Method for Connecting TC4 Titanium Alloy and TiAl Alloy

Abstract

The present invention relates to a method for joining titanium-based metal materials, and discloses a method for joining TC4 titanium alloy and TiAl alloy materials. The method comprises the following steps: S1, assembling a TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy to obtain a to-be-joined member; S2, performing vacuum hot pressing on the to-be-joined member. This method can effectively improve the shear strength of the alloy joint and the overall structural stability.

Description

Technical Field

[0001] The present invention relates to a method for joining titanium-based metal materials, and particularly to a method for joining TC4 titanium alloy and TiAl alloy. Background Art

[0002] Due to its properties such as low density, high specific strength, good crack propagation resistance, and corrosion resistance, TC4 titanium alloy is widely used in various industrial fields such as aerospace, shipbuilding, automotive, and medical. TiAl alloy has high specific modulus and specific strength, excellent oxidation resistance and creep resistance, and has become the most potential lightweight high-temperature structural material, mainly used in the aerospace field, such as low-pressure turbine blades of engines, aircraft skins, combustion chamber nozzles, etc. In order to give full play to the excellent performance of the two alloys, joining TC4 titanium alloy and TiAl alloy to form a composite component can save costs and increase the flexibility of applications.

[0003] Direct joining of TC4 titanium alloy and TiAl alloy will generate a large amount of brittle B2 phase and α2-Ti3Al phase intermetallic compounds in the joint, which is not conducive to improving the joint strength. There are obvious differences in the physical properties of the two materials, especially the difference in the coefficient of linear expansion, which will generate large residual stresses in the joint and affect the strength at the interface. In the prior art, an intermediate layer alloy is used to join TC4 titanium alloy and TiAl alloy, but the strength at the joint of TC4 titanium alloy and TiAl alloy still needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem that the strength at the joint of TC4 titanium alloy and TiAl alloy in the prior art needs to be improved, and to provide a method for joining TC4 titanium alloy and TiAl alloy, which can effectively improve the shear strength at the joint of the alloys and improve the overall structural stability.

[0005] To achieve the above purpose, the present invention provides a method for joining TC4 titanium alloy and TiAl alloy, the method comprising the following steps:

[0006] S1. Place a TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy and assemble to obtain a to-be-joined member;

[0007] S2. Perform vacuum hot pressing on the to-be-joined member.

[0008] Preferably, in the step S1, the atomic ratio of titanium, cobalt, copper, nickel, and vanadium in the TiCoCuNiV alloy foil is 1.1-1.3:1: 0.9-1.1:0.9-1.1:0.7-0.9.

[0009] Further preferably, the atomic ratio of titanium, cobalt, copper, nickel and vanadium in the TiCoCuNiV alloy foil is 1.15 - 1.25:1:0.95 - 1.05:0.95 - 1.05:0.75 - 0.85.

[0010] Preferably, in the TiCoCuNiV alloy foil, the atomic percentage content of titanium is 20 - 26At%, the atomic percentage of copper is 18 - 22At%, the atomic percentage of nickel is 18 - 22At%, and the atomic percentage of vanadium is 14 - 18At%.

[0011] Preferably, the preparation method of the TiCoCuNiV alloy foil includes: sequentially placing copper, nickel, cobalt, titanium and vanadium metals in a container, and then performing vacuum arc melting to obtain a TiCoCuNiV alloy ingot; cutting and polishing the TiCoCuNiV alloy ingot to obtain a TiCoCuNiV alloy foil.

[0012] Preferably, the thickness of the TiCoCuNiV alloy foil is 40 - 60μm.

[0013] Preferably, the method further includes: before placing the TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy specimens, cutting the TC4 titanium alloy and the TiAl alloy into connecting specimens.

[0014] Preferably, the steps of the vacuum hot pressing treatment include: applying a connection pressure of 5 - 15MPa to the to - be - connected parts, controlling the vacuum degree to be less than or equal to 2.5×10 -3 Pa, heating to the second temperature T2 and holding for 10 - 30min, then heating to the third temperature T3 and holding for 30 - 90min.

[0015] Further preferably, the steps of the vacuum hot pressing treatment include: applying a connection pressure of 5 - 15MPa to the to - be - connected parts, controlling the vacuum degree to be less than or equal to 2.5×10 -3 Pa, first heating to the first temperature T1 at the first heating rate, then heating to the second temperature T2 at the second heating rate and holding for 10 - 30min, and finally heating to the third temperature T3 at the third heating rate and holding for 30 - 90min, where the first heating rate is lower than the third heating rate, the third heating rate is lower than the second heating rate, the first temperature T1 is lower than the second temperature T2, and the second temperature T2 is lower than the third temperature T3.

[0016] More preferably, the method further includes: cooling the product obtained by the vacuum hot pressing treatment to the fourth temperature T4 at a cooling rate of 2 - 6℃ / min and then cooling, where the fourth temperature T4 is higher than the second temperature T2.

