Method for controlling strength and toughness of duplex titanium alloy

Abstract

The application discloses a method for controlling the strength and toughness of a duplex structure titanium alloy, and the titanium alloy blank is subjected to multi-fire upsetting deformation, the initial upsetting temperature is not higher than 110 DEG C above the phase transition point, the final upsetting temperature is not lower than 100 DEG C below the phase transition point, the intermediate blank after forging is heated to 750-780 DEG C for ordinary annealing, and after annealing, air cooling is carried out to room temperature, the annealed blank is heated to 50 DEG C below the phase transition temperature, and after a certain period of heat preservation, radial precision forging is carried out to form a rod. The application adopts the combined mode of multi-pass large deformation forging and radial forging forming, and prepares the titanium alloy rod with the microscale and micro-nanoscale mixed crystal structure, so that the strength of the titanium alloy is increased and the plasticity is not reduced.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy technology and relates to a method for controlling the strengthening and toughening properties of dual-phase titanium alloys. Background Technology

[0002] Future high-end equipment, such as marine and aerospace equipment, urgently requires lightweight alloy materials that possess both high strength and high toughness. While there is a relentless pursuit of a balance between strength and ductility in metallic materials, these two properties are contradictory: increased strength is accompanied by decreased toughness and ductility, a phenomenon that traditional strengthening techniques struggle to reverse. Titanium alloys, as the most promising equipment material, also require addressing or mitigating this issue. Therefore, improving their strength and ductility is a crucial problem that urgently needs to be solved in the selection of materials for equipment.

[0003] Currently, methods to improve the strength and ductility of duplex titanium alloys mainly include composition design and microstructure control. In terms of composition design, alloying elements can activate non-basal plane slip, improving ductility but reducing strength. Microstructure control includes deformation refinement and heat treatment to regulate phase composition, content, and morphology. Grain refinement increases grain boundaries, hindering dislocation slip and significantly improving strength, but dislocation storage and work hardening reduce ductility. Heat treatment can improve the strength-ductility balance by adjusting the content and morphology of primary and secondary α phases in the microstructure, but it has limitations in improving performance.

[0004] Therefore, improving the strength and ductility of duplex titanium alloys and achieving an optimal strength-ductility balance is the main technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the strengthening and toughening properties of dual-phase titanium alloys, which solves the problem of mismatch between strength and plasticity in existing titanium alloys.

[0006] The technical solution adopted in this invention is a method for controlling the strengthening and toughening properties of dual-phase titanium alloys, comprising the following steps:

[0007] Step 1: The titanium alloy billet is subjected to multiple forging and drawing deformations. For each forging and drawing deformation, the initial forging temperature is not higher than 110°C above the phase transformation point, and the final forging temperature is not lower than 100°C below the phase transformation point.

[0008] Step 2: Heat the intermediate billet after forging in Step 1 to 750-780℃ for ordinary annealing, and then air cool to room temperature after annealing.

[0009] Step 3: Heat the annealed billet to 50°C below the phase transformation temperature, hold it at that temperature for a period of time, and then radially precision forge it into a bar.

[0010] In step 1, the titanium alloy billet is subjected to five upsetting and drawing deformation processes.

[0011] In step 1, the first heating and drawing deformation includes heating the titanium alloy billet to 90-110°C above the phase transformation point and holding it at that temperature for 2-4 hours, then heating and drawing the billet for the first heating and grinding.

[0012] In step 1, the second forging deformation includes heating the first forging billet to 50-70°C above the phase transformation point, holding it at that temperature for 30-60 minutes, performing the second forging, and grinding.

[0013] In step 1, the third forging deformation includes heating the second forging billet to 20-40°C above the phase transformation point, holding it at that temperature for 30-60 minutes, and then performing the third forging and grinding.

[0014] In step 1, the fourth forging deformation includes heating the third forging billet to the phase transformation temperature ±10℃ and holding it at that temperature for 30min-60min, then performing the fourth forging and grinding.

[0015] In step 1, the fifth forging deformation includes heating the fourth forging billet to 30-40°C below the phase transformation temperature, holding it at that temperature for 30-60 minutes, performing the fifth forging, grinding, and forming an intermediate billet.

[0016] In step 2, the intermediate billet forged in step 1 is heated to 750-780℃ and held for 1-3 hours for ordinary annealing.

[0017] In step 3, the annealed billet is heated to 50°C below the phase transformation temperature and held for 1-3 hours. After holding, it is radially precision forged into a bar. The radial precision forging section shrinkage rate is not less than 60%.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) By combining multi-pass large deformation forging and radial forging, titanium alloy bars with micron-scale and micro-nano-scale mixed crystal structure are prepared, so as to achieve the effect of increasing the strength of titanium alloy without reducing its plasticity.

