Method for improving performance of rare earth high-temperature titanium alloy through subzero treatment

Abstract

The invention relates to the technical field of titanium alloys, in particular to a method for improving the performance of a rare earth high-temperature titanium alloy by using subzero treatment, which comprises the following steps: directly carrying out liquid nitrogen subzero treatment on the rare earth high-temperature titanium alloy containing a silicon element in a high-temperature beta-phase region, so that the high-temperature beta-phase is completely reserved to the room temperature; and at the moment, the silicon element in the alloy is completely dissolved in a matrix, and the solid solution degree of the Si element or the precipitation degree of silicide in the alloy is further regulated and controlled in an aging manner. The specific process comprises the following steps: performing liquid nitrogen cooling at the temperature of 990DEG C for 1h, performing air cooling at the temperature of 196DEG C for 1-3h and performing air cooling at the temperature of 650-750DEG C for 1-4h. According to the process, the precipitation degree of silicide in the rare earth high-temperature titanium alloy is regulated and controlled through subzero treatment, so that the high-temperature creep resistance of the rare earth titanium alloy is improved, the creep resistance of the alloy material serving at the temperature of 650 DEG C is excellent, and wide application prospects are achieved.

Description

Technical Field

[0001] One or more embodiments of the present specification relate to the field of titanium alloy technology, and in particular, to a method for improving the performance of rare earth high-temperature titanium alloys by cryogenic treatment. Background Art

[0002] Rare earth high-temperature titanium alloys are widely used in aircraft engine compressor blades and casings. With the rapid development of aerospace in recent years, higher requirements have been placed on the high-temperature resistance of high-temperature titanium alloy components. High-temperature creep resistance is a key performance indicator for evaluating the service reliability of high-temperature titanium alloy materials. Improving the creep resistance of high-temperature titanium alloys is a current research hotspot in the fields of aerospace and other fields. At present, domestic and foreign scholars mainly use high-cost and time-consuming process methods such as rare earth element doping and large plastic deformation to control the distribution of silicides in high-temperature titanium alloys to obtain excellent creep resistance, such as Ti-1100, IMI834, BT36 and Ti600.

[0003] Studies have shown that Si usually exists in high-temperature titanium alloys in the form of solid solution or silicide. Different forms of Si transform into each other under certain conditions, which is the basis for silicide to regulate the performance of titanium alloys. Silicides below the micron level are mainly precipitated by the decomposition of high-temperature residual β phase. Silicides that are incoherent with the titanium matrix prevent dislocations from passing through by slip, and fix the α-lath interface to block grain boundary sliding. The dispersed precipitation of silicides in the titanium alloy matrix pins dislocations during the creep process of the alloy, which can effectively hinder the climb of dislocations and inhibit creep deformation. Therefore, how to achieve the regulation of silicon elements in silicon-containing rare earth high-temperature titanium alloys is of great significance to improving the high-temperature creep resistance and safety of rare earth high-temperature titanium alloys.

[0004] In summary, the present application proposes a method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment to solve the above-mentioned problems. Summary of the invention

[0005] In order to overcome the problems that existing alloys cannot meet the requirements of high creep resistance and safety in use, the purpose of the present invention is to provide a method for improving the performance of rare earth high-temperature titanium alloys by cryogenic treatment. The method uses a simple cryogenic solid solution and subsequent aging treatment to control the precipitation and growth of silicides in the alloy. After treatment, the creep resistance of the rare earth high-temperature titanium alloy at 650°C is greatly improved, and the alloy has broad application prospects.

[0006] Based on the above purpose, one or more embodiments of this specification provide a method for improving the performance of rare earth high temperature titanium alloy by cryogenic treatment, comprising the following steps:

[0007] S1, subjecting the near-α rare earth high-temperature titanium alloy containing Si element to liquid nitrogen deep cryogenic treatment at the β phase transition point;

[0008] S2, after the cryogenic treatment, the β phase is retained to room temperature;

[0009] S3, further heating to achieve β-phase decomposition.

[0010] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the β phase transition point in step S1 is 990°C.

[0011] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the liquid nitrogen used for cryogenic treatment in step S1 is -196°C.

[0012] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the time of the cryogenic treatment in step S1 is 1-3 hours.

[0013] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the titanium alloy sample after the cryogenic treatment in step 1 is taken out, cooled to room temperature, and dried.

[0014] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, in step S3, the temperature is raised to 650° C. to 750° C. to perform β-phase decomposition.

[0015] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the aging time for decomposing the β phase in step S3 is 1-4 hours.

[0016] The method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment according to an embodiment of the present invention also includes step: S4, air cooling, controlling the degree of decomposition of the β phase in the alloy, and then accurately controlling the content of nano-scale precipitated silicide in the alloy.

