CN115109959B - Titanium alloy with double-scale equiaxial structure and preparation method and application thereof - Google Patents

Abstract

The invention discloses a titanium alloy with a dual-scale equiaxed structure and its preparation method and application. The titanium alloy microstructure includes a 10-30μm equiaxed structure region and its boundary is a continuous micron-crystalline β-Ti lath phase of 1-2μm wide and 7-40μm long. Among them, the 10-30μm equiaxed structure region includes the 100-400nm equiaxed ultra-fine-grained α-Ti phase and its grain boundary 100-150nm wide and 280-900nm long ultra-fine-grained β-Ti lath phase. The continuous micron-crystalline β-Ti lath phase and the ultra-fine-grain β-Ti lath phase constitute a dual-scale structure, and the equiaxed ultra-fine-grain α-Ti phase and the micron-scale equiaxed structural regions thereof constitute an equiaxed structure. The mechanical properties of the titanium alloy obtained by the method of the present invention are greatly improved compared with the traditional pressureless sintered titanium alloy. Compared with the existing method of preparing dual-scale structure titanium alloy, it has the advantages of simple process, low cost and high degree of freedom in product size and structure.

Description

A dual-scale equiaxed structure titanium alloy and its preparation method and application

Technical field

The invention belongs to the technical field of titanium alloys, and particularly relates to a titanium alloy with a dual-scale equiaxed structure and its preparation method and application.

Background technique

As one of the important metal structural materials, titanium and titanium alloys are the focus of development by the country and relevant researchers. They are widely used in aerospace presses, baffles, engine nacelles, reactors in the chemical industry, and electrolytic cells. Distillation towers, pipelines in the offshore engineering field, pumps for drilling, exhaust and silencer systems, springs, connecting rods in the automotive field. According to the material theory that microstructure determines macroscopic properties, by regulating the microstructure (grain size, phase distribution and morphology) of titanium alloys, its mechanical properties can be effectively optimized and the preparation of high-strength titanium alloys can be achieved.

Refining the grains to nanocrystals (<100nm) and ultra-fine grains (100-1000nm) can effectively improve the strength of titanium alloy blocks, but they usually have low plasticity due to their lack of strain hardening ability. By introducing multi-scale grain matching (such as ultra-fine grains and micron grains) into the titanium alloy matrix, the strength and plasticity of titanium alloys can be matched. At present, methods for preparing dual-scale structure titanium alloys include plastic deformation of bulk alloys-heat treatment induced recrystallization, mixed solidification of raw material powders of different sizes, amorphous crystallization-solid sintering and semi-solid sintering, and copper mold rapid solidification methods. However, the above methods all have problems such as complicated processes, limited size of the prepared bulk materials, and high preparation costs, making it difficult to popularize and apply the above high-performance materials.

Using hydrogenated titanium powder instead of pure titanium powder to form titanium materials is an important method to reduce the cost of powder metallurgy titanium materials. Titanium hydride is an intermediate product of hydrogenated and dehydrogenated titanium powder, and its cost is lower than that of pure titanium powder. In addition, the dehydrogenation effect during the titanium hydride sintering process effectively accelerates densification, making it possible to prepare high-density titanium alloy blocks without post-processing. However, titanium alloys currently prepared by pressureless sintering usually have α cluster sizes larger than 100 μm, making it difficult for the tensile strength of pressureless sintered titanium alloys to exceed 1000MPa. The reported tensile strength of the pressureless sintered Ti-6Al-4V alloy block is 830-970MPa, and the tensile plasticity is 12.5-5%. (Metallurgical and Materials Transactions A, 48 (2017) 2301–2319). Thermomechanical treatment and thermal hydrogen treatment are generally used to further improve its mechanical properties, but this also increases the preparation cost of high-performance titanium alloys and limits the freedom of size and shape of the alloy. In view of this, if the sintering process of titanium hydride or pure titanium powder can be controlled, a dual-scale coexistence of ultra-fine crystal β-Ti lath phase, micron crystal β-Ti lath phase and ultra-fine equiaxed α-Ti can be obtained. Structural titanium alloy will be able to prepare high-strength titanium alloy at low cost and realize its low-cost application in high-strength structural parts or wear-resistant structural parts in aerospace, armored vehicles, weapons, ships, automobiles and other fields, which will be of great importance. theoretical and engineering significance.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a titanium alloy with a dual-scale equiaxed structure.