[0017] Further preferably, the first temperature T1 is 320 - 380 °C, the second temperature T2 is 650 - 720 °C, the third temperature T3 is 870 - 960 °C, the fourth temperature T4 is 720 - 750 °C, the first heating rate is 2 - 8 °C / min, the second heating rate is 12 - 18 °C / min, and the third heating rate is 8 - 12 °C / min.

[0018] Through the above technical solution, the method for connecting TC4 titanium alloy and TiAl alloy provided by the present invention uses a TiCoCuNiV alloy foil as an intermediate layer, which can make the elements at the joint tend to be mixed and distributed more, increase its homogenization degree, reduce the content of intermetallic compounds that may appear on the interface, and effectively improve the shear strength of the joint between TC4 titanium alloy and TiAl alloy.

[0019] In addition, the contents of Ti and V elements in TiCoCuNiV are relatively high, showing good matching with the base material, thereby promoting the mutual diffusion between elements and further improving the overall structural stability of the joint. By adjusting the hot pressing connection process parameters such as foil thickness, heating rate, and holding time, the connection temperature and the applied pressure can be effectively reduced, and while reducing the energy consumption during the alloy connection process, the deformation of the base material is also reduced. Moreover, the TiCoCuNiV alloy foil used has no precious metal elements and has a low cost. Description of the Drawings

[0020] Figure 1 is a schematic diagram of the assembly structure of the components to be connected in a specific embodiment of the present invention;

[0021] Figure 2 is the backscattered microstructure morphology of the alloy obtained in Example 1;

[0022] Figure 3 is a schematic diagram of the shear die of the component in a specific embodiment. Detailed Embodiments

[0023] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0024] As described above, the present invention provides a method for connecting TC4 titanium alloy and TiAl alloy, and the method includes the following steps:

[0025] S1. Place the TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy and assemble them to obtain the connector to be joined;

[0026] S2. Perform vacuum hot pressing on the connector to be joined.

[0027] According to the present invention, the nominal composition of the TC4 titanium alloy is Ti-6Al-4V; the nominal composition of the TiAl alloy sample is Ti-43Al-9V-0.2Y. The TiCoCuNiV alloy foil is a foil formed from an alloy containing five metal elements of titanium, cobalt, copper, nickel, and vanadium.

[0028] The inventor found during the research process that using the TiCoCuNiV alloy foil to connect the TC4 titanium alloy and the TiAl alloy can effectively improve the shear strength at the joint and the overall structural stability. In addition, the TiCoCuNiV alloy foil used does not contain precious metal elements and has a low cost.

[0029] Preferably, in the step S1, the atomic ratio of titanium, cobalt, copper, nickel, and vanadium in the TiCoCuNiV alloy foil is 1.1-1.3:1:0.9-1.1:0.9-1.1:0.7-0.9. Among them, the atomic ratio of cobalt to titanium can be 1:1.1, 1:1.12, 1:1.14, 1:1.16, 1:1.18, 1:1.2, 1:1.22, 1:1.24, 1:1.26, 1:1.28, 1:1.3, or any value within the range formed by these ratios; the atomic ratio of cobalt to copper can be 1:0.9, 1:0.92, 1:0.94, 1:0.96, 1:0.98, 1:1.0, 1:1.02, 1:1.04, 1:1.06, 1:0.08, 1:1.1, or any value within the range formed by these ratios; the atomic ratio of titanium to nickel can be 1:0.9, 1:0.92, 1:0.94, 1:0.96, 1:0.98, 1:1.0, 1:1.02, 1:1.04, 1:1.06, 1:0.08, 1:1.1, or any value within the range formed by these ratios; the atomic ratio of titanium to vanadium can be 1:0.7, 1:0.72, 1:0.74, 1:0.76, 1:0.78, 1:0.8, 1:0.82, 1:0.84, 1:0.86, 1:0.88, 1:0.9, or any value within the range formed by these ratios. It has been found that controlling the atomic ratio of cobalt, copper, nickel, titanium, and vanadium in the TiCoCuNiV alloy foil within the above range can further increase the maximum shear force that the joint of the TC4 titanium alloy and the TiAl alloy specimen can withstand. Considering further improving the shear strength of the joint between the TC4 titanium alloy and the TiAl alloy, more preferably, the atomic ratio of titanium, cobalt, copper, nickel, and vanadium in the TiCoCuNiV alloy foil is 1.15-1.25:1:0.95-1.05:0.95-1.05:0.75-0.85.

[0030] In order to further improve the shear strength of the joint between the TC4 titanium alloy and the TiAl alloy specimen, preferably, in the TiCoCuNiV alloy foil, the atomic percentage content of titanium is 22-26At%, which can be 22At%, 22.5At%, 23At%, 23.5At%, 24At%, 24.5At%, 25At%, 25.5At%, 26At%, or any value between the ranges formed by these values; the atomic percentage content of copper is 18-22At%, which can be 18At%, 19At%, 20At%, 21At%, 22At%, or any value between the ranges formed by these values; the atomic percentage content of nickel is 18-22At%, which can be 18At%, 19At%, 20At%, 21At%, 22At%, or any value between the ranges formed by these values; the atomic percentage content of vanadium is 14-18At%, which can be 14At%, 14.5At%, 15At%, 15.5At%, 16At%, 16.5At%, 17At%, 17.5At%, 18At%, or any value between the ranges formed by these values.

