1200MPa-grade high-toughness powder metallurgy titanium alloy and preparation method thereof

Abstract

The invention belongs to the field of titanium alloys, and particularly discloses a 1200 MPa-grade high-toughness powder metallurgy titanium alloy and a preparation method thereof.The preparation method comprises the following steps that alloy powder is prepared from, by mass, 3-5% of Al, 1-3% of Zr, 0-4% of Mo, 0-2% of Sn, 0-1% of Cr and the balance Ti; pressing the alloy powder into a titanium alloy cylinder; sintering the titanium alloy cylinder into a cylinder blank; and the column blank is subjected to plastic deformation, and the high-toughness titanium alloy with the shell-imitating structure is obtained. The shell-imitated structure titanium alloy single material with the alpha-phase layer wrapped by the beta transformation structure layer can be prepared, the obdurability is improved at the same time, and the application of the 1200 MPa-grade low-cost high-toughness powder metallurgy titanium alloy in advanced engineering structural parts in the fields of aerospace, ocean ships, automobiles and the like is expected to be expanded.

Description

Technical Field

[0001] The present invention belongs to the field of titanium alloys, and more specifically, relates to a 1200 MPa grade high-strength and tough powder metallurgy titanium alloy and a preparation method thereof. Background Art

[0002] Titanium and its alloys are recognized as space metals, marine metals, and biomedical metals due to their high specific strength, low elastic modulus, excellent corrosion resistance, biocompatibility, and high-temperature properties. They are now widely used in aerospace, ships, national defense, biomedicine, and other fields. With the increasingly harsh service conditions of aerospace, deep-sea, and other equipment, there is a higher demand for the strength and toughness of titanium alloys. Currently, a variety of or a large number of alloying elements are usually added to high-strength titanium alloys, and their processing methods mainly rely on melting-casting and forging. Problems such as composition segregation are difficult to eliminate, and the processing cost is high. At the same time, traditional strengthening and toughening methods usually result in a decrease in the plasticity or strength of titanium alloys, and it is difficult to break through the strength-plasticity inversion relationship. Especially when the yield strength of titanium alloys exceeds 1200 MPa, the plastic toughness decreases sharply.

[0003] Traditional strengthening and toughening means such as interstitial element control and four-state microstructure (basket weave, Widmanstatten, equiaxed, duplex) regulation are basically approaching their limits in improving strength and toughness. Although the new TRIP / TWIP toughening strategy significantly improves the toughness of titanium alloys, the yield strength is usually low. Therefore, there is an urgent need to develop new transformative structure construction strategies and preparation methods to develop 1200 MPa high-strength and tough low-cost titanium alloys.

[0004] After tens of thousands of years of evolution, some marine organisms such as shells exhibit excellent mechanical properties and toughness. The nacre of shells is a typical "brick-mortar" structure, which is alternately stacked by nanoscale aragonite lamellae and submicron-scale protein interfaces. Research shows that under impact loading, this structure can couple multiple mechanisms such as crack deflection and interface slip to increase the toughness of the material to more than 3000 times that of a single aragonite phase. This "brick-mortar" soft-hard layered cooperative design paradigm provides a bionic inspiration for breaking through the strength-toughness inversion bottleneck of materials. Current construction methods for imitating the nacreous layer structure include freeze casting, powder metallurgy, 3D printing, and rolling composite methods, etc., but there are problems such as high cost and low efficiency. In a single material, how to achieve the construction of an imitated nacreous structure is a huge challenge, which is of great significance for breaking through the current strength and toughness bottleneck of titanium alloys. Summary of the Invention

[0005] Aiming at the above defects or improvement requirements of the prior art, the present invention provides a 1200 MPa grade high-strength and tough powder metallurgy titanium alloy and a preparation method thereof, aiming to prepare a high-strength and tough titanium alloy with an imitated nacreous structure.

