Preparation method of titanium alloy slow-cooling microstructure

Abstract

The invention discloses a preparation method of a titanium alloy slow-cooling microstructure, which comprises the following steps: (1) heating: heating a double-phase titanium alloy, and preserving heat after heating, the heating temperature meets the condition that T-Tc is more than or equal to 0 DEG C and less than or equal to 60 DEG C, T is the heating temperature, and Tc is the beta / alpha transformation temperature of the double-phase titanium alloy; (2) slow cooling: preparing a titanium alloy slow cooling microstructure after slow cooling, wherein the slow cooling rate is 1-5 DEG C / min; the prepared slow-cooling microstructure of the titanium alloy is a polygonal microstructure, a short rod-shaped microstructure or a transition microstructure from a polygon to a short rod. Compared with the prior art, the titanium alloy slow-cooling microstructure prepared through the method is high in plasticity and toughness.

Description

Technical Field

[0001] The invention relates to the field of titanium alloy materials, and in particular to a method for preparing a titanium alloy slow cooling microstructure. Background Art

[0002] Titanium alloy materials have the advantages of high specific strength, long-lasting corrosion resistance, and low resistance to thermal deformation. (α+β) dual-phase titanium alloys have a variety of microstructures because they have two phase structures, α and β. Typical titanium alloy materials, such as Ti6Al4V (TC4), can usually obtain lamellar structures or basketweave structures with different microscopic characteristics by annealing in the β zone and combining different cooling rates; they can also obtain dual-state structures with different phase ratios and phase sizes by annealing in the near β zone and the (α+β) two-phase zone. These microstructures are as follows: Figure 1 As shown: lamellar structure (b) and basketweave structure are usually known for their high fracture toughness and fatigue performance, equiaxed structure (a) and bimodal structure (c) are often outstanding for their good plasticity and strength-plasticity matching performance.

[0003] The patents in the field of titanium alloy material research in my country are mostly concentrated in the aspects of alloy smelting, alloy design, plate and bar deformation material preparation, titanium parts near net shape process method, etc. However, the engineering application of titanium alloy materials will involve problems such as plate and bar deformation material forming processability, parts product welding processability, near net shape processability, etc. The alloy materials that have been widely used in the fields of aerospace, shipbuilding and chemical engineering at home and abroad are still typical alloys developed by developed countries such as Europe, America, Russia and Japan, such as TC4, TC6, TC11, TC18, TA1, TA15, TB7, TB8, etc. At present, there are few reports on the performance potential of the above-mentioned typical alloys, only the heat treatment process method of three-state organization (CN101717904A, CN103938139A), multi-level organization refinement process (CN 104745995A), raft-like primary phase dual-state organization heat treatment method (CN101429637A), equiaxed grain refinement process (CN1032962A), etc., but none of them can obtain good plasticity. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a slow-cooling microstructure of a titanium alloy in view of the above-mentioned technical status quo. The slow-cooling microstructure of the titanium alloy prepared by the method has good plasticity.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for preparing a slow-cooling microstructure of a titanium alloy, characterized in that it comprises the following steps:

[0006] ① Heating: heating the duplex titanium alloy, and then keeping the temperature, wherein the heating temperature satisfies 0°C≤T-Tc≤60°C, wherein T is the heating temperature, and Tc is the β / α transformation temperature of the duplex titanium alloy;

[0007] ② Slow cooling: After slow cooling, a slow cooling microstructure of the titanium alloy is obtained, and the slow cooling rate is: 1°C to 5°C / min;

[0008] The obtained slow-cooled titanium alloy microstructure is a polygonal structure, a short rod-shaped structure or a transitional structure from a polygonal structure to a short rod-shaped structure.

[0009] Generally, a polygonal structure can be obtained when the slow cooling rate is 1°C / min; a short rod-shaped structure can be obtained when the slow cooling rate is 5°C / min; and a transitional structure from polygonal to short rod-shaped can be obtained when the slow cooling rate is between the above boundary cooling rates.

[0010] Preferably, the duplex titanium alloy is a TC series alloy.

[0011] Preferably, the aspect ratio of the short rod-shaped tissue is 3-5.

[0012] In order to improve the plasticity and toughness of the slow-cooled microstructure of the titanium alloy obtained, preferably, the holding time of step ① is 0.4-0.6h. The holding time makes the structure of the whole sample more uniform, the grains are refined, and the internal stress is released, thereby improving the plasticity and toughness of the slow-cooled microstructure of the titanium alloy obtained.

[0013] Preferably, the heating temperature of step ① satisfies 0°C≤T-Tc≤50°C.

[0014] Preferably, the heating method in step ① is heating with the furnace or heating into the furnace when the temperature reaches the temperature.

[0015] Preferably, the obtained titanium alloy slow-cooling microstructure has a tensile strength of ≥900 MPa and an elongation of ≥10% under quasi-static tensile conditions at room temperature.

[0016] Compared with the prior art, the advantages of the present invention are: by controlling the slow cooling rate, the slow cooling microstructure of the obtained titanium alloy is a polygonal structure, a short rod-shaped structure or a transitional structure from a polygon to a short rod-shaped structure. These microstructures are new microstructures, all of which have good strength-plasticity matching characteristics and have certain engineering application value; the preparation method is heating and slow cooling, the preparation method is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the microstructure of titanium alloy in the prior art;

[0018] Figure 2 Schematic diagram of the microstructure of the titanium alloy of Example 1;

[0019] Figure 3 Schematic diagram of the microstructure of the titanium alloy of Example 3;

[0020] Figure 4 Schematic diagram of the microstructure morphology of the titanium alloy of Comparative Example 1. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings.

