1200mpa grade high strength and toughness powder metallurgy titanium alloy and preparation method thereof

Abstract

The application belongs to the field of titanium alloy, and particularly discloses a 1200MPa-grade high-strength and high-toughness powder metallurgy titanium alloy and a preparation method thereof, which comprises the following steps: alloy powder is prepared according to the following mass fractions: 3-5wt.% of Al, 1-3wt.% of Zr, 0-4wt.% of Mo, 0-2wt.% of Sn, 0-1wt.% of Cr, and the balance of Ti; the alloy powder is pressed into a titanium alloy cylinder; the titanium alloy cylinder is sintered into a column blank; and the column blank is subjected to plastic deformation to obtain a high-strength and high-toughness titanium alloy with a shell-like structure. The application can prepare a shell-like structure titanium alloy single material in which an alpha phase layer is wrapped by a beta transformed structure layer, and the strength and toughness are improved simultaneously. The 1200MPa-grade low-cost high-strength and high-toughness powder metallurgy titanium alloy is expected to expand its application in advanced engineering structural parts in the fields of aerospace, marine vessels, automobiles and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of titanium alloys, and more particularly relates to a 1200MPa high strength and toughness powder metallurgy titanium alloy and a preparation method thereof. BACKGROUND

[0002] Titanium and its alloys are considered as space metal, ocean metal and biological metal due to their high specific strength, low elastic modulus, excellent corrosion resistance, biocompatibility and high temperature performance, and have been widely used in aerospace, shipbuilding, national defense, biomedicine and other fields. With the increasingly severe service conditions of aerospace, deep sea and other equipment, there is a higher demand for the strength and toughness of titanium alloys. At present, a plurality of or a large amount of alloying elements are usually added to high-strength titanium alloys, and the processing method is mainly casting-forging, and 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 accompany the decrease of 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 alloy exceeds 1200MPa, the plasticity and toughness decrease sharply.

[0003] Traditional strengthening and toughening methods such as gap element control and four-state structure (net basket, Widmanstatten, equiaxed, dual-state) regulation basically reach the limit of the improvement of strength and toughness. Although the new TRIP / TWIP toughening strategy greatly improves the toughness of titanium alloy, the yield strength is usually low. Therefore, it is urgent to develop new revolutionary structure building strategies and preparation methods to develop 1200MPa high strength and toughness low cost titanium alloy.

[0004] After tens of thousands of years of evolution, some marine organisms such as shells show excellent mechanical properties and toughness. The nacreous layer of the shell is a typical "brick-mud" structure, which is composed of nanoscale aragonite lamellae and submicron protein interfaces alternately stacked. Studies have shown that under impact load, this structure can improve the toughness of the material by more than 3000 times that of single aragonite phase through crack deflection, interface sliding and other multi-mechanism coupling. This "brick-mud" hard-soft layered collaborative design paradigm provides a biomimetic inspiration for breaking through the strength-toughness inversion bottleneck of materials. Current methods for constructing shell-like layered structures include freeze casting, powder metallurgy, 3D printing and rolling composite method, but there are problems such as high cost and low efficiency. In a single material, how to realize the construction of a shell-like structure is a great challenge, and it is of great significance to break through the current strength and toughness bottleneck of titanium alloys. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application provides a 1200MPa high strength and toughness powder metallurgy titanium alloy and a preparation method thereof, which aims to prepare a high strength and toughness titanium alloy with a shell-like structure.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a 1200MPa-grade high-strength and high-toughness powder metallurgy titanium alloy is provided, comprising the following steps:

[0007] S1. Alloy powder was prepared 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.%, with the balance being 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. Plastic deformation is caused to the column blank to obtain titanium alloy.

[0011] As a further preferred option, in step S3, the sintering temperature is 1200-1500℃, the holding time is 3-6h, and after sintering into a column blank, it is placed in a sleeve.

[0012] As a further preferred option, in step S4, the plastic deformation method adopts a hot extrusion process. Specifically, the cladding billet is first placed in a vacuum atmosphere furnace for heating and holding, and then taken out from the vacuum atmosphere furnace and placed in a preheated extrusion die to extrude and obtain a titanium alloy.

