time is less than 1 h, the alloying elements do not have enough time to diffuse, less supersaturated solid solution is obtained, fewer secondary α phases precipitate during aging, and the strengthening effect is weak; when the holding time is more than 3 h, the primary α phase is prone to coarsening, reducing the strength and having an adverse effect on the performance.

[0040] Optionally, in S3, the aging temperature range is 300 - 500 °C; the holding time within this aging temperature range is 1 - 4 h.

[0041] In this invention, since the aging temperature of the titanium alloy is related to the desired properties. Generally, aging at 300 - 500 °C can obtain fine and dispersed needle-like secondary α phases. Although part of the plasticity is lost, it can greatly improve the strength of the titanium alloy; when aging is carried out above 500 °C, the aspect ratio of the obtained secondary α phase becomes smaller, although part of the plasticity is improved, but the strengthening effect on the titanium alloy is greatly weakened.

[0042] When the aging time is less than 1 h, the number of precipitated secondary α phases is insufficient, and a large amount of metastable β phase remains in the matrix, so the strengthening effect is weak; when the aging time is greater than 4 h, the secondary α phase is prone to coarsening, thus reducing the strengthening effect.

[0043] Optionally, in S2, the heating rate under vacuum in the sintering furnace is 8 - 15 °C / min.

[0044] Optionally, in S2, the heating rate under vacuum in the sintering furnace is 10 °C / min.

[0045] Optionally, the heating rate of the solution-treated titanium alloy in step S3 under vacuum is 8-15 °C / min.

[0046] Optionally, the heating rate of the solution-treated titanium alloy in step S3 under vacuum is 10 °C / min.

[0047] The reason for setting the heating rate in the present invention is as follows: When the heating rate is too slow, the titanium alloy stays in the aging temperature range for a long time, which may cause the growth of secondary α phase and affect the strengthening effect. In addition, the overall process time will be longer and the heat treatment efficiency will be lower. When the heating rate is too fast, the temperature difference between the surface and the inside of the titanium alloy is large, and the tissue transformation efficiency is inconsistent, which cannot ensure the uniform dispersion of the precipitated phase, thus affecting the performance.

[0048] Optionally, the preset titanium alloy powder raw material in step S1 includes Ti-Al-Mo-V-Cr-Fe series spherical powder.

[0049] Optionally, the particle size of the spherical powder is not greater than 53 μm.

[0050] Optionally, the oxygen content of the spherical powder is not higher than 1900 ppm.

[0051] Since the degreasing efficiency of spherical powder is higher than that of irregular powder during degreasing, if the degreasing is not complete, it will seriously affect the performance of the sintered titanium alloy; the ultimate loading capacity of spherical powder is higher than that of irregular powder, so it is easier to fill the cavity under the same loading capacity, reducing the possibility of defect formation. When the particle size is too large, it is difficult to be dense during sintering, there are many pores, and the sample is easy to brittle fracture; moreover, the original β grains of the sintered sample with coarse particle size powder are thick, so the strength is low. Too high oxygen content will cause lattice point distortion of titanium and pin the dislocation slip, resulting in embrittlement of the titanium alloy. Therefore, in the present invention, the particle size of the spherical powder is set not greater than 53 μm and the oxygen content is not higher than 1900 ppm.

[0052] After injection molding and sintering, the sintered titanium alloy in step S1 is also subjected to a cooling treatment.

[0053] The present invention also provides a high-strength and high-toughness titanium alloy, which is obtained by treating the injection-molded titanium alloy by the heat treatment method described above. The high-strength and high-toughness titanium alloy has a relative density greater than 99.0%, a room-temperature tensile strength greater than 1300 MPa, a yield strength greater than 1200 MPa, and an elongation greater than 6.0%.

[0054] Comparative Example 1:

[0055] The injection-molded and sintered titanium alloy without heat treatment.