[0022] Example 1

[0023] A method for preparing a slow-cooled titanium alloy microstructure comprises the following steps:

[0024] ① Heating: The duplex titanium alloy uses cubic TC4, the sample size is 50mm×50mm×50mm, and the β / α transformation temperature is 1050°C; the duplex titanium alloy is heated to 1050°C in a furnace and then kept warm for 0.5h.

[0025] ② Slow cooling: After slow cooling, the slow cooling microstructure of titanium alloy is obtained, and the slow cooling rate is 5℃ / min;

[0026] like Figure 2 As shown, the slow-cooled microstructure of the titanium alloy obtained in this embodiment is a short rod-shaped structure with an aspect ratio of about 3.62.

[0027] Example 2

[0028] A method for preparing a slow-cooled titanium alloy microstructure comprises the following steps:

[0029] ① Heating: The duplex titanium alloy uses cubic TC4, the sample size is 50mm×50mm×50mm, and the β / α transformation temperature is 1050°C; the duplex titanium alloy is heated to 1050°C in a furnace and then kept warm for 0.5h.

[0030] ② Slow cooling: After slow cooling, the slow cooling microstructure of titanium alloy is obtained, and the slow cooling rate is 3℃ / min;

[0031] The slow-cooled titanium alloy microstructure obtained in this embodiment is a compressed short rod structure, that is, a transitional structure from polygonal to short rod, with an aspect ratio of about 2.14.

[0032] Example 3

[0033] A method for preparing a slow-cooled titanium alloy microstructure comprises the following steps:

[0034] ① Heating: The duplex titanium alloy uses cubic TC4, the sample size is 50mm×50mm×50mm, and the β / α transformation temperature is 1050°C; the duplex titanium alloy is heated to 1050°C in a furnace and then kept warm for 0.5h.

[0035] ② Slow cooling: After slow cooling, the slow cooling microstructure of titanium alloy is obtained, and the slow cooling rate is 1℃ / min;

[0036] like Figure 3 As shown, the slow-cooled microstructure of the titanium alloy obtained in this embodiment is a polygonal structure with a relatively small aspect ratio, and the aspect ratio is about 1.37.

[0037] Comparative Example 1

[0038] The following steps are involved:

[0039] ① Heating: The duplex titanium alloy uses cubic TC4, the sample size is 50mm×50mm×50mm, and the β / α transformation temperature is 1050°C; the duplex titanium alloy is heated to 1050°C in a furnace and then kept warm for 0.5h.

[0040] ② Slow cooling: After slow cooling, the slow cooling microstructure of titanium alloy is obtained, and the slow cooling rate is 10℃ / min;

[0041] like Figure 4 As shown, the slow-cooled microstructure of the titanium alloy obtained in this embodiment is a lamellar structure.

[0042] Table 1 Room temperature quasi-static tensile properties of slow cooling microstructures of titanium alloys in Examples 1-3 and Comparative Example 1

[0043] Tensile strength / MPa Yield strength / MPa Elongation / % Sectional shrinkage / % Example 1 945 905 11 25 Example 2 960 912 13 29 Example 3 954 910 18 33 Comparative Example 1 927 896 9 21

[0044] It can be seen from the embodiments and comparative examples that the tensile strength of embodiments 1-3 is ≥900MPa, the yield strength is ≥900MPa; the elongation is ≥10%, and the cross-sectional shrinkage is ≥25%, which are all higher than those of comparative example 1; it can be seen that the polygonal structure, short rod-shaped structure or polygonal to short rod-shaped transition structure obtained by the method of the embodiment has good plasticity and toughness compared with the lamellar structure; and as the slow cooling rate decreases, the aspect ratio of the prepared microstructure decreases and becomes polygonal, and this change does not significantly affect the strength of the alloy but improves the plasticity of the alloy.

Claims

1. A method for preparing a slow-cooled titanium alloy microstructure, characterized in that: The following steps are involved: ① Heating: heating the duplex titanium alloy, and then keeping the temperature, the heating temperature satisfies 0°C≤T-Tc≤60°C, T is the heating temperature, and Tc is the β / α transformation temperature of the duplex titanium alloy; ② Slow cooling: After slow cooling, a slow cooling microstructure of the titanium alloy is obtained, and the slow cooling rate is: 1°C to 5°C / min; The obtained slow-cooled titanium alloy microstructure is a polygonal structure, a short rod-shaped structure or a transitional structure from a polygonal structure to a short rod-shaped structure.

2. The method for preparing a titanium alloy slow cooling microstructure according to claim 1, characterized in that: The duplex titanium alloy is a TC series alloy.

3. The method for preparing a titanium alloy slow cooling microstructure according to claim 1, characterized in that: The aspect ratio of the short rod-shaped structure is 3-5.

4. The method for preparing a titanium alloy slow cooling microstructure according to claim 1, characterized in that: The insulation time of step ① is 0.4-0.6h.

5. The method for preparing a titanium alloy slow cooling microstructure according to claim 1, characterized in that: The heating temperature of step ① satisfies 0°C≤T-Tc≤50°C.

6. The method for preparing a titanium alloy slow cooling microstructure according to any one of claims 1 to 5, characterized in that: The heating method of step ① is heating with the furnace or heating into the furnace when the temperature reaches the temperature.

7. The method for preparing a titanium alloy slow cooling microstructure according to any one of claims 1 to 5, characterized in that: The obtained titanium alloy slow cooling microstructure has a tensile strength of ≥900MPa and an elongation of ≥10% under quasi-static tensile conditions at room temperature.

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