[0013] As a further preferred option, the hot extrusion of the billet is carried out in a vacuum atmosphere furnace, heated to 900–1100°C, and held for 30–60 minutes.

[0014] As a further preferred option, the extrusion die is kept at a temperature of 400–500°C, and this temperature is reached 2–4 hours before hot extrusion and maintained until the hot extrusion is completed.

[0015] As a further preferred option, during hot extrusion of the billet, the extrusion ratio is 4 to 16, the extrusion speed is 2 to 3 mm / s, and the extruded product is air-cooled to room temperature.

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

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

[0018] As a further preferred step, in step S1, alloy powder is obtained by mechanical mixing of elemental powders, with a mixing speed of 100-200 r / s and a mixing time of 1-2 h.

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

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

[0021] 1、The present application designs the mass fraction of each element, and combines pressing, sintering and plastic forming process to prepare a single material of titanium alloy with a shell-like structure, in which the alpha phase layer is wrapped by the beta transformed structure layer, wherein the beta transformed structure layer is equivalent to the "brick" structure in the pearl layer of the shell, and the alpha phase layer is equivalent to the "mud" structure in the pearl layer of the shell. Specifically, due to the different strain distribution of hard beta phase and soft alpha phase during deformation, in order to coordinate the deformation, geometrically necessary dislocations are accumulated at the interface between the beta transformed structure layer / alpha phase layer and the residual beta phase / alpha phase in the beta transformed structure layer, and the accumulation of GNDs will trigger HDI stress and continuously intensify with deformation, thereby causing additional HDI strengthening and strain hardening, realizing the simultaneous improvement of strength and toughness. Therefore, the present application realizes a record-breaking combination of strength and toughness through the toughening mechanism of shell-like structure multi-level HDI strengthening and HDI strain hardening, breaks through the plasticity of 1200MPa grade strength titanium alloy, and realizes the perfect combination of strength and plasticity, which can expand its application in advanced engineering structural parts in the fields of aerospace, marine vessels and automobiles.

[0022] 2、The present application designs the ratio of each element in the titanium alloy. Specifically, Al is an alpha stabilizing element, Mo and Cr are beta stabilizing elements, these elements can control the proportion of two phases during sintering and hot extrusion, Sn and Cr are neutral elements with strengthening effect; under the designed ratio in the present application, the proportion of soft and hard phases (i.e. alpha phase and beta phase) can be effectively controlled, so that it has a similar proportion of soft and hard phases of natural shell. Further combined with sintering and plastic deformation, a shell-like structure is formed, in which the alpha phase layer is wrapped by the beta transformed structure layer.

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

[0024] 4、The present application uses elemental powder as raw material, which is lower in price than alloy powder and powder metallurgy near-net forming, which can further reduce the preparation cost of titanium alloy, especially compared with other shell-like structure construction methods. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1A schematic diagram of microstructure evolution in the process of constructing a shell-imitated structure of a titanium alloy according to an embodiment of the present application;

[0026] Figure 2 An engineering stress-strain curve of a titanium alloy obtained in Example 1 of the present application in a room temperature tensile test;

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

[0028] Figure 4 An engineering stress-strain curve of a titanium alloy obtained in Example 2 of the present application in a room temperature tensile test;

[0029] Figure 5 An engineering stress-strain curve of a titanium alloy obtained in Example 3 of the present application in a room temperature tensile test;

[0030] Figure 6 An engineering stress-strain curve of a titanium alloy obtained in Example 4 of the present application in a room temperature tensile test. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application 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 application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0032] The preparation method of the 1200MPa high strength and toughness powder metallurgy titanium alloy provided by the embodiment of the present application comprises the following steps:

[0033] S1, using element powder as raw material, according to the following mass fraction: Al 3-5wt.%, Zr 1-3wt.%, Mo 0-4wt.%, Sn 0-2wt.%, Cr 0-1wt.%, the balance is Ti (Ti 88-95wt.%), configure Ti-Al-Zr-Mo-Cr alloy powder, and mix the powder to obtain uniformly mixed Ti-Al-Zr-Mo-Cr alloy powder.