[0017] According to the above, the present invention has the following beneficial effects:

[0018] (1) After the alloy is cryogenically treated with liquid nitrogen at -196°C, the high-temperature β phase is completely retained to room temperature, and coarse micron-sized primary silicides are dissolved into the matrix.

[0019] (2) The high-temperature titanium alloy after liquid nitrogen cryogenic treatment is further regulated in terms of alloy aging temperature and duration, the precipitation and distribution of silicides are regulated, the fine dispersed silicides are evenly distributed, and the high-temperature creep resistance of the alloy is improved.

[0020] The invention controls the aluminum equivalent value of the alloy material components to ensure the strength of the alloy while avoiding the generation of hard and brittle phases, and adds the rare earth element Sc to the alloy material to change the microstructure of the alloy, and at the same time improves the high-temperature creep resistance of the alloy by regulating the precipitation of silicides in the alloy material, so that the rare earth high-temperature titanium alloy material has good strength at room temperature and 650°C, and the maximum tensile strength and yield strength at room temperature reach 1070MPa and 994MPa respectively, and the maximum tensile strength and yield strength at 650°C also reach 683.5MPa and 494.5MPa respectively, and the creep resistance of the alloy in service at 650°C is excellent, and the optimal creep strain and steady-state creep rate after creeping for 100h at 650°C and 100MPa are 0.43% and 7.23×10 -7 s -1 Therefore, the application of the rare earth microalloyed high-temperature titanium alloy material described in the present invention under high temperature conditions has broad prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate one or more embodiments of the present specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one or more embodiments of the present specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 is a metallographic microstructure diagram of the rare earth high temperature titanium alloy material after heat treatment according to Example 1 of the present invention;

[0023] Figure 2 is a metallographic microstructure diagram of the rare earth high temperature titanium alloy material after heat treatment according to Example 2 of the present invention;

[0024] Figure 3 This is a metallographic microstructure diagram of the rare earth high temperature titanium alloy material after heat treatment described in the comparative example.

[0025] Figure 4 It is a schematic flow chart of the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment according to the present invention. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments.

[0027] See also Figure 1-Figure 4 The embodiment of the present invention provides a method for improving the performance of rare earth high temperature titanium alloy by cryogenic treatment, comprising the following steps:

[0028] S1, subjecting the near-α rare earth high-temperature titanium alloy containing Si element to liquid nitrogen deep cryogenic treatment at the β phase transition point;

[0029] S2, after the cryogenic treatment, the β phase is retained to room temperature;

[0030] S3, further heating to achieve β-phase decomposition.

[0031] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the β phase transition point in step S1 is 990°C.

[0032] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the liquid nitrogen used for cryogenic treatment in step S1 is -196°C.

[0033] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the time of the cryogenic treatment in step S1 is 1-3 hours.

[0034] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the titanium alloy sample after the cryogenic treatment in step 1 is taken out, cooled to room temperature, and dried.

[0035] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, in step S3, the temperature is raised to 650° C. to 750° C. to perform β-phase decomposition.

[0036] According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment proposed in an embodiment of the present invention, the aging time for decomposing the β phase in step S3 is 1-4 hours.

[0037] The method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment according to an embodiment of the present invention also includes step: S4, air cooling, controlling the degree of decomposition of the β phase in the alloy, and then accurately controlling the content of nano-scale precipitated silicide in the alloy.

[0038] Example 1

[0039] Ti-6.5Al-2.5Sn-9Zr-0.5Mo-1.0Nb-1.0W-0.25Si series titanium alloy at 990℃ / 1h / liquid nitrogen cooling +-196℃ / 3h / air cooling +700℃ / 4h / air cooling, 990℃ / 1h / liquid nitrogen cooling +-196℃ / 3h / air cooling +650℃ / 4h / air cooling, 990℃ / 1h / liquid nitrogen cooling +-196℃ / 3h / air cooling +700℃ / 1h / air cooling, 990℃ / 1h / liquid nitrogen cooling +-196℃ / 3h / air cooling +700℃ / 4h / air cooling;

[0040] The microstructure of the alloy heat treated in step 1 was observed and its high temperature creep resistance was tested.

[0041] The microstructure observation results after heat treatment of the alloy show that: after 990℃ / 1h / liquid nitrogen cooling +-196℃ / 3h / air cooling treatment, large-sized silicides are basically dissolved (see Figure 1 ); after the alloy was aged at 700℃ / 4h / air cooling, 650℃ / 4h / air cooling, 700℃ / 1h / air cooling and 650℃ / 1h / air cooling, nano-scale dispersed silicide precipitation was observed. The number and size of the silicide precipitates were different. The size of the silicides gradually decreased with the decrease of heat treatment temperature from 750℃ to 650℃ and the reduction of aging time.