[0006] To achieve the above object, according to one aspect of the present invention, a preparation method of a 1200 MPa grade high-strength and tough powder metallurgy titanium alloy is provided, including the following steps:

[0007] S1. Prepare alloy powder according to the following mass fractions: Al 3 - 5 wt.%, Zr 1 - 3 wt.%, Mo 0 - 4 wt.%, Sn 0 - 2 wt.%, Cr 0 - 1 wt.%, and the balance is Ti;

[0008] S2. Press the alloy powder into a titanium alloy cylinder;

[0009] S3. Sinter the titanium alloy cylinder into a column blank;

[0010] S4. Make the column blank undergo plastic deformation to obtain a titanium alloy.

[0011] As a further preference, in step S3, the sintering temperature is 1200 - 1500 °C, the heat preservation time is 3 - 6 h, and after sintering into a column blank, it is placed in a jacket.

[0012] As a further preference, in step S4, the plastic deformation method adopts a hot extrusion process. Specifically, first place the jacketed column blank in a vacuum atmosphere furnace for heating and heat preservation, then take it out from the vacuum atmosphere furnace and place it in a preheated extrusion die for extrusion to obtain a titanium alloy.

[0013] As a further preference, when hot extruding the column blank, it is heated to 900 - 1100 °C in a vacuum atmosphere furnace, and the heat preservation time is 30 - 60 min.

[0014] As a further preference, the heat preservation temperature of the extrusion die is 400 - 500 °C, and it reaches the heat preservation temperature 2 - 4 h before hot extrusion and remains until the end of hot extrusion.

[0015] As a further preference, when hot extruding the column blank, the extrusion ratio is 4 - 16, the extrusion speed is 2 - 3 mm / s, and the extruded finished product is air-cooled to room temperature.

[0016] As a further preference, in step S2, the pressing method adopts a cold isostatic pressing process.

[0017] As a further preference, in step S2, the pressing force is 300 - 500 MPa, and the pressure holding time is 30 - 60 min.

[0018] As a further preference, in step S1, elemental powders are mechanically mixed to obtain alloy powder, the powder mixing rotation speed is 100 - 200 r / s, and the powder mixing time is 1 - 2 h.

[0019] According to another aspect of the present invention, a 1200 MPa grade high-strength and tough powder metallurgy titanium alloy is provided, which is prepared by using the above preparation method of a 1200 MPa grade high-strength and tough powder metallurgy titanium alloy.

[0020] Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention mainly have the following technical advantages:

[0021] 1. By designing the mass fractions of each element and combining pressing, sintering, and plastic forming processes, the present invention prepares a nacre-like structured titanium alloy single material in which the α-phase layer is wrapped by a β-transformed tissue layer. Among them, the β-transformed tissue layer is equivalent to the "brick" structure in nacre, and the α-phase layer is equivalent to the "mud" structure in nacre. Specifically, due to the different strain distributions of the hard β-phase and the soft α-phase during deformation, in order to coordinate the deformation, geometrically necessary dislocations accumulate at the interfaces of the β-transformed tissue layer / α-phase layer and the residual β-phase / α-phase in the β-transformed tissue layer. The accumulation of GNDs will trigger HDI stress, which continuously intensifies with the progress of deformation, thereby causing additional HDI strengthening and strain hardening, and achieving the simultaneous improvement of strength and toughness. Therefore, the present invention realizes a record-breaking combination of strength and toughness through the toughening mechanism of nacre-like structure multi-stage HDI strengthening and HDI strain hardening, breaks through the plasticity of 1200MPa grade titanium alloy, and thus realizes the perfect combination of strength and plasticity, which can expand its application in advanced engineering structural parts such as aerospace, marine ships, and the automotive field.

[0022] 2. The present invention designs the element ratios in the titanium alloy. Specifically, Al is an α-stabilizing element, Mo and Cr are β-stabilizing elements. These elements can control the ratio of the two phases during sintering and hot extrusion. Sn and Cr are neutral elements with strengthening effects. Under the ratio designed in the present invention, the ratio of the hard and soft phases (i.e., the α-phase and the β-phase) can be effectively regulated, so that it has an approximate ratio of the hard and soft phases of natural nacre. Furthermore, by combining sintering and plastic deformation, a nacre-like structure in which the α-phase layer is wrapped by a β-transformed tissue layer is formed.