[0056] Example 1:

[0057] A heat treatment process for injection-molded high-strength and high-toughness titanium alloy, comprising the following steps:

[0058] (1) The injection-molded titanium alloy after sintering and cooling is kept in a vacuum state in a sintering furnace;

[0059] (2) Solution heat treatment: Heating to 700 °C at a heating rate of 10 °C / min, holding for 1 h, and cooling to room temperature;

[0060] (3) Aging heat treatment: Heating to 350 °C at a heating rate of 10 °C / min, holding for 2 h, and cooling to room temperature.

[0061] Example 2:

[0062] A heat treatment process for injection-molded high-strength and high-toughness titanium alloy with the furnace, comprising the following steps:

[0063] (1) The injection-molded titanium alloy after sintering and cooling is kept in a vacuum state in a sintering furnace;

[0064] (2) Solution heat treatment: Heating to 750 °C at a heating rate of 10 °C / min, holding for 1 h, and cooling to room temperature;

[0065] (3) Aging heat treatment: Heating to 350 °C at a heating rate of 10 °C / min, holding for 2 h, and cooling to room temperature.

[0066] Example 3:

[0067] A heat treatment process for injection-molded high-strength and high-toughness titanium alloy with the furnace, comprising the following steps:

[0068] (1) The injection-molded titanium alloy after sintering and cooling is kept in a vacuum state in a sintering furnace;

[0069] (2) Solution heat treatment: Heating to 800 °C at a heating rate of 10 °C / min, holding for 1 h, and cooling to room temperature;

[0070] (3) Aging heat treatment: Heating to 350 °C at a heating rate of 10 °C / min, holding for 2 h, and cooling to room temperature.

[0071] Example 4:

[0072] A heat treatment process for injection-molded high-strength and high-toughness titanium alloy with the furnace, comprising the following steps:

[0073] (1) The injection-molded titanium alloy after sintering and cooling is kept in a vacuum state in a sintering furnace;

[0074] (2) Solution heat treatment: Heating to 750 °C at a heating rate of 10 °C / min, holding for 1 h, and cooling to room temperature;

[0075] (3) Ageing heat treatment: Heat to 400 °C at a heating rate of 10 °C / min, hold for 2 h, and cool to room temperature.

[0076] Furthermore, the titanium alloys prepared in Comparative Example 1 and Examples 1-6 were subjected to density testing, mechanical property testing, and metallographic characterization.

[0077] The samples were subjected to density testing. The testing method was carried out in accordance with the national standard GB / T1423-1996 to obtain the test results of the relative density; the samples were subjected to tensile mechanical property testing at room temperature. The testing method was carried out in accordance with the national standard GB / T228.1-2010 to obtain the test results of the tensile strength, elongation, and yield strength; the samples were subjected to metallographic characterization. The characterization specimens were obtained by the following method: The samples were polished with 400, 800, 1500, 2000, 3000, and 5000 mesh sandpapers, and then polished with a PG-1A polishing machine. The samples were wiped and etched with Kroll reagent (hydrofluoric acid: concentrated nitric acid: water volume ratio of 1:3:15) for 30 s. Immediately after corrosion, the samples were placed in an alcohol solution, allowed to stand for 1 min, and then dried with a hair dryer to obtain metallographic specimens, and then characterized with a SU8100 cold field emission scanning electron microscope to obtain SEM images.

[0078] The test results were summarized in Table 1:

[0079] Table 1. Summary of performance parameters of injection-molded high-strength and high-toughness titanium alloys

[0080]

[0081]

[0082] In Comparative Example 1, only under vacuum sintering, the relative density reached 99.4%, the tensile strength was 1160 MPa, the yield strength was 1070 MPa, and the elongation was 12.5%. The strength was lower than that after heat treatment. After heat treatment, the relative density changed little, the strength increased significantly, and the elongation decreased slightly, but was still not less than 6%. Compared with the non-heat-treated titanium alloy, the formation of precipitation phases increased the strength of the material.