[0020] (2) A near-equiaxed microstructure with uniform and fine structure is prepared by multi-pass large deformation forging, and then annealing can stabilize the microstructure uniformity and eliminate the work hardening and internal stress generated during the material deformation process.

[0021] (3) By using radial forging, the grains can be further refined, causing the α phase at the grain boundary to deform and elongate, and the α phase within the broken grain to break and fracture, thus preparing a mixed crystal structure with micron and micro-nano scales. When subjected to load, the micron-scale grains bear the strain first and deform first, while the micro-nano-scale grains have high yield strength and deform later. The strain gradient formed between the two structures accumulates dislocations, thereby playing a deformation-induced strengthening role and achieving the effect of increasing strength without reducing plasticity. Attached Figure Description

[0022] Figure 1 This is a 200x magnified metallographic image of the axial microstructure of the titanium alloy bar prepared in Example 1 of this invention;

[0023] Figure 2 This is a 500x magnified metallographic image of the axial microstructure of the titanium alloy bar prepared in Example 1 of this invention;

[0024] Figure 3 This is a metallographic image of the radial microstructure of the titanium alloy bar prepared in Example 1 of this invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] A method for controlling the strengthening and toughening properties of dual-phase titanium alloys includes the following steps:

[0028] Step 1: The TC4 titanium alloy billet with a phase transformation temperature of 980℃ is subjected to five upsetting and drawing deformation processes. The specific process is as follows:

[0029] Step 1.1, the first heat-drawing deformation includes heating the TC4 titanium alloy billet to 1090℃, holding it at that temperature for 2 hours, performing the first heat-drawing, air cooling, and then grinding to obtain billet 1-1.

[0030] Step 1.2, the second forging deformation includes heating the first forging billet to 1050℃, holding it at that temperature for 60 minutes, performing the second forging, air cooling, and then grinding to obtain billet 1-2.

[0031] Step 1.3, the third forging deformation, includes heating the second forging billet to 1020℃, holding it at that temperature for 40 minutes, performing the third forging, air cooling and grinding to obtain billet 1-3.

[0032] Step 1.4, the fourth forging deformation, includes heating the third forging billet to 990℃ and holding it for 60 minutes, performing the fourth forging, air cooling and grinding to obtain billet 1-4.

[0033] Step 1.5, the fifth forging deformation, includes heating the fourth forging billet to 945°C below the phase transformation temperature, holding it at that temperature for 60 minutes, performing the fifth forging, grinding, and forming an intermediate billet.

[0034] Step 2: Heat the intermediate billet forged in Step 1 to 780℃, hold for 3 hours, and air cool to room temperature;

[0035] Step 3: Heat the annealed billet to 930℃ and hold for 2 hours. After holding, radially finish forge it into a bar. The radial finish forging section has a reduction of area of ​​70%.

[0036] The metallographic structure of the titanium alloy bar prepared in Example 1 was observed as follows: Figure 1-3 As shown in the metallographic image, the titanium alloy rod prepared by the dual-phase titanium alloy strengthening and toughening performance control method of the present invention has fine internal grains and a mixed crystal structure with micron and micro-nano scales.

[0037] The mechanical properties of the titanium alloy bar prepared in Example 1 were tested. The tensile strength was 1026 MPa, the yield strength was 927 MPa, the elongation was 15.5%, and the reduction of area was 61%.

[0038] Example 2

[0039] A method for controlling the strengthening and toughening properties of dual-phase titanium alloys includes the following steps:

[0040] Step 1: The TC4 titanium alloy billet with a phase transformation temperature of 980℃ is subjected to five upsetting and drawing deformation processes. The specific process is as follows:

[0041] Step 1.1, the first heat-drawing deformation includes heating the TC4 titanium alloy billet to 1070℃, holding it at that temperature for 3 hours, performing the first heat-drawing, air cooling, and then grinding to obtain billet 2-1.

[0042] Step 1.2, the second forging deformation includes heating the first forging billet to 1030℃, holding it at that temperature for 50 minutes, performing the second forging, air cooling, and then grinding to obtain billet 2-2.

[0043] Step 1.3, the third forging deformation, includes heating the second forging billet to 1000℃, holding it at that temperature for 50 minutes, performing the third forging, air cooling and grinding to obtain billet 2-3.

[0044] Step 1.4, the fourth forging deformation, includes heating the third forging billet to 970℃ and holding it for 50 minutes, performing the fourth forging, air cooling and grinding to obtain billet 2-4.