[0023] 3. The present invention combines powder metallurgy and hot extrusion. During the hot extrusion process, pores in the powder metallurgy billet can be eliminated, and the material density can be increased, thereby effectively reducing the crack propagation source and improving the strength and toughness of the material. Considering that the raw material is elemental powder rather than pre-alloyed powder, in order to make the elements fully diffuse and obtain a dense billet, a higher sintering temperature and sintering time are further designed. In addition, under the conditions of the further designed extrusion temperature and holding time, the billet can be completely extruded, the material utilization rate is extremely high, and the grains do not coarsen.

[0024] 4. The present invention uses elemental powder as the raw material, and its price is lower than that of alloy powder and powder metallurgy near-net shaping, which can further reduce the preparation cost of titanium alloy, especially compared with other methods for constructing nacre-like structures. Description of the Drawings

[0025] Figure 1Schematic diagram of the microstructure evolution during the construction process of the titanium alloy imitating the shell structure in the embodiment of the present invention;

[0026] Figure 2 Engineering stress-strain curve of the titanium alloy obtained in Example 1 of the present invention at room temperature for tensile test;

[0027] Figure 3 EBSD map of the titanium alloy obtained in Example 1 of the present invention;

[0028] Figure 4 Engineering stress-strain curve of the titanium alloy obtained in Example 2 of the present invention at room temperature for tensile test;

[0029] Figure 5 Engineering stress-strain curve of the titanium alloy obtained in Example 3 of the present invention at room temperature for tensile test;

[0030] Figure 6 Engineering stress-strain curve of the titanium alloy obtained in Example 4 of the present invention at room temperature for tensile test. Detailed implementation manners

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] A preparation method of a 1200MPa grade high-strength and tough powder metallurgy titanium alloy provided by an embodiment of the present invention includes the following steps:

[0033] S1. Using elemental powders as raw materials, according to the following mass fractions: Al 3-5wt.%, Zr 1-3wt.%, Mo 0-4wt.%, Sn 0-2wt.%, Cr 0-1wt.%, and the balance is Ti (Ti 88-95wt.%), prepare a Ti-Al-Zr-Mo-Cr alloy powder system, and perform powder mixing to obtain a uniformly mixed Ti-Al-Zr-Mo-Cr alloy powder system.

[0034] S2. Press the uniformly mixed Ti-Al-Zr-Mo-Cr alloy powder system into a titanium alloy cylinder;

[0035] S3. Sinter the titanium alloy cylinder into a column blank and wrap it with a steel sleeve;

[0036] S4. Subject the column blank to plastic deformation to obtain an ultra-high strength and tough titanium alloy with a shell-like structure.

[0037] Further, the target titanium alloy is an α+β dual-phase titanium alloy; the Ti powder has a specification of 450-550 mesh, the Al powder is 8-15 μm, the Zr powder is 300-400 mesh, the Mo powder is 1-3 μm, the Sn powder is 750-850 mesh, and the Cr powder is 450-550 mesh.

[0038] Further, in step S1, mechanical powder mixing is adopted, the rotation speed is 100-200 r / s, and the powder mixing time is 1-2 h.

[0039] Further, in step S2, the cold isostatic pressing process is adopted for the pressing method, the pressing force is 300-500 MPa, and the pressure holding time is 30-60 min.

[0040] Further, in step S3, the vacuum sintering temperature is 1200-1500 °C, and the heat preservation time is 3-6 h; the steel sleeve is preferably 45 steel.

[0041] Further, in step S4, the hot extrusion process is adopted for the plastic deformation method, which specifically includes heating-insulation-extrusion.

[0042] Preferably, the hot extrusion billet is heated in a vacuum atmosphere furnace. Before heating in the vacuum atmosphere furnace, the air in the furnace is pumped out and filled with argon, and during the hot extrusion process, argon is continuously kept flowing in the furnace; the heating rate is 5-10 °C / s, the heating temperature is 900-1100 °C, and the heat preservation time is 30-60 min.

[0043] Preferably, the heat preservation temperature of the hot extrusion die is 400-500 °C, and it reaches the heat preservation temperature 2-4 h before hot extrusion and remains until the end of hot extrusion.