[0031] The TiCoCuNiV alloy foil can be prepared by cutting the TiCoCuNiV melting alloy, or obtained by rolling the TiCoCuNiV melting alloy. Preferably, the preparation method of the TiCoCuNiV alloy foil includes: placing copper, nickel, cobalt, titanium and vanadium metals in a container in sequence, and then performing vacuum arc melting to obtain a TiCoCuNiV alloy ingot; cutting and polishing the TiCoCuNiV alloy ingot to obtain the TiCoCuNiV alloy foil. The alloy foil prepared by the above method has a more uniform thickness, and can accurately control the thickness of the connecting piece while simplifying the steps, thereby further improving the shear strength at the joint between the TC4 titanium alloy and the TiAl alloy.

[0032] According to the present invention, the copper, nickel, cobalt, titanium and vanadium metals can be in the form of metal particles. The container can be any feasible container. As a specific embodiment of the present invention, the container is a crucible. The order of placing the copper, nickel, cobalt, titanium and vanadium metals in the container is based on the melting points of the metal materials. The metal material with a lower melting point is placed at the bottom of the container, and then other metal materials are placed in the order of increasing melting point, and the metal material with the highest melting point is placed at the top.

[0033] Preferably, the method further includes: before placing the TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy, cleaning the TiCoCuNiV alloy foil, which can further improve the connection effect between the TC4 titanium alloy and the TiAl alloy. The cleaning can adopt any feasible cleaning method in the prior art, such as cleaning, ultrasonic cleaning, etc. Preferably, it is ultrasonic cleaning. The cleaning solution used for cleaning can be selected from at least one of ethanol, acetone, and water, and preferably ethanol.

[0034] According to the present invention, in order to make the raw materials mix more evenly and further improve the shear strength of the joint between the TC4 titanium alloy and the TiAl alloy, the current of vacuum arc melting is 280 - 310 A, the voltage is 380 V, the arc is maintained for 40 - 60 S, and each time the alloy is melted, it is cooled and then flipped for melting after cooling, and this is repeated more than 5 times.

[0035] Preferably, the thickness of the TiCoCuNiV alloy foil is 40 - 60 μm, and it can be 40 μm, 44 μm, 48 μm, 52 μm, 56 μm, 60 μm, or any value within the range formed by these values. Controlling the thickness of the TiCoCuNiV alloy foil within the above range can further improve the shear strength of the joint between the TC4 titanium alloy and the TiAl alloy.

[0036] Preferably, the method further includes: before placing the TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy specimens, cutting the TC4 titanium alloy block and the TiAl alloy block. It can improve the contact effect among the TC4 titanium alloy specimen, the TiAl alloy specimen, and the TiCoCuNiV alloy foil, thereby further improving the shear strength of the joint between the TC4 titanium alloy and the TiAl alloy. The parallelism of the upper and lower surfaces of the cut specimen is less than or equal to 0.02 mm, and the surface roughness of the TiCoCuNiV alloy foil is Ra0.2 - 0.4. By controlling the roughness and parallelism of the TC4 titanium alloy and the TiAl alloy before connection, the size of the composite component obtained after connection can be effectively controlled, and there is no need to further process the component after connection, which simplifies the processing process while ensuring the accuracy of the composite component.

[0037] Preferably, the method further includes: performing a grinding and polishing treatment on the cut specimen, which can further improve the contact effect among the TC4 titanium alloy specimen, the TiAl alloy specimen, and the TiCoCuNiV alloy foil. Further preferably, the polished specimen is cleaned.

[0038] According to the present invention, polishing can be carried out in any feasible manner. As a specific embodiment of the present invention, diamond grinding paste is used for mechanical polishing, and ultrasonic cleaning is used for cleaning. Preferably, the solvent used for cleaning is ethanol.

[0039] Preferably, the sandpaper used for grinding is 360 - 3000# SiC sandpaper. The grinding process includes: successively grinding the welding surfaces of the TC4 titanium alloy and TiAl alloy specimens with 360 - 3000# SiC sandpaper step by step. This can improve the contact effect between the TC4 titanium alloy specimen, TiAl alloy specimen, and TiCoCuNiV alloy foil, thereby further improving the shear strength at the joint of the TC4 titanium alloy and TiAl alloy specimens.

[0040] In order to further improve the shear strength at the joint of the TC4 titanium alloy and TiAl alloy specimens, preferably, before the cutting, the TC4 titanium alloy is subjected to cold rolling and annealing treatment. Further preferably, the conditions of the annealing treatment include: the temperature is 750 - 930 °C, and the time is 1 - 2.5 h. More preferably, the conditions of the annealing treatment include: the temperature is 780 - 900 °C, and the time is 1.5 - 2 h.