[0034] S2, the uniformly mixed Ti-Al-Zr-Mo-Cr alloy powder is pressed into a titanium alloy cylinder;

[0035] S3, the titanium alloy cylinder is sintered into a column blank, and a steel sleeve is wrapped;

[0036] S4, the column blank is obtained by plastic deformation to obtain a super high strength and toughness titanium alloy with a shell-imitated structure.

[0037] Further, the target titanium alloy is an α+β dual-phase titanium alloy; the Ti powder specification is 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, the step S1 adopts mechanical powder mixing, the rotating speed is 100-200 r / s, and the powder mixing time is 1-2 h.

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

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

[0041] Further, in the step S4, the hot extrusion process is adopted for the plastic deformation mode, which specifically includes heating, holding, and extrusion.

[0042] Preferably, the hot extrusion column blank is heated in a vacuum atmosphere furnace, before the heating in the vacuum atmosphere furnace, the air in the furnace is extracted, and is filled with argon, and during the hot extrusion process, the argon continuously flows in the furnace; the heating rate is 5-10 ℃ / s, the heating temperature is 900-1100 ℃, and the holding time is 30-60 min.

[0043] Preferably, the hot extrusion die holding temperature is 400-500 ℃, and the holding temperature reaches 400-500 ℃ 2-4 h before the hot extrusion, and is maintained until the end of the hot extrusion.

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

[0045] The specific process is shown in the following Figure 1 As shown in the following, the full β crystal is formed in the sintering holding stage, the grain boundary α phase is precipitated at the β crystal grain boundary, and then the intracrystalline is transformed into β transformed structure; subsequently, the hot extrusion process is in the β single-phase zone, the holding time is short, and only the partial reverse transformation of the β transformed structure to β phase occurs, the α phase and the β phase are elongated along the extrusion direction during the extrusion process, the temperature is reduced below the β phase transition point during the extrusion process, the β phase is transformed into β transformed structure, and finally the secondary α phase layer is wrapped up by the β transformed structure layer to form the imitation shell structure.

[0046] The following is a specific embodiment:

[0047] The materials involved in the following examples are available from commercial channels if no special instructions are given, and the methods are conventional methods if no special instructions are given; the units of "mass parts" and "volume parts" in the following are g and mL respectively.

[0048] The specific test method of the following examples is as follows: the microstructure of the sample is observed by a scanning electron microscope; the yield strength, tensile strength and fracture strain of the sample are tested according to the standard GB / T 228-2002.

[0049] Example 1

[0050] A preparation method of a low-cost ultrahigh 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 configuration and mixing: the target alloy composition of this example is Ti-5Al-2Zr-4Mo alloy. The elemental powders are used as raw materials and mixed at a speed of 200 r / s for 1.5 h according to the mass ratio;

[0053] (2) Alloy powder pressing: the alloy powder of step (1) is pressed by cold isostatic pressing at a pressing force of 400 MPa for 45 min. The pressed column blank has a diameter of 30 mm and a height of 30 mm;

[0054] (3) Column blank sintering: the column blank pressed in step (2) is placed in a vacuum sintering furnace and sintered at 1300℃ for 4 h;

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

[0056] (5) Column blank heating: the cladded blank of step (4) is placed in a vacuum atmosphere furnace and heated at 1000℃ for 45 min, wherein the vacuum atmosphere furnace is filled with argon in advance, and argon is continuously fed into the furnace during the heating process;

[0057] (6) Hot extrusion forming: the blank heated in step (5) is taken out from the vacuum atmosphere furnace and quickly placed into a preheated extrusion die, and then extruded at an extrusion ratio of 9 to obtain the low-cost ultrahigh strength and toughness titanium alloy after air cooling.

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

[0059] Example 2

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

[0061] 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 Cr powder (500 mesh).