Another object of the present invention lies in the preparation method of the titanium alloy with the above-mentioned dual-scale equiaxed structure.

Another object of the present invention is to provide the low-cost application of the above-mentioned dual-scale equiaxed structure titanium alloy in high-strength structural parts or wear-resistant structural parts in the fields of aerospace, armored vehicles, weapons, ships, and automobiles.

The object of the present invention is achieved through the following solutions.

A method for preparing a titanium alloy with a dual-scale equiaxed structure, including the following preparation steps:

(1) Carbon-containing treatment of alloy powder: blend the alloy element powder of the target titanium alloy composition with a carbon-containing polymer reagent, and then perform ball milling; the carbon-containing polymer reagent is a polymer liquid containing only C and H;

(2) Mixing of sintering raw materials: Mix the mixture obtained in step (1) and titanium raw material powder evenly according to the target titanium alloy composition to obtain sintering raw materials;

(3) Pressureless sintering forming: The sintered raw material obtained in step (2) is pressed and sintered to form a titanium alloy with a dual-scale equiaxed structure.

Preferably, the carbon-containing polymer reagent is one of cyclohexane and cyclohexene.

Preferably, the amount of the carbon-containing polymer reagent is 20-40 mL relative to the amount per 100 g of alloy element powder.

Preferably, the target titanium alloy is an α+β dual-phase titanium alloy; correspondingly, the alloy element powder of the target titanium alloy component is the corresponding intermediate alloy powder or metal elemental powder; the particle size of the alloy element powder is 10- 45μm.

Preferably, the ball milling equipment is QM-2SP20, the ball milling speed is 250-400rpm, the ball-to-material ratio is 5:1-20:1, and the ball milling time is 30h-50h; or other types of ball milling equipment and equivalent process parameters.

Preferably, the titanium raw material powder is pure titanium powder or titanium hydride powder TiH _x , where 0<x<2, and the particle size is 25-150 μm.

Preferably, the pressing and sintering forming method is molding-vacuum sintering or cold isostatic pressing-vacuum sintering.

Preferably,

The pressing and sintering forming method is molding-vacuum sintering; wherein, the molding pressure is 400-1000MPa, the holding time is 1-120s, the vacuum sintering temperature is 800-1500°C, and the holding time is 1-5h;

The pressing and sintering forming method is cold isostatic pressing-vacuum sintering; wherein the pressing pressure is 100-350MPa, the holding time is 1-600s, the vacuum sintering temperature is 800-1500°C, and the holding time is 1-5h.

A titanium alloy with a dual-scale equiaxed structure prepared by any of the above preparation methods.

Preferably, the titanium alloy microstructure includes an equiaxed structure region of 10-30 μm and a continuous micron-crystalline β-Ti lath phase with a boundary of 1-2 μm wide and 7-40 μm long. Among them, the 10-30 μm equiaxed structure region includes an equiaxed ultra-fine grain α-Ti phase of 100-400 nm, and an ultra-fine grain β-Ti lath phase with a grain boundary of 100-150 nm wide and 280-900 nm long. The continuous micron-crystalline β-Ti lath phase and the ultra-fine-grain β-Ti lath phase constitute a dual-scale structure, and the equiaxed ultra-fine-grain α-Ti phase and its composed micron-scale equiaxed structural regions constitute an equiaxed structure.

The above-mentioned dual-scale equiaxed structure titanium alloy is used in high-strength and wear-resistant structural parts in the fields of aerospace, armored vehicles, weapons, ships, and automobiles.