[0044] Preferably, the extrusion ratio during hot extrusion is 4-16, the extrusion speed is 2-3 mm / s, and the extruded finished product is air-cooled to room temperature.

[0045] The specific process is as Figure 1 shown. During the sintering heat preservation stage, a fully β crystal is formed. First, the grain boundary α phase precipitates at the grain boundaries of the furnace-cooled β crystal, and then the crystal interior transforms into a β transformation structure; subsequently, during the hot extrusion process, the heat preservation time in the β single-phase region is short, and only a partial reverse transformation of the β transformation structure to the β phase occurs. During the extrusion process, the α phase and the β phase are elongated along the extrusion direction, and during the extrusion process, the temperature drops below the β phase transformation point, and the β phase transforms into a β transformation structure. Finally, a shell-like structure is formed in which the secondary α phase layer is wrapped by the β transformation structure layer.

[0046] The following are specific examples:

[0047] Unless otherwise specified, the materials involved in the following examples can be obtained from commercial channels, and the methods are conventional methods unless otherwise specified; the corresponding units of "parts by mass" and "parts by volume" below are g and mL, respectively.

[0048] The specific test methods for the following examples are as follows: The microstructure of the specimen was observed by scanning electron microscopy; the yield strength, tensile strength, and fracture strain of the specimen were tested for tensile properties in accordance with Standard GB / T 228-2002.

[0049] Example 1

[0050] A preparation method of a low-cost ultra-high strength and toughness titanium alloy, comprising the following steps:

[0051] The raw materials used in this example are as follows: Ti powder (500 mesh), Al powder (10 μm), Zr powder (325 mesh), Mo powder (3.1 μm).

[0052] (1) Alloy powder preparation and mixing: The target alloy composition of this example is a Ti-5Al-2Zr-4Mo alloy. Using elemental powders as raw materials according to the mass ratio, and adopting the method of mechanical powder mixing, mixing at a speed of 200 r / s for 1.5 h;

[0053] (2) Pressing of alloy powder: The alloy powder in step (1) is pressed by cold isostatic pressing with a pressing force of 400 MPa for 45 min. It is pressed into a column blank with a diameter of 30 mm and a height of 30 mm;

[0054] (3) Sintering of column blank: The pressed column blank in step (2) is placed in a vacuum sintering furnace and sintered at 1300 °C for 4 h;

[0055] (4) Column blank encapsulation: The sintered column blank in step (3) is machined into a cylinder with a diameter of 27.5 mm and a height of 28 mm, and placed in a jacket made of 45 steel. The diameter of the part with the jacket is 29.5 mm and the height is 30 mm;

[0056] (5) Heating of column blank: The jacketed blank in step (4) is placed in a vacuum atmosphere furnace and kept at 1000 °C for 45 min. Among them, the vacuum atmosphere furnace needs to be filled with argon in advance, and argon is continuously introduced into the furnace during the heat preservation process;

[0057] (6) Hot extrusion forming: The blank after heat preservation in step (5) is taken out from the vacuum atmosphere furnace and quickly put into a preheated extrusion die, and extruded with an extrusion ratio of 9 to obtain a low-cost ultra-high strength and toughness titanium alloy after air cooling.

[0058] The low-cost high-strength and toughness titanium alloy prepared in this example has a shell-like structure in which the α-phase layer is wrapped by the β-transformed tissue layer, as shown in Figure 3As shown, among them, the β transformation tissue layer is equivalent to the "brick" structure in nacre, while the α-phase layer is equivalent to the "mud" structure in nacre. The room temperature tensile yield strength, tensile strength, and elongation are 1192.3 MPa, 1298.7 MPa, and 21.45% respectively, as Figure 2 shown. The plasticity of the Ti-5Al-2Zr-4Mo alloy prepared in this example is much higher than that of any titanium alloy with a similar yield strength, achieving a perfect combination of strength and plasticity.

[0059] Example 2

[0060] A preparation method of a low-cost ultra-high strength and toughness titanium alloy, comprising the following steps:

[0061] The raw materials used in this example are as follows: Ti powder (500 mesh), Al powder (10 μm), Zr powder (325 mesh), Mo powder (3.1 μm), Cr powder (500 mesh).