[0083] After heat treatment, the relative density of the injection-molded high-strength and high-toughness titanium alloys prepared in Examples 1-4 of the present invention was greater than 99.0%, the room-temperature tensile strength was greater than 1300 MPa, the yield strength was greater than 1200 MPa, and the elongation was greater than 6.0%. The injection-molded titanium alloys prepared by the present invention have excellent mechanical properties.

[0084] The above has introduced in detail a heat treatment method for injection-molded titanium alloy and a high-strength and high-toughness titanium alloy provided by the embodiments of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

[0085] As used in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As mentioned throughout the specification and claims, the terms "comprising" and "including" are open-ended terms, so they should be interpreted as "comprising / including but not limited to". "Substantially" means within an acceptable error range. Those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description in the specification is a preferred implementation manner for implementing the present application, but the description is for the purpose of explaining the general principle of the present application and is not used to limit the scope of the present application. The protection scope of the present application shall be subject to what is defined by the appended claims.

[0086] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a commodity or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such a commodity or system. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the commodity or system including the said element.

[0087] It should be understood that the term "and / or" used herein is only a relationship describing associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0088] The above description shows and describes several preferred embodiments of the present application. However, as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the application concept described herein through the above teachings or the technology or knowledge in the relevant field. And the changes and variations made by those skilled in the art that do not depart from the spirit and scope of the present application should all be within the protection scope of the appended claims of the present application.

Claims

1. A heat treatment method for injection-molded titanium alloy, characterized in that, The heat treatment method of the injection-molded titanium alloy comprises the following steps: S1: Preset the titanium alloy powder raw material and obtain the sintered titanium alloy through powder injection molding; S2: Heat the sintered titanium alloy to the solution temperature under vacuum in a sintering furnace and hold the temperature, then cool it to room temperature to obtain the solution-treated titanium alloy; S3: Heat the solution-treated titanium alloy to the aging temperature under vacuum and hold the temperature, then cool it to room temperature to obtain the high-strength and high-toughness titanium alloy.

2. The heat treatment method of the injection-molded titanium alloy according to claim 1, characterized in that, In S2, the solution temperature is 600-900 °C, and the holding time within the solution temperature range is 1-3 h.

3. The heat treatment method of the injection-molded titanium alloy according to claim 1, characterized in that, In S3, the aging temperature range is 300-500 °C; the holding time within the aging temperature range is 1-4 h.

4. The heat treatment method of the injection-molded titanium alloy according to claim 2, wherein, In S2, the heating rate under vacuum in the sintering furnace is 8-15 °C / min.

5. The heat treatment method of the injection-molded titanium alloy according to claim 3, wherein, In S3, the heating rate of the solution-treated titanium alloy under vacuum is 8-15 °C / min.

6. The heat treatment method of the injection-molded titanium alloy according to claim 1, wherein The preset titanium alloy powder raw material in S1 comprises spherical powder of the Ti-Al-Mo-V-Cr-Fe system.

7. The heat treatment method of the injection-molded titanium alloy according to claim 6, characterized in that, The particle size of the spherical powder is not greater than 53 μm.

8. The heat treatment method of the injection-molded titanium alloy according to claim 6, wherein, The oxygen content of the spherical powder is not higher than 1900 ppm.

9. The heat treatment method of the injection-molded titanium alloy according to claim 1, characterized in that, After injection molding and sintering in S1, the sintered titanium alloy is also subjected to a cooling treatment.

10. A high-strength and high-toughness titanium alloy, characterized in that, The high-strength and high-toughness titanium alloy is obtained by being treated with the heat treatment method of the injection-molded titanium alloy as described in any one of claims 1-9 above. The high-strength and high-toughness titanium alloy has a relative density greater than 99.0%, a tensile strength at room temperature greater than 1300 MPa, a yield strength greater than 1200 MPa, and an elongation greater than 6.0%.

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