In the present invention, the carbon-containing polymer reagent is mixed with the alloy element powder and then subjected to high-energy ball milling, so that during the high-energy ball milling process, the carbon-containing polymer reagent decomposes free C and H under the collision of the grinding balls and high temperature conditions, and solidifies them. Dissolved into the alloy element powder; during the mixing and sintering process of the alloy powder containing C and H and the titanium raw material powder (pure titanium or titanium hydride powder), the free H and the H element generated by the dehydrogenation of titanium hydride volatilize under vacuum conditions, and The solid solution of C diffuses into the titanium matrix, hindering the grain boundary diffusion of β-Ti at high temperatures and providing nucleation points for the β→α phase transformation during cooling, thus forming a dual-scale equiaxed structure in which micron and ultra-fine grains coexist. Structural titanium alloy.

Compared with the existing technology, the present invention has the following advantages and technical effects:

(1) The method of the present invention can prepare ultrafine-grained β-Ti lath phase, and micron-crystalline β-Ti lath phase and ultrafine equiaxed-crystal α-Ti constitute a titanium alloy with a dual-scale equiaxed structure.

(2) The dual-scale equiaxed structure titanium alloy of the present invention has excellent mechanical properties and low preparation cost, and can be used in high-strength or wear-resistant structural parts in aerospace, armored vehicles, weapons, ships, automobiles and other fields.

Description of drawings

Figure 1 is a scanning electron microscope image of the dual-scale equiaxed structure titanium alloy obtained in Example 1.

Figure 2 is a scanning electron microscope image of the conventional pressureless sintered Ti-6Al-4V alloy obtained in Comparative Example 1.

Figure 3 is a graph showing the mechanical properties of the Ti-6Al-4V alloy obtained in Example 1 and Comparative Example 1.

Detailed ways

The present invention will be described in further detail below with reference to examples, but the implementation of the present invention is not limited thereto. The materials involved in the following examples can be obtained from commercial sources unless otherwise specified. The methods described are conventional methods unless otherwise stated. The corresponding units of "parts by mass" and "parts by volume" below are g and mL respectively.

The specific test methods of the following examples are as follows: the density of the sample is measured by the Archimedean drainage method; the microstructure of the sample is observed by a scanning electron microscope; the yield strength, tensile strength, and fracture strain of the sample are in accordance with international standards ( ChineseGB/T 228-2002) for tensile property testing.

Example 1:

A method for preparing a titanium alloy with a dual-scale equiaxed structure, including the following steps:

The raw materials used in this example are as follows: cyclohexane, titanium hydride powder (75 μm), and 60Al40V master alloy powder (45 μm).

(1) Carbon-containing treatment of alloy powder: The target alloy composition of this embodiment is Ti-6Al-4V alloy. First, pour 100 parts by mass of 60Al40V alloy powder and 20 parts by volume of cyclohexane into the stainless steel ball mill tank of the planetary ball mill (QM-2SP20). The selected stainless steel grinding ball diameters are 15mm, 10mm and 6mm respectively, and the mass ratio is 1 :3:1. The ball milling parameters are as follows: the atmosphere is high-purity argon (99.999%) at 1 atmosphere, the ball-to-material ratio is 10:1, the rotation speed is 400 rpm, and the ball milling time is 30 hours. Afterwards, the powder was taken out, dried in a vacuum drying oven for 12 hours, and then passed through a 325 mesh sieve to obtain carbon-containing 60Al40V master alloy powder.

(2) Mixing of sintering raw materials: According to the target alloy composition of Ti-6Al-4V, weigh 10 parts by mass of the carbon-containing 60Al40V master alloy powder prepared in step (1) and 93.26 parts by mass of titanium hydride powder (due to the Ti content in titanium hydride is 96.5 wt.%, so 90 parts by mass of Ti powder requires 90÷0.965=93.26 parts by mass of titanium hydride powder). Afterwards, the weighed powder is poured into the container, and the atmosphere in the container is replaced with high-purity argon gas. The powder was mixed using a V-shaped powder mixer at a rotation speed of 350 rpm for 24 h to obtain the sintered raw material powder.