[0062] (1) Alloy powder configuration and mixing: The target alloy composition of this example is Ti-5Al-2Zr-4Mo-1Cr alloy. Using elemental powders as raw materials according to the mass ratio, adopting the mechanical powder mixing method, mixing at a rotation speed of 150 r / s for 2 h;

[0063] (2) Alloy powder pressing: The alloy powder in step (1) is pressed by cold isostatic pressing with a pressing force of 300 MPa for 60 min. It is pressed into a column blank with a diameter of 30 mm and a height of 30 mm;

[0064] (3) Column blank sintering: The pressed column blank in step (2) is put into a vacuum sintering furnace and sintered at 1450 °C for 5 h;

[0065] (4) Column blank encapsulation: The sintered column blank in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and put into a sleeve made of 45 steel. The diameter of the part containing the sleeve is 29.5 mm and the height is 30 mm;

[0066] (5) Column blank heating: The encapsulated blank in step (4) is put into a vacuum atmosphere furnace and kept at 1100 °C for 35 min. Among them, the vacuum atmosphere furnace needs to be filled with argon in advance, and argon is continuously introduced into the furnace during the heat preservation process;

[0067] (6) Hot extrusion forming: The blank after heat preservation in step (5) is taken out from the vacuum atmosphere furnace and quickly put into a preheated extrusion die, and extruded with an extrusion ratio of 16 to obtain a low-cost ultra-high strength and toughness titanium alloy.

[0068] The low-cost ultra-high strength and toughness titanium alloy prepared in this example has a room-temperature tensile yield strength, tensile strength, and elongation of 1307.7 MPa, 1440.6 MPa, and 9.80%, respectively, as Figure 4 shown.

[0069] Example 3

[0070] A preparation method of a low-cost ultra-high strength and toughness titanium alloy includes the following steps:

[0071] The raw materials used in this example are as follows: Ti powder (500 mesh), Al powder (10 μm), Zr powder (325 mesh).

[0072] (1) Alloy powder configuration and mixing: The target alloy composition of this example is a Ti-3Al-2Zr alloy. Using elemental powders as raw materials according to the mass ratio, mechanical powder mixing is adopted, and the mixture is rotated at a speed of 100 r / s for 3 h;

[0073] (2) Alloy powder pressing: The alloy powder in step (1) is pressed by cold isostatic pressing at a pressure of 500 MPa for 30 min. It is pressed into a column blank with a diameter of 30 mm and a height of 30 mm;

[0074] (3) Column blank sintering: The pressed column blank in step (2) is placed in a vacuum sintering furnace and sintered at 1450 °C for 5 h;

[0075] (4) Column blank encapsulation: The sintered column blank in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and placed in a jacket made of 45 steel. The diameter of the part with the jacket is 29.5 mm and the height is 30 mm;

[0076] (5) Column blank heating: The jacketed blank in step (4) is placed in a vacuum atmosphere furnace and held at 900 °C for 60 min. Among them, the vacuum atmosphere furnace needs to be filled with argon in advance, and argon is continuously introduced into the furnace during the holding process;

[0077] (6) Hot extrusion forming: The blank after holding in step (5) is taken out of the vacuum atmosphere furnace and quickly placed into a preheated extrusion die, and a sample is extruded with an extrusion ratio of 9, and the low-cost ultra-high strength and toughness titanium alloy is obtained after air cooling.

[0078] The low-cost ultra-high strength and toughness titanium alloy prepared in this example has a room-temperature tensile yield strength, tensile strength, and elongation of 975.2 MPa, 1104.8 MPa, and 14.98%, respectively, as Figure 5 shown.

[0079] Example 4

[0080] A method for preparing a low-cost ultra-high-strength and tough titanium alloy comprises the following steps:

[0081] The raw materials used in this embodiment are as follows: Ti powder (500 mesh), Al powder (10 μm), Zr powder (325 mesh), Mo powder (3.1 μm), and Sn powder (800 mesh).