[0045] Step 1.5, the fifth forging deformation, includes heating the fourth forging billet to 940°C below the phase transformation temperature, holding it at that temperature for 50 minutes, performing the fifth forging, grinding, and forming an intermediate billet.

[0046] Step 2: Heat the intermediate billet forged in Step 1 to 750℃, hold for 1 hour, and air cool to room temperature;

[0047] Step 3: Heat the annealed billet to 930℃ and hold for 1 hour. After holding, radially finish forge it into a bar. The radial finish forging section has a reduction of area of ​​60%.

[0048] The mechanical properties of the titanium alloy bar prepared in Example 2 were tested. The tensile strength was 1049 MPa, the yield strength was 955 MPa, the elongation was 14.5%, and the reduction of area was 62%.

[0049] Example 3

[0050] A method for controlling the strengthening and toughening properties of dual-phase titanium alloys includes the following steps:

[0051] Step 1: The TC4 titanium alloy billet undergoes five upsetting and drawing deformation processes, as detailed below:

[0052] Step 1.1, the first heat-drawing deformation includes heating the TC4 titanium alloy billet to 1080℃, holding it at that temperature for 4 hours, performing the first heat-drawing, air cooling, and then grinding to obtain billet 3-1.

[0053] Step 1.2, the second forging deformation includes heating the first forging billet to 1040℃, holding it at that temperature for 30 minutes, performing the second forging, air cooling, and then grinding to obtain billet 3-2.

[0054] Step 1.3, the third forging deformation, includes heating the second forging billet to 1010℃, holding it at that temperature for 30 minutes, performing the third forging, air cooling, and then grinding to obtain billet 3-3.

[0055] Step 1.4, the fourth forging deformation, includes heating the third forging billet to 980℃ and holding it for 30 minutes, performing the fourth forging, air cooling and grinding to obtain billet 3-4.

[0056] Step 1.5, the fifth forging deformation, includes heating the fourth forging billet to 950°C below the phase transformation temperature, holding it at that temperature for 30 minutes, performing the fifth forging, grinding, and forming an intermediate billet.

[0057] Step 2: Heat the intermediate billet forged in Step 1 to 760℃, hold for 2 hours, and air cool to room temperature;

[0058] Step 3: Heat the annealed billet to 930℃ and hold for 2 hours. After holding, radially finish forge it into a bar. The radial finish forging section has a reduction of area of ​​75%.

[0059] The mechanical properties of the titanium alloy bar prepared in Example 3 were tested. The tensile strength was 1038 MPa, the yield strength was 946 MPa, the elongation was 15.5%, and the reduction of area was 61%.

Claims

1. A method for controlling the strengthening and toughening properties of dual-phase titanium alloys, characterized in that, Includes the following steps: Step 1: The titanium alloy billet is subjected to multiple forging and drawing deformations. For each forging and drawing deformation, the initial forging temperature is not higher than 110°C above the phase transformation point, and the final forging temperature is not lower than 100°C below the phase transformation point. In step 1, the titanium alloy billet undergoes five heating and drawing processes. The first heating and drawing process involves heating the titanium alloy billet to 90-110°C above the phase transformation point and holding it at that temperature for 2-4 hours, followed by heating and grinding. The second heating and drawing process involves heating the billet from the first heating process to 50-70°C above the phase transformation point and holding it at that temperature for 30-60 minutes, followed by heating and grinding. The third heating and drawing process involves heating the billet from the second heating process to... The third forging and grinding process involves heating the forged billet from the third forging process to 20-40℃ above the phase transformation temperature and holding it for 30-60 minutes. The fourth forging and grinding process involves heating the forged billet from the third forging process to ±10℃ above the phase transformation temperature and holding it for 30-60 minutes. The fifth forging and grinding process involves heating the forged billet from the fourth forging process to 30-40℃ below the phase transformation temperature and holding it for 30-60 minutes. The fifth forging and grinding process forms an intermediate billet. Step 2: Heat the intermediate billet after forging in Step 1 to 750-780℃ for ordinary annealing, and then air cool to room temperature after annealing. Step 3: Heat the annealed billet to 50°C below the phase transformation temperature, hold it at that temperature for a period of time, and then radially precision forge it into a bar.

2. The method for controlling the strengthening and toughening properties of duplex titanium alloys according to claim 1, characterized in that, In step 2, the intermediate billet forged in step 1 is heated to 750-780℃ and held at that temperature for 1-3 hours for ordinary annealing.

3. The method for controlling the strengthening and toughening properties of duplex titanium alloys according to claim 1, characterized in that, In step 3, the annealed billet is heated to 50°C below the phase transformation temperature and held for 1-3 hours. After holding, it is radially precision forged into a bar stock with a cross-sectional shrinkage rate of not less than 60%.

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