(3) Pressureless sintering forming: Weigh 20 parts by mass of the sintering raw material powder mixed in step (2) and pour it into the cold pressing mold, press it with a pressing pressure of 600MPa and a holding time of 30s, and slowly demold it to obtain a green compact; After placing the green compact in the vacuum sintering furnace, use the vacuum system provided by the vacuum sintering furnace to pump the furnace to 5×10 ^-3 Pa; then, raise the temperature to 1250°C at a heating rate of 10°C/min and keep it for 4 hours; then, Cool to 650°C at a cooling rate of 10°C/min and then cool to room temperature in the furnace. Take out the sample to obtain a titanium alloy with a dual-scale equiaxed structure.

The dual-scale equiaxed structure titanium alloy prepared in this example has a density of 99.2%, and its matrix microstructure includes a 15 μm equiaxed structure region and its boundary is an average of 1.5 μm wide and 7-40 μm long continuous micron crystal β-Ti Lath phase (shown on the left in Figure 1). Among them, the 15 μm equiaxed structure region includes an equiaxed ultrafine-grained α-Ti phase with a size of about 300nm, and an ultrafine-grained β-Ti lath phase with an average grain boundary width of 140nm and a length of 280-900nm (right side of Figure 1 shown). The continuous micron-crystalline β-Ti lath phase and the ultra-fine-grain β-Ti lath phase constitute a dual-scale structure, and the equiaxed ultra-fine-grain α-Ti phase and its composed micron-scale equiaxed structural regions constitute an equiaxed structure. The room temperature tensile yield strength, tensile strength and elongation are 1170MPa, 1253MPa and 5% respectively (as shown in Figure 3). The tensile strength of the Ti-6Al-4V alloy prepared in this example is much higher than the 830-970MPa of the Ti-6Al-4V bulk alloy prepared by traditional pressureless sintering (Metallurgical and Materials Transactions A, 48 (2017) 2301–2319) , and has considerable tensile plasticity. In addition, compared with methods such as alloy plastic deformation-heat treatment induced recrystallization, mixed solidification of raw material powders of different sizes, amorphous crystallization-solid sintering and semi-solid sintering, rapid solidification of copper molds, the dual-scale equiaxed structure titanium in this embodiment The preparation method of the alloy has the advantages of simple process, low preparation cost, and unlimited shape and size of the product.

Example 2:

A method for preparing a dual-scale equiaxed structure titanium alloy, including the following steps:

The raw materials used in this example are as follows: cyclohexene, pure titanium powder (45 μm), and 60Al40V master alloy powder (10 μm).

(1) Carbon-containing treatment of alloy powder: The target alloy composition of this embodiment is Ti-6Al-4V alloy. First, pour 100 parts by mass of 60Al40V alloy powder and 40 parts by volume of cyclohexene into the stainless steel ball mill tank of the planetary ball mill (QM-2SP20). The selected stainless steel grinding ball diameters are 15mm, 10mm and 6mm respectively, and the mass ratio is 1 :3:1. The ball milling parameters are as follows: the atmosphere is 1 atmospheric pressure high-purity argon (99.999%), the ball-to-material ratio is 5:1, the rotation speed is 250rpm, and the ball milling time is 50h. Afterwards, the powder was taken out, dried in a vacuum drying oven for 12 hours, and then passed through a 325 mesh sieve to obtain carbon-containing 60Al40V master alloy powder.

(2) Mixing of sintering raw materials: According to the target alloy composition of Ti-6Al-4V, weigh 10 parts by mass of the carbon-containing 60Al40V master alloy powder prepared in step (1) and 90 parts by mass of pure titanium powder, and then weigh the powders together Pour it into a container and replace the atmosphere in the container with high-purity argon. The powder was mixed using a V-shaped powder mixer at a rotation speed of 350 rpm for 24 h to obtain the sintered raw material powder.

(3) Pressureless sintering molding: Weigh 20 parts by mass of the mixed sintering raw material powder in step (2) and pour it into the cold isostatic pressing mold, and perform cold isostatic pressing with a pressing pressure of 350MPa and a holding time of 30s. Slowly Demold the compact to obtain the compact; after placing the compact in the vacuum sintering furnace, use the vacuum system of the vacuum sintering furnace to pump the furnace to 5×10 ^-3 Pa; then, raise the temperature to 1500 °C at a heating rate of 10 °C/min. Keep warm for 1 hour; then, cool to 650°C at a cooling rate of 10°C/min and then cool to room temperature in the furnace. Take out the sample to obtain a titanium-based composite material with no Kirkendall pores and high plasticity.