[0041] Preferably, the cutting process includes: the size of the TC4 titanium alloy specimen after cutting is 28 - 32 mm × 18 - 22 mm × 4 - 6 mm, and the size of the TiAl alloy specimen after cutting is 18 - 22 mm × 14 - 16 mm × 3 - 4 mm. As a specific embodiment of the present invention, the TC4 titanium alloy is cut into a size of 30 mm × 20 mm × 5 mm using a wire electrical discharge machine, and the TiAl alloy is cut into a size of 20 mm × 15 mm × 3 mm using a cutting machine.

[0042] Preferably, the method further includes: after the cleaning is completed, use a hair dryer to dry the surface.

[0043] Preferably, the steps of the vacuum hot pressing treatment include: applying a connection pressure of 5 - 15 MPa to the connection parts to be joined, controlling the vacuum degree to be less than or equal to 2.5×10 -3 Pa, heating to the second temperature T2 and maintaining for 10 - 30 min, and then heating to the third temperature T3 and maintaining for 30 - 90 min. By performing the vacuum hot pressing treatment through the above method, the contact degree of the connection parts can be effectively increased, and the shear strength at the joint of the TC4 titanium alloy and TiAl alloy specimens can be further improved. Considering that the shear strength at the joint of the TC4 titanium alloy and TiAl alloy specimens can be further improved, further preferably, the steps of the vacuum hot pressing treatment include: applying a connection pressure of 5 - 15 MPa to the connection parts to be joined, controlling the vacuum degree to be less than or equal to 2.5×10 -3Pa, first heat it to the first temperature T1 at the first heating rate, then heat it to the second temperature T2 at the second heating rate and hold for 10 - 30 min, and finally heat it to the third temperature T3 at the third heating rate and hold for 30 - 90 min. The first heating rate is lower than the third heating rate, the second heating rate is lower than the second heating rate, the first temperature T1 is lower than the second temperature T2, and the second temperature T2 is lower than the third temperature T3.

[0044] Preferably, the method further includes: cooling the product obtained by the vacuum hot pressing treatment to the fourth temperature T4 at a cooling rate of 2 - 6 °C / min and then directly cooling it. The fourth temperature T4 is higher than the second temperature T2. It is found that the shear strength of the joint between the TC4 titanium alloy and TiAl alloy specimens obtained by the above method is higher. Considering that the shear strength of the joint between the TC4 titanium alloy and TiAl alloy specimens can be further improved, further preferably, the first temperature T1 is 320 - 380 °C, which can be 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, or any value within the range formed by these temperatures; the second temperature T2 is 650 - 720 °C, which can be 650 °C, 660 °C, 670 °C, 680 °C, 690 °C, 700 °C, 710 °C, 720 °C, or any value within the range formed by these temperatures; the third temperature T3 is 870 - 960 °C, which can be 870 °C, 890 °C, 910 °C, 920 °C, 940 °C, 960 °C, or any value within the range formed by these temperatures; the fourth temperature T4 is 720 - 760 °C, which can be 720 °C, 730 °C, 740 °C, 750 °C, 760 °C, or any value within the range formed by these temperatures; the first heating rate is 2 - 8 °C / min, which can be 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, or any value within the range formed by these values; the second heating rate is 12 - 18 °C / min, which can be 12 °C / min, 13 °C / min, 14 °C / min, 15 °C / min, 16 °C / min, 17 °C / min, 18 °C / min, or any value within the range formed by these values.

[0045] Preferably, the heating rate to the third temperature T3 is 8 - 12 °C / min, and the cooling rate to the fourth temperature T4 is 2 - 6 °C / min.

[0046] Considering that the shear strength of the joint between the TC4 titanium alloy and TiAl alloy specimens can be further improved, further preferably, the third temperature T3 is 930 - 960 °C.

[0047] In order to further improve the shear strength of the joint between the TC4 titanium alloy and the TiAl alloy specimen, preferably, the connection pressure is 10 - 15 MPa.

[0048] According to a particularly preferred embodiment of the present invention, a method for joining the TC4 titanium alloy and the TiAl alloy is provided, comprising the following steps:

[0049] S1. Anneal the cold-rolled TC4 titanium alloy at a temperature of 890 °C for 1.5 h, then cut it into alloy specimen blocks, and perform grinding, polishing, ultrasonic cleaning and surface drying on the surface to be welded to obtain the TC4 titanium alloy block to be welded;

[0050] Cut the TiAl alloy after ingot forging into alloy blocks, and perform grinding, polishing, ultrasonic cleaning and drying on the surface to be joined to obtain the TiAl alloy block to be welded;

[0051] S2. Calculate the masses of titanium, cobalt, copper, nickel and vanadium according to the atomic ratio of 1.1 - 1.3:1: 0.9 - 1.1:0.9 - 1.1:0.7 - 0.9, calculate and weigh the bulk metal raw materials according to the total mass of 400 g of ingot, the purity of the metal raw materials is 99.99%, place the melting raw materials in the crucible in order of melting point from high to low, and perform melting in a vacuum induction arc furnace. The current of the vacuum arc melting is 280 - 310 A, the voltage is 380 V, the arc is maintained for 40 - 60 S, and after each melting, the alloy is cooled and then flipped for melting, and the melting is repeated more than 5 times to make a TiCoCuNiV alloy ingot with uniform composition;