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

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

[0064] (3) Column blank sintering: the column blank pressed in step (2) is placed in a vacuum sintering furnace and sintered at 1450℃ for 5h;

[0065] (4) Column blank cladding: 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 then placed in a cladding made of 45 steel. The diameter of the cladding part is 29.5 mm and the height is 30 mm;

[0066] (5) Column blank heating: the cladded blank of step (4) is placed in a vacuum atmosphere furnace and heated at 1100℃ for 35 min. The vacuum atmosphere furnace is filled with argon in advance, and argon is continuously introduced into the furnace during the heating process;

[0067] (6) Hot extrusion forming: the blank after heat preservation in step (5) is taken out from the vacuum atmosphere furnace and quickly placed into a preheated extrusion die. The sample is extruded at an extrusion ratio of 16, and the low-cost ultrahigh strength and toughness titanium alloy is obtained after air cooling.

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

[0069] Example 3

[0070] A method for preparing a low-cost super high strength and toughness titanium alloy includes the following steps:

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

[0072] (1) Alloy powder preparation and mixing: The target alloy composition of the embodiment is Ti-3Al-2Zr alloy. The elemental powders are used as raw materials and mixed at a mass ratio by using mechanical powder mixing for 3 h at a rotation speed of 100 r / s;

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

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

[0075] (4) Column blank cladding: 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 then placed in a cladding made of 45 steel, which has a diameter of 29.5 mm and a height of 30 mm;

[0076] (5) Column blank heating: The cladded blank of step (4) is placed in a vacuum atmosphere furnace and heated at 900℃ for 60 min, wherein the vacuum atmosphere furnace is filled with argon in advance, and argon is continuously supplied during the heating process;

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

[0078] The low-cost super high strength and toughness titanium alloy prepared in the embodiment has a room temperature tensile yield strength of 1307.7 MPa, a tensile strength of 1440.6 MPa, and an elongation of 9.80%, as shown in Figure 5 .

[0079] Example 4

[0080] A preparation method of a low-cost ultrahigh strength and toughness titanium alloy, comprising 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 elemental powders are used as raw materials and mixed at a mass ratio for 2.5 h at a rotation speed of 120 r / s by mechanical powder mixing;

[0083] (2) Alloy powder pressing: the alloy powder of step (1) is pressed by cold isostatic pressing at a pressing force of 400 MPa for 50 min to form a column blank 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℃ for 4h;

[0085] (4) Column blank cladding: 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 is placed in a cladding made of 45 steel, with the diameter of the cladding part being 29.5 mm and the height being 30 mm;

[0086] (5) Column blank heating: the cladded blank of step (4) is placed in a vacuum atmosphere furnace and heated at 1100℃ for 35 min, wherein the vacuum atmosphere furnace is filled with argon in advance, and argon is continuously fed into the furnace during the heating process;

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

[0088] The low-cost ultrahigh strength and 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, as shown in Figure 6 .

[0089] Embodiment 5

[0090] A preparation method of a low-cost ultrahigh strength and toughness titanium alloy, comprising 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 configuration and mixing: The target alloy composition of this embodiment is Ti-4Al-1Zr-2Mo-0.5Cr alloy. The elemental powders are used as raw materials according to the mass ratio, and are mixed by mechanical powder mixing for 3 h at a speed of 100 r / s;

[0093] (2) Alloy powder pressing: The alloy powder of step (1) is pressed by cold isostatic pressing for 50 min at a pressing force of 400 MPa. The pressed product is a column blank with a diameter of 30 mm and a height of 30 mm;

[0094] (3) Column blank sintering: The column blank prepared in step (2) is placed in a vacuum sintering furnace and sintered at 1450°C for 4 h;

[0095] (4) Column blank cladding: The column blank prepared in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and is placed in a cladding made of 45 steel. The diameter of the cladding part is 29.5 mm and the height is 30 mm;

[0096] (5) Column blank heating: The cladded blank of step (4) is placed in a vacuum atmosphere furnace and heated at 1000°C for 35 min. The vacuum atmosphere furnace is filled with argon in advance, and argon is continuously supplied during the heating process;