The dual-scale equiaxed structure titanium alloy prepared in this example has a density of 98.7%, and its matrix microstructure includes a 30 μm equiaxed structure region and its boundary is an average of 2 μm wide and 9-35 μm long continuous micron crystal β-Ti laths. Mutually. Among them, the 30 μm equiaxed structure region includes an equiaxed ultrafine-grained α-Ti phase with a size of about 400nm, and an ultrafine-grained β-Ti lath phase with an average grain boundary width of 150nm and a length of 300-850nm. The continuous micron-crystalline β-Ti lath phase and the ultra-fine-grain β-Ti lath phase constitute a dual-scale structure, and the equiaxed ultra-fine-grain α-Ti phase and its composed micron-scale equiaxed structural regions constitute an equiaxed structure. The room temperature tensile yield strength, tensile strength and elongation are 1158MPa, 1237MPa and 6% respectively. The tensile strength of the Ti-6Al-4V alloy prepared in this example is much higher than the 830-970MPa of the Ti-6Al-4V bulk alloy prepared by traditional pressureless sintering (Metallurgical and Materials Transactions A, 48 (2017) 2301–2319). It also has considerable tensile plasticity. In addition, compared with methods such as alloy plastic deformation-heat treatment induced recrystallization, mixed solidification of raw material powders of different sizes, amorphous crystallization-solid sintering and semi-solid sintering, rapid solidification of copper molds, the dual-scale equiaxed structure titanium in this embodiment The preparation method of the alloy has the advantages of simple process, low preparation cost, and unlimited shape and size of the product.

Example 3:

A method for preparing a dual-scale equiaxed structure titanium alloy, including the following steps:

The raw materials used in this example are as follows: cyclohexene, pure titanium powder (45 μm), and 60Al40V master alloy powder (10 μm).

(1) Carbon-containing treatment of alloy powder: The target alloy composition of this embodiment is Ti-6Al-4V alloy. First, pour 100 parts by mass of 60Al40V alloy powder and 30 parts by volume of cyclohexene into the stainless steel ball mill tank of the planetary ball mill (QM-2SP20). The selected stainless steel grinding ball diameters are 15mm, 10mm and 6mm respectively, and the mass ratio is 1 :3:1. The ball milling parameters are as follows: the atmosphere is high-purity argon (99.999%) at 1 atmosphere, the ball-to-material ratio is 20:1, the rotation speed is 300 rpm, and the ball milling time is 40 hours. Afterwards, the powder was taken out, dried in a vacuum drying oven for 12 hours, and then passed through a 325 mesh sieve to obtain carbon-containing 60Al40V master alloy powder.

(2) Mixing of sintering raw materials: According to the target alloy composition of Ti-6Al-4V, weigh 10 parts by mass of the carbon-containing 60Al40V master alloy powder prepared in step (1) and 90 parts by mass of pure titanium powder, and then weigh the powders together Pour it into a container and replace the atmosphere in the container with high-purity argon. The powder was mixed using a V-shaped powder mixer at a rotation speed of 350 rpm for 24 h to obtain the sintered raw material powder.

(3) Pressureless sintering molding: Weigh 20 parts by mass of the mixed sintering raw material powder in step (2) and pour it into a cold isostatic pressing mold, and perform cold isostatic pressing with a pressing pressure of 100MPa and a holding time of 600s. Slowly Demold the compact to obtain the compact; after placing the compact in the vacuum sintering furnace, use the vacuum system of the vacuum sintering furnace to pump the furnace to 5×10 ^-3 Pa; then, raise the temperature to 1000 °C at a heating rate of 10 °C/min. Keep warm for 5 hours; then, cool to 650°C at a cooling rate of 10°C/min and then cool to room temperature in the furnace. Take out the sample to obtain a titanium-based composite material with no Kirkendall pores and high plasticity.