[0052] Cut the TiCoCuNiV alloy ingot into thin sheets with a thickness of 0.3 - 0.5 mm, and grind and mechanically polish it to a thickness of 40 - 60 μm. After ultrasonic cleaning, dry the surface, place the obtained TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy and put it into a graphite mold for assembly to obtain the workpiece to be joined;

[0053] S3. Put the workpiece to be joined into a vacuum hot press sintering furnace, apply a connection pressure of 5 - 15 MPa to the specimen to be welded. When the vacuum degree in the furnace drops to below 2.5×10 -3 Pa, heat it up to 320 - 380 °C at a heating rate of 2 - 8 °C / min, then heat it up to 650 - 720 °C at a heating rate of 12 - 18 °C / min, and keep it at this temperature for 10 - 30 min, then heat it to 870 - 960 °C at a rate of 8 - 12 °C / min and keep it for 30 - 90 min for hot press connection;

[0054] S4. After the connection is completed, first cool it at a rate of 2 - 6 °C / min to 720 - 760 °C, then cool it with the furnace to room temperature and unload the pressure to take out the alloy.

[0055] The method for connecting TC4 titanium alloy and TiAl alloy provided by the present invention uses a TiCoCuNiV alloy foil as an intermediate layer. By designing and changing the atomic ratio of the elements in the intermediate layer, the elements at the joint tend to be more mixedly distributed, increasing its homogenization degree and reducing the content of intermetallic compounds that may appear on the interface, which can effectively improve the shear strength of the joint between TC4 titanium alloy and TiAl alloy.

[0056] The contents of Ti and V elements in the intermediate layer are relatively high and show good matching with the base material, thereby promoting the mutual diffusion between elements and improving the overall structural stability of the joint.

[0057] By adjusting the hot pressing connection process parameters such as foil thickness, heating rate, and holding time, the connection temperature and the applied pressure can be effectively reduced, thereby reducing the energy consumption during the alloy connection process while reducing the deformation of the base material. By controlling the roughness and parallelism of the TC4 titanium alloy and TiAl alloy specimens before connection, the dimensions of the composite component obtained after connection can be effectively controlled, and further processing of the component is not required after connection, which simplifies the processing process while ensuring the accuracy of the composite component. In addition, the TiCoCuNiV alloy foil used has no precious metal elements and has a low cost.

[0058] The present invention will be described in detail below through embodiments. In the following embodiments, the raw materials of titanium, cobalt, copper, nickel, vanadium, iron, and aluminum are high-purity metal particles from Zhongnuo New Materials, and the purity of the raw materials is 99.99%.

[0059] Preparation Example 1

[0060] Put titanium, cobalt, copper, nickel, and vanadium into a crucible in the order of increasing melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain TiCoCuNiV ingot-1;

[0061] Among them, the atomic percentage of Ti is 24%, the atomic percentage of Co is 20%, the atomic percentage of Cu is 20%, the atomic percentage of Ni is 20%, and the atomic percentage of V is 16%.

[0062] Preparation Example 2

[0063] Put titanium, cobalt, copper, nickel, and vanadium into a crucible in the order of increasing melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain TiCoCuNiV ingot-2;

[0064] Among them, the atomic percentage of Ti is 23%, the atomic percentage of Co is 20%, the atomic percentage of Cu is 19%, the atomic percentage of Ni is 21%, and the atomic percentage of V is 17%.

[0065] Preparation Example 3

[0066] Put titanium, cobalt, copper, nickel and vanadium into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain the TiCoCuNiV ingot - 3;

[0067] Among them, the atomic percentage of Ti is 25%, the atomic percentage of Co is 20%, the atomic percentage of Cu is 21%, the atomic percentage of Ni is 19%, and the atomic percentage of V is 15%.

[0068] Preparation Example 4

[0069] Put titanium, cobalt, copper, nickel and vanadium into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain the TiCoCuNiV ingot - 4;

[0070] Among them, the atomic percentage of Ti is 22%, the atomic percentage of Co is 20%, the atomic percentage of Cu is 18%, the atomic percentage of Ni is 22%, and the atomic percentage of V is 18%.

[0071] Preparation Example 5

[0072] Put titanium, cobalt, copper, nickel and vanadium into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain the TiCoCuNiV ingot - 5;

[0073] Among them, the atomic percentage of Ti is 26%, the atomic percentage of Co is 20%, the atomic percentage of Cu is 22%, the atomic percentage of Ni is 18%, and the atomic percentage of V is 14%.

[0074] Preparation Example 6

[0075] Put titanium, cobalt, copper and nickel into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain the TiCoCuNi ingot;

[0076] Among them, the atomic percentage of Ti is 23.8%, the atomic percentage of Co is 25.4%, the atomic percentage of Cu is 25.4%, and the atomic percentage of Ni is 25.4%.