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

[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 method for preparing 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 configuration and mixing: The target alloy composition of this embodiment is Ti-3Al-3Zr-2Mo-1Sn alloy. The elemental powders are used as raw materials according to the mass ratio, and are mixed by mechanical powder mixing for 2.5 h at a speed of 120 r / s;

[0103] (2) Alloy powder pressing: the alloy powder of step (1) is pressed by cold isostatic pressing for 50 min at a pressing force of 400 MPa. The pressed product is a columnar blank with a diameter of 30 mm and a height of 30 mm;

[0104] (3) Columnar blank sintering: the columnar blank pressed in step (2) is placed in a vacuum sintering furnace and sintered at 1450℃ for 4h;

[0105] (4) Columnar blank cladding: the columnar blank sintered in step (3) is machined into two cylinders with a diameter of 27.5 mm and a height of 28 mm, and then placed in a cladding made of 45 steel. The diameter of the cladding containing the cladding parts is 29.5 mm, and the height is 30 mm;

[0106] (5) Columnar blank heating: the cladded blank of step (4) is placed in a vacuum atmosphere furnace and heated at 1050℃ for 40 min. The vacuum atmosphere furnace is filled with argon in advance, and argon is continuously supplied during the heating process;

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

[0108] 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 1201.5 MPa, 1295.6 MPa and 16.23%, respectively.

[0109] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a 1200MPa-grade high-strength and high-toughness powder metallurgy titanium alloy, characterized in that, Includes the following steps: S1. Alloy powder is prepared by mechanical mixing of elemental powders according to the following mass fractions: Al 3~5wt.%, Zr 1~3wt.%, Mo 2~4wt.%, Sn 0~2wt.%, Cr 0~1wt.%, with the balance being Ti. S2. Press the alloy powder into a titanium alloy cylinder; S3. Sinter the titanium alloy cylinder into a column blank; the sintering temperature is 1300~1500℃, the holding time is 3~6h, and after sintering into a column blank, it is placed in a sleeve. S4. Plastic deformation of the billet is performed to obtain titanium alloy. The plastic deformation method adopts hot extrusion process. Specifically, the billet is first placed in a vacuum atmosphere furnace and heated to 900-1100℃ and held for 30-60 minutes. Then, it is taken out from the vacuum atmosphere furnace and placed in a preheated extrusion die. The titanium alloy is extruded at an extrusion speed of 2-3 mm / s.

2. The preparation method of the 1200MPa grade high-strength and high-toughness powder metallurgy titanium alloy as described in claim 1, characterized in that, The extrusion die is kept at a temperature of 400-500℃, and this temperature is reached 2-4 hours before hot extrusion and maintained until the hot extrusion is completed.

3. The preparation method of the 1200MPa grade high-strength and high-toughness powder metallurgy titanium alloy as described in claim 1, characterized in that, When hot-extruded cylindrical blanks, the extrusion ratio is 4 to 16, and the extruded finished product is air-cooled to room temperature.

4. The method for preparing the 1200MPa grade high-strength and high-toughness powder metallurgy titanium alloy as described in claim 1, characterized in that, Step S2, the pressing method adopts cold isostatic pressing process.

5. The method for preparing the 1200MPa grade high-strength and high-toughness powder metallurgy titanium alloy as described in claim 4, characterized in that, Step S2: The pressing force is 300-500 MPa, and the holding time is 30-60 min.

6. The method for preparing 1200MPa grade high-strength and high-toughness powder metallurgy titanium alloy according to any one of claims 1-5, characterized in that, Step S1: Alloy powder is obtained by mechanical mixing of elemental powders. The mixing speed is 100-200 r / s and the mixing time is 1-2 h.

7. A 1200MPa grade high-strength and high-toughness powder metallurgy titanium alloy, characterized in that, It is prepared by the preparation method of 1200MPa grade high strength and toughness powder metallurgy titanium alloy as described in any one of claims 1-6.

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