The dual-scale equiaxed structure titanium alloy prepared in this example has a density of 99.1%, and its matrix microstructure includes a 10 μm equiaxed structure region and its boundary is an average of 1 μm wide and 7-32 μm long continuous micron crystal β-Ti laths. Mutually. Among them, the 10 μm equiaxed structure region includes an equiaxed ultrafine-grained α-Ti phase with a size of about 100nm, and an ultrafine-grained β-Ti lath phase with an average grain boundary width of 115nm and a length of 200-780nm. The continuous micron-crystalline β-Ti lath phase and the ultra-fine-grain β-Ti lath phase constitute a dual-scale structure, and the equiaxed ultra-fine-grain α-Ti phase and its composed micron-scale equiaxed structural regions constitute an equiaxed structure. The room temperature tensile yield strength, tensile strength and elongation are 1142MPa, 1221MPa and 6% respectively. The tensile strength of the Ti-6Al-4V alloy prepared in this example is much higher than the 830-970MPa of the Ti-6Al-4V bulk alloy prepared by traditional pressureless sintering (Metallurgical and Materials Transactions A, 48 (2017) 2301–2319). It also has considerable tensile plasticity. In addition, compared with methods such as alloy plastic deformation-heat treatment induced recrystallization, mixed solidification of raw material powders of different sizes, amorphous crystallization-solid sintering and semi-solid sintering, rapid solidification of copper molds, the dual-scale equiaxed structure titanium in this embodiment The preparation method of the alloy has the advantages of simple process, low preparation cost, and unlimited shape and size of the product.

Comparative example 1:

The raw materials used in this comparative example are as follows: titanium hydride powder (75 μm), 60Al40V master alloy powder (45 μm).

(1) Mixing of sintering raw materials: According to the target alloy composition of Ti-6Al-4V, weigh 10 parts by mass of 60Al40V master alloy powder and 93.26 parts by mass of titanium hydride powder (since the Ti content in titanium hydride is 96.5wt.%, so 90 The mass parts of Ti powder require 90÷0.965=93.26 mass parts of titanium hydride powder), and then the weighed powder is poured into the container, and the atmosphere in the container is replaced with high-purity argon gas. The powder was mixed using a V-shaped powder mixer at a rotation speed of 350 rpm for 24 h to obtain the sintered raw material powder.

(2) Pressureless sintering molding: Weigh 20 parts by mass of the mixed sintering raw material powder in step (1) and pour it into the cold pressing mold, press it with a pressing pressure of 600MPa and a holding time of 30s, and slowly demold it to obtain a green compact; After placing the green compact in the vacuum sintering furnace, use the vacuum system provided by the vacuum sintering furnace to pump the furnace to 5×10 ^-3 Pa; then, raise the temperature to 1250°C at a heating rate of 10°C/min and keep it for 4 hours; then, Cool to 650°C at a cooling rate of 10°C/min and then cool to room temperature in the furnace. Take out the sample to obtain a high-strength dual-scale equiaxed structure titanium alloy.

The Ti-6Al-4V alloy matrix prepared in this comparative example is composed of long strips of α-Ti (gray phase in Figure 2) and its boundary β-Ti (white phase in Figure 2), in which the length of the α-Ti bundle is about 150 μm. . The yield strength of Ti-6Al-4V prepared in this comparative example is about 860MPa, the tensile strength is 930MPa, and the elongation is 7% (as shown in Figure 3). Its comprehensive mechanical properties are weaker than those of the high-strength dual-scale equiaxed structure titanium alloy prepared in Example 1.

Comparative example 2:

The raw materials used in this comparative example are as follows: cyclohexane, titanium hydride powder (75 μm), and 60Al40V master alloy powder (45 μm).

(1) Alloy powder mixing: The target alloy composition of this comparative example is Ti-6Al-4V alloy. First, 100 parts by mass of 60Al40V alloy powder and 20 parts by volume of cyclohexane are poured into a container, and the atmosphere in the container is replaced with high-purity argon gas. A V-shaped powder mixer was used to mix the powder at a rotation speed of 350 rpm for 24 hours to obtain the master alloy raw material powder.

