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CN-121992249-A - Superplastic titanium alloy and forming process thereof

CN121992249ACN 121992249 ACN121992249 ACN 121992249ACN-121992249-A

Abstract

The invention belongs to the technical field of titanium alloy, and particularly relates to a superplastic titanium alloy and a forming process thereof. The alloy comprises, by mass, 4.0-6.0% of Al, 3.0-4.5% of V, 0.05-0.30% of Sc, 0.5-1.2% of Fe, 0.08-0.16% of O, and the balance of titanium and unavoidable impurities, wherein the total content is 100%. According to the invention, sc element is introduced into the alloy, and the multi-step composite process of ageing treatment, low-temperature high-speed preforming and high-temperature low-speed precise forming is matched, so that the window of superplastic deformation moves to low temperature, and excellent superplastic performance is obtained.

Inventors

  • ZHU FENG
  • GUO YANING

Assignees

  • 宝鸡嘉琦金属有限公司

Dates

Publication Date
20260508
Application Date
20260302

Claims (10)

  1. 1. The superplastic titanium alloy is characterized by comprising the following chemical components in percentage by mass: 4.0 to 6.0 percent of Al, 3.0 to 4.5 percent of V, 0.05 to 0.30 percent of Sc, 0.5 to 1.2 percent of Fe, 0.08 to 0.16 percent of O, and the balance of titanium and unavoidable impurities, wherein the total is 100 percent; When the titanium alloy is subjected to superplastic forming, smelting each element, obtaining a fine-grain blank through thermomechanical treatment, ageing the fine-grain blank at 550-650 ℃ to enable Sc atoms to be biased in crystal boundaries and phase boundaries, pre-forming the blank after ageing at 610-630 ℃ and at a strain rate of 5X 10 -3 s -1 ~1×10 -2 s -1 , and then accurately forming at 700-750 ℃ and at a strain rate of 1X 10 -4 s -1 ~ 5×10 -4 s -1 , and carrying out annealing treatment.
  2. 2. The superplastic titanium alloy of claim 1, wherein the titanium alloy has a microstructure of α+β structure with an average grain size d of 2.0 μm or less and Sc-rich nanoclusters dispersed at the interface between the α and β phases.
  3. 3. A process for forming a superplastic titanium alloy according to claim 1, comprising the steps of: after smelting each element, obtaining a fine-grain blank through thermomechanical treatment; Aging the fine-grain blank at 550-650 ℃ to enable Sc atoms to be biased in crystal boundaries and phase boundaries; performing two-step superplastic forming on the blank subjected to aging treatment: Firstly, performing preliminary forming at 610-630 ℃ and at a strain rate of 5X 10 -3 s -1 ~1×10 -2 s -1 so that the material is deformed by 20-50%; The second step, under the condition of no unloading, the temperature is increased to 700-750 ℃, the strain rate is reduced to 1X 10 -4 s -1 ~ 5×10 -4 s -1 , the final forming pressure is applied, and the final accurate forming of the component is completed; And then annealing.
  4. 4. A forming process according to claim 3, wherein the time for the ageing treatment is 2 to 8 hours.
  5. 5. A forming process according to claim 3, wherein the two-step superplastic forming is carried out on an air pressure forming machine, the first step forming pressure being 1.0mpa to 2.0mpa, and the second step forming pressure being 2.5mpa to 5.0mpa.
  6. 6. A forming process according to claim 3, wherein the annealing treatment is carried out at a temperature of 550 ℃ to 600 ℃.
  7. 7. A forming process according to claim 3, characterized in that after melting each element, a fine-grained ingot is obtained by thermomechanical treatment, comprising in particular the following steps: proportioning according to the component proportion of titanium alloy, namely 4.0% -6.0% of Al, 3.0% -4.5% of V, 0.05% -0.30% of Sc, 0.5% -1.2% of Fe, 0.08% -0.16% of O, and the balance of titanium and unavoidable impurities, wherein the total is 100%, and smelting for multiple times by adopting a vacuum consumable arc furnace to ensure uniform components and obtain cast ingots; preserving the heat of the cast ingot at 1000-1020 ℃, carrying out homogenization treatment, and then carrying out furnace cooling; Heating the homogenized cast ingot to 980-1000 ℃ for heat preservation, then performing multi-pass forging, controlling the total deformation to 60-80%, and performing furnace return heat preservation between passes to recover the temperature; and cooling the forged blank to 750-800 ℃, preserving heat, carrying out multi-pass hot rolling, controlling the total deformation to 70-90%, and controlling the final rolling temperature to be not lower than 750 ℃.
  8. 8. The molding process of claim 7, wherein the homogenization treatment is performed for a hold time of 8 to 24 hours.
  9. 9. The forming process according to claim 7, wherein the heat is preserved for 1-2 hours at 980 ℃ to 1000 ℃.
  10. 10. The forming process according to claim 7, wherein the heat is preserved for 0.5 to 1 hour at 750 ℃ to 800 ℃.