[0082] (1) Alloy powder configuration and mixing: The target alloy composition of this embodiment is Ti-3Al-2Zr-4Mo-2Sn alloy. The single powder is used as the raw material according to the mass ratio, and the powder is mixed mechanically at a speed of 120 r / s for 2.5 hours;

[0083] (2) Alloy powder pressing: The alloy powder prepared in step (1) is pressed by cold isostatic pressing at a pressing force of 400 MPa for 50 min to form a column with a diameter of 30 mm and a height of 30 mm;

[0084] (3) Column blank sintering: The column blank pressed in step (2) is placed in a vacuum sintering furnace and sintered at 1450° C. for 4 h;

[0085] (4) Column blank encapsulation: The column blank sintered in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and placed in a sheath made of 45 steel. The diameter of the sheathed part is 29.5 mm and the height is 30 mm.

[0086] (5) Heating the column blank: placing the sheathed blank of step (4) into a vacuum atmosphere furnace and keeping it at 1100° C. for 35 min, wherein the vacuum atmosphere furnace needs to be filled with argon in advance, and during the insulation process, argon is introduced into the furnace throughout the entire process;

[0087] (6) Hot extrusion forming: The billet after heat preservation in step (5) is taken out from the vacuum atmosphere furnace, quickly placed in a preheated extrusion die, and the sample is extruded at an extrusion ratio of 9. After air cooling, a low-cost ultra-high strength and toughness titanium alloy is obtained.

[0088] The low-cost ultra-high-toughness titanium alloy prepared in this embodiment has a room temperature tensile yield strength, tensile strength and elongation of 1238.1 MPa, 1356.2 MPa and 13.45%, respectively. Figure 6 shown.

[0089] Example 5

[0090] A method for preparing a low-cost ultra-high-strength and tough titanium alloy comprises the following steps:

[0091] The raw materials used in this embodiment are as follows: Ti powder (500 mesh), Al powder (10 μm), Zr powder (325 mesh), Mo powder (3.1 μm), and Sn powder (800 mesh).

[0092] (1) Alloy powder preparation and mixing: The target alloy composition of this embodiment is Ti-4Al-1Zr-2Mo-0.5Cr alloy. Using elemental powders as raw materials according to the mass ratio, mechanical powder mixing is adopted, and the mixture is carried out at a rotation speed of 100 r / s for 3 h;

[0093] (2) Pressing of alloy powder: The alloy powder in step (1) is cold isostatically pressed with a pressing force of 400 MPa for 50 min. It is pressed into a cylindrical blank with a diameter of 30 mm and a height of 30 mm;

[0094] (3) Sintering of cylindrical blank: The pressed cylindrical blank in step (2) is put into a vacuum sintering furnace and sintered at 1450 °C for 4 h;

[0095] (4) Jacketing of cylindrical blank: The sintered cylindrical blank in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and put into a jacket made of 45 steel. The diameter of the part with the jacket is 29.5 mm and the height is 30 mm;

[0096] (5) Heating of cylindrical blank: The jacketed blank in step (4) is put into a vacuum atmosphere furnace and kept at 1000 °C for 35 min. Among them, the vacuum atmosphere furnace needs to be filled with argon in advance, and argon is continuously introduced into the furnace during the heat preservation process;

[0097] (6) Hot extrusion forming: The blank after heat preservation in step (5) is taken out of the vacuum atmosphere furnace and quickly put into a preheated extrusion die, and a sample is extruded with an extrusion ratio of 9, and a low-cost ultra-high strength and toughness titanium alloy is obtained after air cooling.

[0098] The low-cost ultra-high strength and toughness titanium alloy prepared in this embodiment has a room-temperature tensile yield strength, tensile strength and elongation of 1148.7 MPa, 1236.2 MPa and 15.51% respectively.

[0099] Example 6

[0100] A preparation method of a low-cost ultra-high strength and toughness titanium alloy, comprising the following steps:

[0101] The raw materials used in this embodiment are as follows: Ti powder (500 mesh), Al powder (10 μm), Zr powder (325 mesh), Mo powder (3.1 μm), Sn powder (800 mesh).