[0077] Preparation Example 7

[0078] Put titanium, cobalt, copper and vanadium into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain a TiCoCuV ingot;

[0079] Among them, the atomic percentage of Ti is 30%, the atomic percentage of Co is 25%, the atomic percentage of Cu is 25%, and the atomic percentage of V is 20%.

[0080] Preparation Example 8

[0081] Put titanium, cobalt, nickel and vanadium into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain a TiCoNiV ingot;

[0082] Among them, the atomic percentage of Ti is 30%, the atomic percentage of Co is 25%, the atomic percentage of Ni is 25%, and the atomic percentage of V is 20%.

[0083] Preparation Example 9

[0084] Put titanium, cobalt, copper, nickel and iron into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain a TiCoCuNiFe ingot;

[0085] Among them, the atomic percentage of Ti is 23%, the atomic percentage of Co is 20%, the atomic percentage of Cu is 20%, the atomic percentage of Ni is 20%, and the atomic percentage of Fe is 17%.

[0086] Preparation Example 10

[0087] Put cobalt, nickel and iron into the crucible in ascending order of melting point, and then place it in a vacuum induction arc furnace for melting. After each melting, wait for the alloy to cool and then turn it over for melting. Repeat the melting 5 times to obtain a CoNiFe ingot;

[0088] Among them, the atomic percentage of Co is 28%, the atomic percentage of Ni is 45%, and the atomic percentage of Fe is 27%.

[0089] Example 1

[0090] S1. First, anneal the cold-rolled TC4 titanium alloy at 890 °C for 2 h, and then cut it into alloy blocks of 30 mm × 20 mm × 5 mm; cut the TiAl alloy into alloy blocks of 20 mm × 15 mm × 3 mm; gradually polish the surface to be welded with 360 - 2000# SiC sandpaper, mechanically polish it with water-soluble diamond grinding paste, and place it in absolute ethanol for ultrasonic cleaning for 10 min, then dry the surface to obtain the TC4 titanium alloy specimen block and TiAl alloy specimen block to be joined;

[0091] S2. Cut the TiCoCuNiV alloy ingot - 1 into thin slices with a thickness of 0.3 mm, and gradually polish and polish it into a foil with a thickness of 50 μm (±5 μm) with 360 - 2000# SiC sandpaper, the surface roughness ≤ Ra0.4, and the parallelism of the upper and lower surfaces ≤ 0.02 mm. Then place the foil between the TC4 titanium alloy block and the TiAl alloy block (see Figure 1 ), put it into a graphite mold for assembly to obtain the workpiece to be joined;

[0092] S3. Put the workpiece to be joined into a vacuum hot-pressing sintering furnace, apply a pressure of 5 MPa to the specimen to be welded. When the vacuum degree in the furnace drops below 2.5×10 -3 Pa, heat it up to 350 °C at a heating rate of 5 °C / min, then heat it up to 700 °C at a heating rate of 15 °C / min, and keep it at 700 °C for 20 min, then heat it to 870 °C at a rate of 10 °C / min and keep it for 60 min for joining;

[0093] S4. After the joining is completed, cool it down to 720 °C at a rate of 5 °C / min, then cool it in the furnace to room temperature and unload the pressure to take out the alloy.

[0094] Use a scanning electron microscope to observe the interfacial microstructure of the joint between the TC4 titanium alloy and the TiAl alloy prepared in Example 1, and obtain Figure 2 . Through Figure 2 the interfacial microstructure, it can be seen that the interfacial microstructure at the joint between the TiCoCuNiV alloy and the TiAl alloy and the TC4 titanium alloy is uniform, the weld seam is flat, and there are no obvious welding defects. The diffusion zone on one side of the TiCoCuNiV alloy and the TiAl alloy can be divided into three joining layers. The first layer is mainly the β / B2 phase formed by the diffusion of elements in the TiCoCuNiV alloy into the TiAl alloy. The second layer is dark gray and consists of the Al(Cu,Ni)Ti phase, while the light gray joining layer is the Al(Co,Ni)2Ti phase.

[0095] From Figure 2It can be seen that the bonding region between the TiCoCuNiV alloy and TC4 consists of two bonding layers. It can be observed that the bonding layer on the TC4 titanium alloy side is thicker and is composed of long strip torn α-Ti phases and large β-Ti phases, belonging to Widmanstätten structure. This is because the Co, Cu, and Ni elements in the TiCoCuNiV alloy diffuse into TC4, reducing the β-phase transformation temperature of TC4 and promoting the growth of α-Ti and β-Ti, making the β grains at the interface coarser. Through the analysis of the tissue interface between TC4 and the TiCoCuNiV intermediate layer, the interface layer is mainly composed of Ti-rich intermetallic compounds and a small amount of Ti2Ni phases. In the entire joint region, the microstructure of the TiCoCuNiV alloy intermediate layer is mainly composed of face-centered cubic phase and body-centered cubic phase. The face-centered cubic phase includes bright white Cu-rich phase and light gray (Ni,Ti)-rich face-centered cubic phase, and the body-centered cubic phase is mainly the dark gray body-centered cubic matrix phase. The TiCoCuNiV alloy intermediate layer exists in the form of solid solution inside.