[0042] After the alloy was creep-treated at 650℃ / 100MPa / 100h, the creep strains of the alloy aged at 700℃ / 4h / air cooling, 650℃ / 4h / air cooling, 700℃ / 1h / air cooling and 650℃ / 1h / air cooling were 0.43%, 0.44%, 0.63% and 0.71%, respectively.

[0043] Example 2

[0044] Ti-6.5Al-2.5Sn-9Zr-0.5Mo-1.0Nb-1.0W-0.25Si series titanium alloy at 990℃ / 1h / liquid nitrogen cooling +-196℃ / 1h / air cooling +700℃ / 4h / air cooling, 990℃ / 1h / liquid nitrogen cooling +-196℃ / 1h / air cooling +650℃ / 4h / air cooling, 990℃ / 1h / liquid nitrogen cooling +-196℃ / 1h / air cooling +700℃ / 1h / air cooling, 990℃ / 1h / liquid nitrogen cooling +-196℃ / 1h / air cooling +700℃ / 1h / air cooling;

[0045] The microstructure of the alloy heat treated in step 1 was observed and its high temperature creep resistance was tested.

[0046] The microstructure observation results after heat treatment of the alloy show that: after 990℃ / 1h / liquid nitrogen cooling +-196℃ / 1h / air cooling, a small amount of large-sized silicides remain (see Figure 2 ); after the alloy was aged at 700℃ / 4h / air cooling, 650℃ / 4h / air cooling, 700℃ / 1h / air cooling and 650℃ / 1h / air cooling, nano-scale dispersed silicide precipitation was observed. The number and size of the silicide precipitates were different. The size of the silicides gradually decreased with the decrease of heat treatment temperature from 750℃ to 650℃ and the reduction of aging time.

[0047] After the alloy was creep-treated at 650℃ / 100MPa / 100h, the creep strains of the alloy aged at 700℃ / 4h / air cooling, 650℃ / 4h / air cooling, 700℃ / 1h / air cooling and 650℃ / 1h / air cooling were 0.52%, 0.38%, 0.53% and 0.47%, respectively.

[0048] Comparative Example 1

[0049] A large amount of large-sized silicides remain in Ti-6.5Al-2.5Sn-9Zr-0.5Mo-1.0Nb-1.0W-0.25Si titanium alloy after 990℃ / 1h / air cooling (see Figure 3 ); the alloy was then cooled at 700℃ / 4h / air-cooling, 650℃ / 4h / air-cooling, 700℃ / 1h / air-cooling and 650℃ / 1h / air-cooling; the size growth of silicide was more intense.

[0050] After the alloy was creep-treated at 650℃ / 100MPa / 100h, the creep strains of the alloy aged at 700℃ / 4h / air cooling, 650℃ / 4h / air cooling, 700℃ / 1h / air cooling and 650℃ / 1h / air cooling were 1.02%, 1.18%, 1.23% and 1.34%, respectively.

[0051] One or more embodiments of this specification are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this specification should be included in the scope of protection of this disclosure.

Claims

1. A method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment, characterized in that: The following steps are involved: S1, subjecting the near-α rare earth high-temperature titanium alloy containing Si element to liquid nitrogen deep cryogenic treatment at the β phase transition point; S2, after the cryogenic treatment, the β phase is retained to room temperature; S3, further heating to achieve β-phase decomposition.

2. The method for improving the performance of rare earth high temperature titanium alloy by cryogenic treatment according to claim 1, characterized in that: The β phase transition point in step S1 is 990°C.

3. The method for improving the performance of rare earth high temperature titanium alloy by cryogenic treatment according to claim 1, characterized in that: The liquid nitrogen used for cryogenic treatment in step S1 is at -196°C.

4. The method for improving the performance of rare earth high temperature titanium alloy by cryogenic treatment according to claim 1, characterized in that: The time of deep cooling treatment in step S1 is 1-3 hours.

5. According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment in claim 1, the titanium alloy sample after the cryogenic treatment in step 1 is taken out, cooled to room temperature, and dried.

6. According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment as claimed in claim 1, in step S3, the temperature is raised to 650°C to 750°C for β-phase decomposition.

7. According to the method for improving the performance of rare earth high-temperature titanium alloy by cryogenic treatment according to claim 1, the aging time for decomposition of the β phase in step S3 is 1-4 hours.

8. The method for improving the performance of rare earth high temperature titanium alloy by cryogenic treatment according to claim 1, characterized in that: Also includes the steps: S4, air cooling, controls the degree of β-phase decomposition in the alloy, and thus precisely controls the content of nano-scale silicide precipitation in the alloy.

Images