(2) Mixing of sintering raw materials: According to the target alloy composition of Ti-6Al-4V, weigh 10 parts by mass of the intermediate alloy powder prepared in step (1) and 93.26 parts by mass of titanium hydride powder (since the Ti content in titanium hydride is 96.5wt .%, so 90 parts by mass of Ti powder requires 90÷0.965=93.26 parts by mass of titanium hydride powder), and then the weighed powder is poured into the container, and the atmosphere in the container is replaced with high-purity argon gas. The powder was mixed using a V-shaped powder mixer at a rotation speed of 350 rpm for 24 h to obtain the sintered raw material powder.

(3) Pressureless sintering forming: Weigh 20 parts by mass of the sintering raw material powder mixed in step (2) and pour it into the cold pressing mold, press it with a pressing pressure of 600MPa and a holding time of 30s, and slowly demold it to obtain a green compact; After placing the green compact in the vacuum sintering furnace, use the vacuum system provided by the vacuum sintering furnace to pump the furnace to 5×10 ^-3 Pa; then, raise the temperature to 1250°C at a heating rate of 10°C/min and keep it for 4 hours; then, Cool to 650°C at a cooling rate of 10°C/min, then cool to room temperature in the furnace, and take out the titanium alloy sample.

Cyclohexane that has not been ball-milled directly volatilizes during the sintering process and cannot provide nucleation points for α-Ti. The Ti-6Al-4V alloy matrix prepared in this comparative example is composed of long strips of α-Ti and its boundary β-Ti, in which the length of the α-Ti bundle is about 162 μm. The yield strength of Ti-6Al-4V prepared in this comparative example is about 857MPa, the tensile strength is 918MPa, and the elongation is 8%. Its comprehensive mechanical properties are weaker than those of the high-strength dual-scale equiaxed structure titanium alloy prepared in Example 1.

Comparative example 3:

The raw materials used in this comparative example are as follows: absolute ethanol (C ₂ H ₅ OH), titanium hydride powder (75 μm), and 60Al40V master alloy powder (45 μm).

(1) Carbon-containing treatment of alloy powder: The target alloy composition of this embodiment is Ti-6Al-4V alloy. First, pour 100 parts by mass of 60Al40V alloy powder and 20 parts by volume of absolute ethanol into the stainless steel ball mill tank of the planetary ball mill (QM-2SP20). The selected stainless steel grinding ball diameters are 15mm, 10mm and 6mm respectively, and the mass ratio is 1 :3:1. The ball milling parameters are as follows: the atmosphere is high-purity argon (99.999%) at 1 atmosphere, the ball-to-material ratio is 10:1, the rotation speed is 400 rpm, and the ball milling time is 30 hours. Afterwards, the powder was taken out, dried in a vacuum drying oven for 12 hours, and then passed through a 325 mesh sieve to obtain carbon-containing 60Al40V master alloy powder.

(2) Mixing of sintering raw materials: According to the target alloy composition of Ti-6Al-4V, weigh 10 parts by mass of the carbon-containing 60Al40V master alloy powder prepared in step (1) and 93.26 parts by mass of titanium hydride powder (due to the Ti content in titanium hydride is 96.5 wt.%, so 90 parts by mass of Ti powder requires 90÷0.965=93.26 parts by mass of titanium hydride powder). Afterwards, the weighed powder is poured into the container, and the atmosphere in the container is replaced with high-purity argon gas. The powder was mixed using a V-shaped powder mixer at a rotation speed of 350 rpm for 24 h to obtain the sintered raw material powder.

(3) Pressureless sintering forming: Weigh 20 parts by mass of the sintering raw material powder mixed in step (2) and pour it into the cold pressing mold, press it with a pressing pressure of 600MPa and a holding time of 30s, and slowly demold it to obtain a green compact; After placing the green compact in the vacuum sintering furnace, use the vacuum system provided by the vacuum sintering furnace to pump the furnace to 5×10 ^-3 Pa; then, raise the temperature to 1250°C at a heating rate of 10°C/min and keep it for 4 hours; then, Cool to 650°C at a cooling rate of 10°C/min and then cool to room temperature in the furnace. Take out the sample to obtain a titanium alloy with a dual-scale equiaxed structure.