Description

Superplastic titanium alloy and forming process thereof Technical Field The invention belongs to the technical field of titanium alloy, and particularly relates to a superplastic titanium alloy and a forming process thereof. Background Titanium alloys are widely used in the fields of aerospace, biomedical and high-end equipment manufacturing due to their high specific strength, excellent corrosion resistance and biocompatibility. However, titanium alloys have insufficient plastic properties, resulting in poor formability. Superplastic forming technology provides an effective way for solving the difficult problem. At present, titanium alloy superplastic forming is generally carried out by smelting, thermo-mechanical treatment (such as multipass rolling, extrusion or forging) to obtain fine equiaxed crystal structure. And then loading and forming the pretreated titanium alloy material under the conditions of high temperature and low strain rate, wherein in the process, the material mainly depends on a grain boundary sliding mechanism to realize uniform large deformation. Superplasticity refers to the phenomenon that a material exhibits an abnormally high elongation without necking under the above-mentioned high temperature and strain rate conditions. However, in the conventional superplastic titanium alloy, there are problems in that the temperature is high and the superplastic deformation elongation is not large enough in realizing the above-mentioned large deformation process. For example, the superplastic deformation temperature of Ti-6Al-4V is higher than 900 ℃, and the maximum elongation is about 900%. Along with the continuous expansion of the application field of the titanium alloy, the requirements on the superplastic property of the titanium alloy are continuously improved, and the problem that how to enable the titanium alloy to have larger superplastic deformation elongation at lower temperature is needed to be solved. Disclosure of Invention In order to solve the technical problems, the invention provides a superplastic titanium alloy and a forming process thereof, wherein the titanium alloy has excellent superplastic deformation elongation at relatively low temperature by improving alloy components and the forming process. According to the invention, sc element is introduced into the titanium alloy component to form Sc-rich nanoclusters with high thermal stability, so that the transformation temperature of beta phase can be reduced, and the recrystallization temperature of alpha phase can be increased, thereby enabling the window of superplastic deformation to move to low temperature. And during plastic deformation, aging treatment is carried out on the fine-grain blank, and then low-temperature high-speed preforming and high-temperature low-speed precise forming are carried out, so that the material obtains large high superplastic deformation elongation. The invention is realized by the following technical scheme. The first object of the invention is to provide a superplastic titanium alloy which comprises the following chemical components in percentage by mass: 4.0 to 6.0 percent of Al, 3.0 to 4.5 percent of V, 0.05 to 0.30 percent of Sc, 0.5 to 1.2 percent of Fe, 0.08 to 0.16 percent of O, and the balance of titanium and unavoidable impurities, wherein the total is 100 percent. When the titanium alloy is subjected to superplastic forming, smelting each element, obtaining a fine-grain blank through thermomechanical treatment, ageing the fine-grain blank at 550-650 ℃ to enable Sc atoms to be biased in crystal boundaries and phase boundaries, pre-forming the blank after ageing at 610-630 ℃ and at a strain rate of 5X 10 -3s-1~1×10-2s-1, and then accurately forming at 700-750 ℃ and at a strain rate of 1X 10 -4s-1~ 5×10-4s-1, and carrying out annealing treatment. In a preferred embodiment of the invention, sc is 0.10% -0.25%. According to the invention, sc element is introduced into the titanium alloy component, sc atoms are preferentially biased to grain boundaries and phase boundaries during intermediate heat treatment, sc-rich nanoclusters with high heat stability are formed, and a window subjected to superplastic deformation is moved to a low temperature. In a preferred embodiment of the invention, the microstructure of the titanium alloy is an ultra-fine grain dual-phase (α+β) structure with an average grain size d of 2.0 μm or less and with dispersed Sc-rich nanoclusters at the interface of the α and β phases. The second object of the present invention is to provide a forming process of the above superplastic titanium alloy, comprising the steps of: After each element is melted, a fine-grain ingot is obtained by thermo-mechanical treatment. Aging the fine-grain blank at 550-650 ℃ to enable Sc atoms to be biased at crystal boundaries and phase boundaries. The blank after aging treatment is subjected to two-step superplastic forming, namely, the blank is preformed at 610-630 ℃ and at 5 multiplie