[0096] Example 2

[0097] Connect the alloys according to the method of Example 1. The difference is that step S3 includes: putting the parts to be joined into a vacuum hot pressing sintering furnace, applying a pressure of 5 MPa to the specimens to be welded. Wait until the vacuum degree in the furnace drops below 2.5×10 -3 Pa, heat up to 350 °C at a heating rate of 5 °C / min, then heat up to 700 °C at a heating rate of 15 °C / min, and hold for 20 min at 700 °C. Then heat up to 900 °C at a rate of 10 °C / min and hold for 60 min for connection.

[0098] Example 3

[0099] Connect the alloys according to the method of Example 1. The difference is that step S3 includes: putting the parts to be joined into a vacuum hot pressing sintering furnace, applying a pressure of 5 MPa to the specimens to be welded. Wait until the vacuum degree in the furnace drops below 2.5×10 -3 Pa, heat up to 350 °C at a heating rate of 5 °C / min, then heat up to 700 °C at a heating rate of 15 °C / min, and hold for 20 min at 700 °C. Then heat up to 930 °C at a rate of 10 °C / min and hold for 60 min for connection.

[0100] Example 4

[0101] Connect the alloys according to the method of Example 1. The difference is that step S3 includes: putting the parts to be joined into a vacuum hot pressing sintering furnace, applying a pressure of 5 MPa to the specimens to be welded. Wait until the vacuum degree in the furnace drops below 2.5×10 -3Below Pa, heat at a heating rate of 5 °C / min to 350 °C, then heat at a heating rate of 15 °C / min to 700 °C, hold at 700 °C for 20 min, then heat at a rate of 10 °C / min to 960 °C, hold for 60 min, and perform the connection.

[0102] Example 5

[0103] Connect the alloy according to the method of Example 1. The difference is that step S3 includes: placing the parts to be connected into a vacuum hot pressing and sintering furnace, applying a pressure of 10 MPa to the specimens to be welded, waiting until the vacuum degree in the furnace drops to 2.5×10 -3 Below Pa, heat at a heating rate of 5 °C / min to 350 °C, then heat at a heating rate of 15 °C / min to 700 °C, hold at 700 °C for 20 min, then heat at a rate of 10 °C / min to 960 °C, hold for 60 min, and perform the connection.

[0104] Example 6

[0105] Connect the alloy according to the method of Example 1. The difference is that step S3 includes: placing the parts to be connected into a vacuum hot pressing and sintering furnace, applying a pressure of 15 MPa to the specimens to be welded, waiting until the vacuum degree in the furnace drops to 2.5×10 -3 Below Pa, heat at a heating rate of 5 °C / min to 350 °C, then heat at a heating rate of 15 °C / min to 700 °C, hold at 700 °C for 20 min, then heat at a rate of 10 °C / min to 960 °C, hold for 60 min, and perform the connection.

[0106] Example 7

[0107] Connect the alloy according to the method of Example 5. The difference is that step S3 includes: placing the parts to be connected into a vacuum hot pressing and sintering furnace, applying a pressure of 10 MPa to the specimens to be welded, waiting until the vacuum degree in the furnace drops to 2.5×10 -3 Below Pa, heat at a heating rate of 5 °C / min to 650 °C, hold at 650 °C for 20 min, then heat at a rate of 10 °C / min to 960 °C, hold for 60 min, and perform the connection.

[0108] Example 8

[0109] Connect the alloy according to the method of Example 5. The difference is that step S3 includes: the holding time after heating to 960 °C is 30 min.

[0110] Example 9

[0111] Connect the alloy according to the method of Example 5. The difference is that step S3 includes: the holding time after heating to 960 °C is 90 min.

[0112] Example 10

[0113] Connect the alloy according to the method of Example 5, except that in step S2, it is polished into a foil with a thickness of 30 μm (±5 μm).

[0114] Example 11

[0115] Connect the alloy according to the method of Example 5, except that in step S2, it is polished into a foil with a thickness of 40 μm (±5 μm).

[0116] Example 12

[0117] Connect the alloy according to the method of Example 5, except that in step S2, it is polished into a foil with a thickness of 60 μm (±5 μm).

[0118] Example 13

[0119] Connect the alloy according to the method of Example 5, except that in step S2, it is polished into a foil with a thickness of 70 μm (±5 μm).

[0120] Example 14

[0121] Connect the alloy according to the method of Example 5, except that the TiCoCuNiV alloy ingot - 1 is replaced with the TiCoCuNiV alloy ingot - 2.

[0122] Example 15

[0123] Connect the alloy according to the method of Example 5, except that the TiCoCuNiV alloy ingot - 1 is replaced with the TiCoCuNiV alloy ingot - 3.