The titanium alloy prepared in this comparative example has a density of 99.2%, and its matrix microstructure includes a 15 μm equiaxed structure region and its boundary is an average 1.2 μm wide and 10-40 μm long continuous micron-crystalline β-Ti lath phase. Among them, the 15 μm equiaxed structure region includes an equiaxed ultrafine-grained α-Ti phase with a size of about 500nm, and an ultrafine-grained β-Ti lath phase with an average grain boundary width of 145nm and a length of 200-900nm. Since the oxygen contained in ethanol is dissolved into the powder during the ball milling process and remains in the titanium alloy matrix prepared by sintering, the oxygen content of the titanium alloy prepared in this comparative example reaches 0.42 wt.%. Its tensile strength is 782MPa and has no room temperature plasticity.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, etc. may be made without departing from the spirit and principles of the present invention. All simplifications should be equivalent substitutions, and are all included in the protection scope of the present invention.

Claims (9)

1. The preparation method of the titanium alloy with the double-scale equiaxed structure is characterized by comprising the following steps of:

(1) Blending alloy element powder of a target titanium alloy component with a carbon-containing high polymer reagent, and performing ball milling; the carbon-containing macromolecular reagent is macromolecular liquid only containing C and H;

(2) Uniformly mixing the mixture obtained in the step (1) with titanium raw material powder according to the target titanium alloy component to obtain a sintering raw material;

(3) Pressing and sintering the sintering raw material obtained in the step (2) to form a titanium alloy with a double-scale equiaxed structure;

the target titanium alloy is alpha+beta titanium alloy Ti-6Al-4V; correspondingly, the alloy element powder of the target titanium alloy component is corresponding intermediate alloy powder or metal simple substance powder; the grain diameter of the alloy element powder is 10-45 mu m;

the microstructure of the titanium alloy comprises an equiaxed structure area of 10-30 mu m, and a continuous micro-crystal beta-Ti lath phase with the boundary of 1-2 mu m wide and 7-40 mu m long; wherein, the equiaxial structure area of 10-30 μm comprises an equiaxial superfine crystal alpha-Ti phase of 100-400nm and an superfine crystal beta-Ti lath phase of which the grain boundary is 100-150nm wide and 280-900nm long; the continuous micro-crystal beta-Ti lath phase and the ultra-fine crystal beta-Ti lath phase form a double-scale structure, and the equiaxed ultra-fine crystal alpha-Ti phase and a micro-scale equiaxed structure area formed by the same form an equiaxed structure.

2. The method according to claim 1, wherein the carbonaceous polymeric reagent is one of cyclohexane and cyclohexene.

3. The method of claim 1, wherein the amount of the carbonaceous polymeric reagent is 20 to 40mL per 100g of the alloying element powder.

4. The preparation method according to claim 1, wherein the ball milling equipment is QM-2SP20, the ball milling rotating speed is 250-400rpm, the ball material ratio is 5:1-20:1, and the ball milling time is 30-50h.

5. The preparation method according to claim 1, wherein the titanium raw material powder is pure titanium powder or titanium hydride powder TiH _x Wherein 0 < >xAnd < 2, the grain diameter is 25-150 μm.

6. The method of claim 1, wherein the pressing and sintering is performed by die pressing-vacuum sintering or cold isostatic pressing-vacuum sintering.

7. The method according to claim 6, wherein,

the pressing and sintering forming mode is die pressing-vacuum sintering; wherein the mould pressing pressure is 200-1000MPa, the pressure maintaining time is 1-120s, the vacuum sintering temperature is 1000-1500 ℃, and the heat preservation time is 1-5h;

or the pressing and sintering forming mode is cold isostatic pressing-vacuum sintering; wherein the pressing pressure is 50-350MPa, the dwell time is 1-600s, the vacuum sintering temperature is 1000-1500 ℃, and the heat preservation time is 1-5h.

8. A titanium alloy of a dual-scale equiaxed structure produced by the method of any one of claims 2-7.

9. The use of a titanium alloy of a double-scale equiaxed structure as claimed in claim 8 in the field of aerospace, armored vehicles, weapons, ships, automobiles and high-strength wear-resistant structural members.