Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide an ultrahigh-strength heterostructure titanium alloy and a preparation method thereof, which can effectively improve the strong plasticity of the titanium alloy and have the advantages of simple components and short preparation process.
The technical scheme of the invention is as follows:
the invention relates to a titanium alloy with an ultrahigh-strength heterostructure, which comprises the following components in percentage by mass: 2.5-4% of Al, 4-6% of V, 5-8% of Mo, and the balance of Ti and other inevitable impurities.
The ultrahigh-strength heterostructure titanium alloy provided by the invention is a Ti-Al-V-Mo quaternary system, Al, V and Mo are selectively added as alloy elements in the composition, and compared with the existing solid solution strengthened titanium alloy, the ultrahigh-strength heterostructure titanium alloy avoids expensive alloy elements such as Zr, Cr and Ta, thereby reducing the cost of alloy raw materials.
The invention relates to an ultrahigh-strength heterostructure titanium alloy, wherein the microstructure of the alloy is composed of an (alpha + beta) dual-phase titanium matrix and beta single-phase titanium fibers, the volume fraction of the alpha phase in the (alpha + beta) dual-phase titanium matrix is 60-80%, the diameter of the beta single-phase titanium fibers is 10-50 mu m, and the fiber spacing is 50-100 mu m.
The invention relates to a preparation method of a titanium alloy with an ultrahigh-strength heterostructure, which comprises the following steps:
weighing Ti powder, AlV intermediate alloy powder and Mo powder according to designed alloy components, mixing to obtain mixed powder, performing compression molding on the mixed powder to obtain a pressed blank bar, sintering the pressed blank bar to obtain a sintered blank bar, performing hot rotary forging on the sintered blank bar to obtain a heterostructure titanium alloy bar, and performing stress relief annealing on the hot rotary forged titanium alloy bar to obtain an ultrahigh-strength heterostructure titanium alloy; the hot rotary swaging processing process comprises the steps of firstly carrying out single-phase region primary swaging and then carrying out double-phase region final swaging.
Preferably, the particle size of the Ti powder is 20-50 μm, the particle size of the AlV master alloy powder is 15-30 μm, and the particle size of the Mo powder is 1-5 μm.
The powder shapes of the Ti powder, the AlV intermediate alloy powder particles and the Mo powder can be nearly spherical or irregular particles.
Preferably, the mixing is performed in a three-dimensional mixer under the protection of argon atmosphere, and the mixing time is 5-10 hours. In the actual operation process, high-purity argon is adopted to fill the hopper.
Preferably, the compression molding mode is cold isostatic pressing, the pressure of the compression molding is 180-250 MPa, and the pressure maintaining time is 1-3 min.
Preferably, the sintering is carried out in a vacuum environment, the sintering temperature is 1100-1250 ℃, the heat preservation time is 1-2 hours, and the vacuum degree is lower than 1 x 10-3Pa。
Preferably, the temperature of the single-phase zone initial forging is 1000-1100 ℃, and the deformation of the initial section is 30-50%; the temperature of final forging of the two-phase region is 900-950 ℃, and the deformation amount of the final forging is 85-98%.
In the actual operation process, the final forging can be carried out in multiple passes, and the inter-pass furnace return is carried out for 5-10 min.
Preferably, the stress relief annealing temperature is 300-400 ℃, and the heat preservation time is 30-60 min. The cooling mode is furnace cooling.
Compared with the prior art, the invention has the following beneficial effects:
according to the ultrahigh-strength heterostructure titanium alloy provided by the invention, Al, V and Mo are selectively added as alloy elements, and compared with the existing solid solution strengthening type titanium alloy, expensive alloy elements such as Zr, Cr and Ta are avoided, so that the cost of alloy raw materials is reduced. In the microstructure, in the heterostructure titanium alloy, an (alpha + beta) dual-phase titanium matrix is formed by solid solution of Al and V elements, a beta single-phase region is formed by controlling the incomplete expansion of Mo element, and a beta single-phase fiber is formed by hot swaging. Compared with the existing titanium alloy with a homogeneous structure, the titanium alloy with a heterogeneous structure can generate a strain gradient during deformation, so that a remarkable back stress strengthening effect is obtained, the alloy strength reaches more than 1500MPa, the elongation is higher than 7%, and the synergistic promotion of the strong plasticity is realized.
In addition, the preparation method of the ultrahigh-strength heterostructure titanium alloy provided by the invention realizes the uniformity of components through a powder metallurgy process, and avoids the problems of component segregation and structural heterogeneity in the conventional ingot metallurgy process. Compared with the existing aging strengthening titanium alloy preparation process, the preparation process disclosed by the invention is short in process flow, and does not need long-time aging treatment, so that the material production efficiency and the equipment energy efficiency are improved.