[0124] Example 16

[0125] Connect the alloy according to the method of Example 5, except that the TiCoCuNiV alloy ingot - 1 is replaced with the TiCoCuNiV alloy ingot - 4.

[0126] Example 17

[0127] Connect the alloy according to the method of Example 5, except that the TiCoCuNiV alloy ingot - 1 is replaced with the TiCoCuNiV alloy ingot - 5.

[0128] Example 18

[0129] Connect the alloy according to the method of Example 1, except that step S4 includes: after the connection is completed, the temperature is decreased to 690 °C at a rate of 5 °C / min, and then cooled to room temperature in the furnace and the pressure is unloaded to take out the alloy.

[0130] Comparative Example 1

[0131] Connect the alloy according to the method of Example 1, except that the TiCoCuNiV alloy ingot - 1 is replaced with a TiCoCuNi ingot.

[0132] Comparative Example 2

[0133] Connect the alloy according to the method of Example 1, except that the TiCoCuNiV alloy ingot - 1 is replaced with a TiCoCuV ingot.

[0134] Comparative Example 3

[0135] Connect the alloy according to the method of Example 1, except that the TiCoCuNiV alloy ingot - 1 is replaced with a TiCoNiV ingot.

[0136] Comparative Example 4

[0137] Connect the alloy according to the method of Example 1, except that the TiCoCuNiV alloy ingot - 1 is replaced with a TiCoCuNiFe ingot.

[0138] Comparative Example 5

[0139] Connect the alloy according to the method of Example 1, except that the TiCoCuNiV alloy ingot - 1 is replaced with a CoNiFe ingot.

[0140] Test Example

[0141] The joined test blocks in the above - mentioned examples and comparative examples were tested for shear strength using a mold (see Figure 3 ), the test instrument was an INSTRON5969 electronic universal material testing machine, and the loading speed was 0.5 mm / min. The results are shown in Table 1.

[0142] Table 1

[0143]

[0144] It can be seen from the results in Table 1 that the shear strengths of the examples are all greater than those of the comparative examples, indicating that using the method provided by the present invention to connect TC4 titanium alloy and TiAl alloy can effectively improve the shear strength of the joint, facilitating subsequent applications.

[0145] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for connecting TC4 titanium alloy and TiAl alloy, characterized in that The method includes the following steps: S1. Assemble a TiCoCuNiV alloy foil between a TC4 titanium alloy and a TiAl alloy to obtain a connector to be joined; the atomic ratio of titanium, cobalt, copper, nickel, and vanadium in the TiCoCuNiV alloy foil is 1.1 - 1.3:1:0.9 - 1.1:0.9 - 1.1:0.7 - 0.9; S2. Conduct vacuum hot pressing on the connector to be joined; The steps of the vacuum hot pressing treatment include: applying a connection pressure of 5-15 MPa to the to-be-connected parts, controlling the vacuum degree to be less than or equal to 2.5×10 -3 Pa, first rising to the first temperature T1 at the first heating rate, then rising to the second temperature T2 at the second heating rate and maintaining for 10-30 min, and finally rising to the third temperature T3 at the third heating rate and maintaining for 30-90 min. The first heating rate is lower than the third heating rate, the third heating rate is lower than the second heating rate, the first temperature T1 is lower than the second temperature T2, the second temperature T2 is lower than the third temperature T3, the first temperature T1 is 320-380 °C, the second temperature T2 is 650-720 °C, and the third temperature T3 is 870-960 °C.

2. The method according to claim 1, characterized in that, The atomic ratio of titanium, cobalt, copper, nickel, and vanadium in the TiCoCuNiV alloy foil is 1.15 - 1.25:1:0.95 - 1.05:0.95 - 1.05:0.75 - 0.

85.

3. The method according to claim 1 or 2, characterized in that, The preparation method of the TiCoCuNiV alloy foil includes: sequentially placing copper, nickel, cobalt, titanium, and vanadium metals in a container, and then conducting vacuum arc melting to obtain a TiCoCuNiV alloy ingot; cutting and polishing the TiCoCuNiV alloy ingot to obtain a TiCoCuNiV alloy foil.

4. The method according to claim 1 or 2, characterized in that, The method further includes: before placing the TiCoCuNiV alloy foil between the TC4 titanium alloy and the TiAl alloy, cutting the TC4 titanium alloy and the TiAl alloy into connecting specimens.

5. The method according to claim 1 or 2, characterized in that, The thickness of the TiCoCuNiV alloy foil is 40 - 60 μm.

6. The method according to claim 1 or 2, characterized in that, The method further includes: cooling the product obtained by the vacuum hot pressing to a fourth temperature T4 at a cooling rate of 2 - 6 °C / min and then cooling it in the furnace, where the fourth temperature T4 is higher than the second temperature T2.

7. The method according to claim 6, characterized in that The fourth temperature T4 is 720 - 750 °C, the first heating rate is 2 - 8 °C / min, the second heating rate is 12 - 18 °C / min, and the third heating rate is 8 - 12 °C / min.

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