[0102] (1) Alloy powder preparation and mixing: The target alloy composition of this embodiment is Ti-3Al-3Zr-2Mo-1Sn alloy. Using elemental powders as raw materials according to the mass ratio, mechanical powder mixing is adopted, and the mixture is carried out at a rotation speed of 120 r / s for 2.5 h;

[0103] (2) Alloy powder pressing: The alloy powder prepared in step (1) is pressed by cold isostatic pressing at a pressing force of 400 MPa for 50 min to form a column with a diameter of 30 mm and a height of 30 mm;

[0104] (3) Column blank sintering: The column blank pressed in step (2) is placed in a vacuum sintering furnace and sintered at 1450° C. for 4 h;

[0105] (4) Column blank encapsulation: The column blank sintered in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and placed in a sheath made of 45 steel. The diameter of the sheathed part is 29.5 mm and the height is 30 mm.

[0106] (5) Heating the column blank: placing the encapsulated blank of step (4) into a vacuum atmosphere furnace and keeping it at 1050° C. for 40 min, wherein the vacuum atmosphere furnace needs to be filled with argon in advance, and during the insulation process, argon is introduced into the furnace throughout the entire process;

[0107] (6) Hot extrusion forming: The billet after heat preservation in step (5) is taken out from the vacuum atmosphere furnace, quickly placed in a preheated extrusion die, and the sample is extruded at an extrusion ratio of 9. After air cooling, a low-cost ultra-high strength and toughness titanium alloy is obtained.

[0108] The low-cost ultra-high strength and toughness titanium alloy prepared in this embodiment has a room temperature tensile yield strength, tensile strength and elongation of 1201.5 MPa, 1295.6 MPa and 16.23% respectively.

[0109] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a 1200MPa grade high-strength and tough powder metallurgy titanium alloy, characterized in that, It includes the following steps: S1. Prepare alloy powder according to the following mass fractions: Al 3-5 wt.%, Zr 1-3 wt.%, Mo 0-4 wt.%, Sn 0-2 wt.%, Cr 0-1 wt.%, and the balance is Ti; S2. Press the alloy powder into a titanium alloy cylinder; S3. Sinter the titanium alloy cylinder into a column blank; S4. Cause plastic deformation of the column blank to obtain titanium alloy.

2. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to claim 1, characterized in that, In step S3, the sintering temperature is 1200-1500 °C, the heat preservation time is 3-6 h, and after sintering into a column blank, it is put into a sheath.

3. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to claim 2, characterized in that, In step S4, the plastic deformation method adopts a hot extrusion process. Specifically, first put the sheathed column blank into a vacuum atmosphere furnace for heating and heat preservation, then take it out of the vacuum atmosphere furnace and put it into a preheated extrusion die, and extrude to obtain titanium alloy.

4. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to claim 3, characterized in that, When hot extruding the column blank, use a vacuum atmosphere furnace to heat it to 900-1100 °C, and the heat preservation time is 30-60 min.

5. The preparation method of the 1200MPa high-strength and tough powder metallurgy titanium alloy according to claim 3, characterized in that The heat preservation temperature of the extrusion die is 400-500 °C, and it reaches the heat preservation temperature 2-4 h before hot extrusion and remains until the end of hot extrusion.

6. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to claim 3, characterized in that, When hot extruding the column blank, the extrusion ratio is 4-16, the extrusion speed is 2-3 mm / s, and the extruded finished product is air-cooled to room temperature.

7. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to claim 1, characterized in that, In step S2, the pressing method adopts a cold isostatic pressing process.

8. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to claim 7, characterized in that, In step S2, the pressing force is 300-500 MPa, and the pressure holding time is 30-60 min.

9. The preparation method of the 1200MPa grade high-strength and tough powder metallurgy titanium alloy according to any one of claims 1-8, characterized in that, In step S1, elemental powders are mechanically mixed to obtain alloy powder, the powder mixing rotation speed is 100-200 r / s, and the powder mixing time is 1-2 h.

10. A high-strength and tough powder metallurgy titanium alloy of 1200 MPa grade, characterized in that, It is prepared by using the preparation method of a 1200 MPa grade high-strength and tough powder metallurgy titanium alloy according to any one of claims 1-9.

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