Detailed Description
The present invention is described in further detail with reference to the following specific examples, but the scope of the present invention is not limited to the following specific examples, and all equivalent substitutions based on the examples of the present invention are within the scope of the present invention.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Example 1
The titanium alloy with the ultrahigh-strength heterostructure comprises the following elements in percentage by mass: 3% of Al, 4.5% of V, 5% of Mo, and the balance of Ti and other inevitable impurities. The preparation method comprises the following steps:
(1) weighing Ti powder (D) according to the above components5034 μm) and AlV master alloy powder (D)5027 μm) and Mo powder (D)502 μm), placing in a three-dimensional blender hopper, flushing high-purity argon as protective atmosphere, and uniformly mixing for 6h to obtain mixed powder.
(2) And (3) carrying out cold isostatic pressing on the mixed powder, controlling the pressure of the cold isostatic pressing to be 200MPa, and keeping the pressure for 2min to obtain a powder pressed billet.
(3) Vacuum sintering the powder pressed billet, controlling the sintering temperature to be 1200 ℃,the heat preservation time is 1.5h, and the vacuum degree is less than 5 multiplied by 10-3And Pa, cooling along with the furnace to obtain a titanium alloy sintered blank bar.
(4) Performing hot rotary forging on a titanium alloy sintered blank bar, firstly, preserving the temperature of the bar for 30min at 1000 ℃, and then performing primary forging, wherein the deformation of the primary forging is 44%; and then, preserving the temperature of the bar at 930 ℃ for 10min, and performing finish forging, wherein the finish forging deformation is 96%, so as to obtain the heterostructure titanium alloy bar.
(5) And (3) performing stress relief annealing on the hot-swaged titanium alloy bar, wherein the annealing temperature is 350 ℃, the heat preservation time is 30min, and cooling along with the furnace to obtain the ultrahigh-strength heterostructure titanium alloy.
The XRD diffraction result of the ultra-high strength heterostructure titanium alloy prepared in the embodiment is shown in figure 1, and the alloy consists of alpha titanium and beta titanium and has no other metastable phase. An SEM structure photograph of the alloy is shown in FIG. 2, and a macroscopic photograph shows that a large number of fiber structures exist in the alloy, the fiber diameter is 10-40 μm, and the fiber spacing is 50-80 μm; the high magnification photograph shows that the alloy consists of microstructure composed of (alpha + beta) two-phase titanium matrix and beta single-phase titanium fiber, and the volume fraction of alpha phase in the matrix is determined to be about 72%. The tensile property curve of the alloy is shown in figure 3, and the prepared heterostructure titanium alloy has the ultrahigh tensile strength of 1634MPa and keeps good elongation of 7%. The tensile fracture morphology is shown in fig. 4, a large number of fine dimples can be seen in the fracture, which indicates that the fracture mode of the ultrahigh-strength heterostructure titanium alloy is ductile fracture. Compared with the existing titanium alloy material, the ultrahigh-strength heterostructure titanium alloy obtained by the embodiment has better comprehensive mechanical properties.
Example 2
The titanium alloy with the ultrahigh-strength heterostructure comprises the following elements in percentage by mass: 4% of Al, 6% of V, 6% of Mo, and the balance of Ti and other inevitable impurities. The preparation method comprises the following steps:
(1) weighing Ti powder (D) according to the above components5034 μm) and AlV master alloy powder (D)5021 μm) and Mo powder (D)502 μm), placing in a three-dimensional blender hopper, flushing high-purity argon as protective atmosphere, and uniformly mixing for 6h to obtain mixed powder.
(2) And (3) carrying out cold isostatic pressing on the mixed powder, controlling the pressure of the cold isostatic pressing to be 220MPa, and keeping the pressure for 1min to obtain a powder pressed billet.
(3) Vacuum sintering the powder pressed billet, controlling the sintering temperature to be 1100 ℃, keeping the temperature for 2h, and keeping the vacuum degree to be lower than 8 multiplied by 10-3And Pa, cooling along with the furnace to obtain a titanium alloy sintered blank bar.
(4) Performing hot rotary forging on a titanium alloy sintered blank bar, firstly, preserving the temperature of the bar at 1100 ℃ for 30min, and then performing primary forging, wherein the deformation of the primary forging is 36%; and then, preserving the temperature of the bar at 950 ℃ for 10min, and performing finish forging, wherein the finish forging deformation is 98%, so as to obtain the heterostructure titanium alloy bar.
(5) And (3) performing stress relief annealing on the hot-swaged titanium alloy bar, wherein the annealing temperature is 350 ℃, the heat preservation time is 30min, and cooling along with the furnace to obtain the ultrahigh-strength heterostructure titanium alloy.
The ultrahigh-strength heterostructure titanium alloy prepared by the embodiment is composed of alpha titanium and beta titanium, and has no other metastable phase. The alloy microstructure is composed of an (alpha + beta) dual-phase titanium matrix and beta single-phase titanium fibers, the volume fraction of the alpha phase in the matrix is measured to be about 67%, the fiber diameter is 10-35 mu m, and the fiber spacing is 50-80 mu m. The prepared heterostructure titanium alloy has the ultrahigh tensile strength of 1696MPa and the elongation of 4 percent. Compared with the existing titanium alloy material, the ultrahigh-strength heterostructure titanium alloy obtained by the embodiment has better comprehensive mechanical properties.
Example 3
The titanium alloy with the ultrahigh-strength heterostructure comprises the following elements in percentage by mass: 3% of Al, 4.5% of V, 8% of Mo, and the balance of Ti and other inevitable impurities. The preparation method comprises the following steps:
(1) weighing Ti powder (D) according to the above components5043 μm), AlV master alloy powder (D)5027 μm) and Mo powder (D)504 μm), placing in a three-dimensional blender hopper, flushing high-purity argon as protective atmosphere, and uniformly mixing for 10h to obtain mixed powder.
(2) And (3) carrying out cold isostatic pressing on the mixed powder, controlling the pressure of the cold isostatic pressing to be 250MPa, and keeping the pressure for 2min to obtain a powder pressed billet.
(3) Vacuum sintering the powder pressed billet, controlling the sintering temperature at 1250 ℃, keeping the temperature for 2h, and keeping the vacuum degree lower than 8 multiplied by 10-3And Pa, cooling along with the furnace to obtain a titanium alloy sintered blank bar.
(4) Performing hot rotary forging on a titanium alloy sintered blank bar, firstly, preserving the temperature of the bar at 1050 ℃ for 30min, and then performing primary forging, wherein the primary forging deformation is 32%; and then, preserving the temperature of the bar stock at 910 ℃ for 10min, and performing finish forging, wherein the finish forging deformation is 91%, so as to obtain the heterostructure titanium alloy bar stock.
(5) And (3) performing stress relief annealing on the hot rotary forging titanium alloy bar, wherein the annealing temperature is 400 ℃, the heat preservation time is 45min, and cooling along with the furnace to obtain the ultrahigh-strength heterostructure titanium alloy.
The ultrahigh-strength heterostructure titanium alloy prepared by the embodiment is composed of alpha titanium and beta titanium, and has no other metastable phase. The alloy microstructure is composed of an (alpha + beta) dual-phase titanium matrix and beta single-phase titanium fibers, the volume fraction of the alpha phase in the matrix is measured to be about 61%, the fiber diameter is 20-50 mu m, and the fiber spacing is 50-70 mu m. The prepared heterostructure titanium alloy has 1510MPa of ultrahigh tensile strength and 6 percent of elongation. Compared with the existing titanium alloy material, the ultrahigh-strength heterostructure titanium alloy obtained by the embodiment has better comprehensive mechanical properties.
Example 4
The titanium alloy with the ultrahigh-strength heterostructure comprises the following elements in percentage by mass: 2.5% of Al, 4% of V, 5% of Mo, and the balance of Ti and other inevitable impurities. The preparation method comprises the following steps:
(1) weighing Ti powder (D) according to the above components5043 μm), AlV master alloy powder (D)5035 μm) and Mo powder (D)504 μm), placing in a three-dimensional blender hopper, flushing high-purity argon as protective atmosphere, and uniformly mixing for 5h to obtain mixed powder.
(2) And (3) carrying out cold isostatic pressing on the mixed powder, controlling the pressure of the cold isostatic pressing to be 180MPa, and keeping the pressure for 3min to obtain a powder pressed billet.
(3) Vacuum sintering the powder pressed billet, controlling the sintering temperature at 1200 ℃, keeping the temperature for 1h, and keeping the vacuum degree lower than 8 multiplied by 10-3Pa,And cooling along with the furnace to obtain a titanium alloy sintered blank bar.
(4) Performing hot rotary forging on a titanium alloy sintered blank bar, firstly, preserving the temperature of the bar for 30min at 1000 ℃, and then performing primary forging, wherein the deformation of the primary forging is 45%; and then, preserving the temperature of the bar stock at 930 ℃ for 10min, and performing finish forging, wherein the finish forging deformation is 86%, so as to obtain the heterostructure titanium alloy bar stock.
(5) And (3) performing stress relief annealing on the hot rotary forging titanium alloy bar, wherein the annealing temperature is 300 ℃, the heat preservation time is 45min, and cooling along with the furnace to obtain the ultrahigh-strength heterostructure titanium alloy.
The ultrahigh-strength heterostructure titanium alloy prepared by the embodiment is composed of alpha titanium and beta titanium, and has no other metastable phase. The alloy microstructure is composed of an (alpha + beta) dual-phase titanium matrix and beta single-phase titanium fibers, the volume fraction of the alpha phase in the matrix is measured to be about 74%, the fiber diameter is 25-50 mu m, and the fiber spacing is 60-100 mu m. The prepared heterostructure titanium alloy has the ultrahigh tensile strength of 1385MPa, and the elongation of 8 percent is kept. Compared with the existing titanium alloy material, the ultrahigh-strength heterostructure titanium alloy obtained by the embodiment has better comprehensive mechanical properties.
Comparative example 1
Preparing Ti-Al-V-Mo alloy according to the parameters of example 1, executing to step 3, adjusting the sintering temperature to 1300 ℃, the holding time to 5h and the vacuum degree to be lower than 5 multiplied by 10-3And Pa, cooling along with the furnace to obtain a titanium alloy sintered blank bar. And then carrying out subsequent steps of hot swaging, stress relief annealing and the like according to the parameters in the embodiment 1 to obtain the titanium alloy material.
The titanium alloy prepared in this comparative example consisted of alpha titanium and beta titanium, with no other metastable phases. As shown in FIG. 5, the SEM microstructure of the alloy shows that the alloy structure is uniform and a fibrous structure is not formed, and the volume fraction of the alpha phase in the matrix is determined to be about 68%. The tensile property curve of the alloy is shown in FIG. 6, and the tensile strength is found to be 1205MPa, and the elongation is found to be 10%. The comparative example adjusts the vacuum sintering temperature and time, so that the Mo element in the alloy is fully and uniformly diffused, a uniform microstructure is obtained, and the result shows that the tensile strength is obviously reduced compared with that of example 1. Therefore, the sintering temperature and time are important parameters of the method, and a reasonable sintering process is a precondition for forming a fiber structure and is a key for obtaining the ultrahigh-strength heterostructure titanium alloy.
Comparative example 2
A Ti-Al-V-Mo alloy was prepared according to the parameters of example 1, and the process proceeds to step 4, where the finish forging deformation is adjusted to 75% to obtain a titanium alloy bar. Then, a stress relief annealing step was performed according to the parameters in example 1 to obtain a heterostructure titanium alloy material.
The titanium alloy prepared in this comparative example consisted of alpha titanium and beta titanium, with no other metastable phases. The alloy microstructure comprises an (alpha + beta) dual-phase titanium matrix and beta single-phase titanium fibers, wherein the volume fraction of the alpha phase in the matrix is determined to be about 71%, the fiber diameter is 40-80 mu m, the fiber length is only 100-300 mu m, and the fiber spacing is 70-150 mu m. The heterostructure titanium alloy of this comparative example was measured to have a tensile strength of 1270MPa and an elongation of 8%. The comparative example reduces the finish forging deformation of the hot rotary forging process, so that the single-phase beta titanium forms a short and thick short fiber form, the strain gradient and the back stress strengthening in the alloy are not obvious, and the strength of the alloy is obviously reduced compared with that of the alloy in example 1. Therefore, the hot swaging step of the present invention requires strict control of the finish forging deformation amount to obtain a significant reinforcing effect.
Comparative example 3
The Ti-Al-V-Mo alloy is prepared according to the parameters of the embodiment 2, and the mass percent of each element is adjusted as follows: 6% of Al, 9% of V, 15% of Mo, and the balance of Ti and other inevitable impurities. The preparation process was then performed according to the parameters in example 2, with the result that sample breakage occurred during the hot swaging process of step 4, and the ultrahigh-strength heterostructure titanium alloy was not successfully prepared. The mass percentage of each alloy element is increased by the comparison example, so that the brittleness of the alloy is increased, the processing performance is reduced, and the early cracking and failure of the bar in the processing process are caused. Therefore, the mass percent of alloy elements of the ultrahigh-strength heterostructure titanium alloy needs to be controlled within a reasonable range.