CN114012234B - Vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy - Google Patents

Abstract

The invention discloses a vacuum diffusion welding method for dissimilar metals of a titanium alloy and a magnesium alloy. By adding a certain amount of Mn element to the magnesium alloy, TiMn and other phases are formed with Ti on the diffusion interface of the magnesium alloy and the titanium alloy to play a role in bonding. The role of the transition layer solves the problem that Mg-Ti atoms are neither miscible nor produce compound phases. The surface to be welded in the present invention is selected to be perpendicular to the deformation direction of the magnesium alloy, and the Mg-RE reinforcement phase in the alloy is stretched along the metal flow direction to form a fiber-like distribution, and the reinforcement near the diffusion interface is riveted into the diffusion transition layer as tightly as a rivet. Increase the connection strength between the magnesium alloy and the diffusion transition layer. The vacuum diffusion welding method of the present invention has good welding quality, its tensile strength is as high as 324.15MPa, its elongation is 4.7%, and its shear strength is 121.77MPa. The obtained alloy welded joint has high bonding strength and can be widely used in magnesium alloy and titanium Welding between alloys.

Description

A vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy

technical field

The invention belongs to the field of metal material welding, and relates to a vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy.

Background technique

The lightweight development of weaponry and aerospace equipment is a major strategic requirement for national security. The application of lightweight structural parts can not only improve the payload and maneuverability of flight equipment and weaponry, but also produce objective technical and economic benefits. Titanium alloy has the advantages of high strength, good corrosion resistance and heat resistance. Magnesium alloys have the advantages of low density, high specific strength, and good damping and shock absorption effects, and have great application potential in the aerospace field. Titanium alloy and magnesium alloy play an important role in the lightweight manufacturing of weaponry and aerospace equipment. At present, in the assembly process of weaponry and aerospace equipment, titanium alloy structural parts and magnesium alloy structural parts are mainly connected by bolts. It is necessary to open holes, overlap each other or add auxiliary connecting plates, which not only weakens the section of the member but also increases the complexity of the structure, without taking advantage of the reliability and light weight of the structure. The preparation of titanium/magnesium dissimilar metal integrated (integral) structural parts can solve the above problems. The key stress-bearing parts of the structural parts are made of titanium alloy, and the non-critical parts are made of magnesium alloy, so that the titanium/magnesium dissimilar metal integrated (integral) structural parts It can not only meet the use requirements, but also realize further lightening of the structural parts.

Due to the large difference in physical and chemical properties between magnesium alloys and titanium alloys, especially the melting point of titanium is almost three times that of magnesium, fusion welding cannot be used to achieve a reliable connection between magnesium alloys and titanium alloys. At the same time, the two elements Mg and Ti are immiscible in the liquid phase and the solid phase state, and cannot form a compound phase, which cannot meet the basic conditions of diffusion welding. In addition, the main strengthening forms of wrought magnesium alloys are fine grain strengthening and work hardening. If the welding temperature is too high, the grains of the magnesium alloy base metal will grow seriously during the welding process, which will affect the connection performance of the welded joint. Therefore, it is difficult to achieve reliable connection between magnesium alloy and titanium alloy by direct contact diffusion welding. At present, the diffusion welding methods of magnesium alloy and titanium alloy disclosed in the prior art mostly use aluminum foil as the intermediate layer to weld magnesium alloy and titanium alloy. However, during the processing process, aluminum foil and magnesium alloy will undergo eutectic reaction at welding temperature to form hard and brittle phase Mg. ₁₇ Al ₁₂ , the appearance of the hard and brittle metal compound Mg ₁₇ Al ₁₂ phase is not conducive to obtaining excellent and stable welded joints. Therefore, it is very important to explore a welding method for dissimilar metals of titanium alloy and magnesium alloy to achieve high-strength connection between the two.

Contents of the invention

In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy, which can improve the mechanical properties of the welded joint of titanium alloy and magnesium alloy.

One of purpose of the present invention adopts following technical scheme to realize:

A vacuum diffusion welding method for titanium alloy and magnesium alloy dissimilar metals, comprising the following steps:

(1) grinding, cleaning and drying the titanium alloy sample and the magnesium alloy sample to be welded;

(2) Place the titanium alloy sample treated in step (1) and the magnesium alloy sample on the surface to be welded in the mold, then place the mold between the upper and lower pressure heads of the hot-press furnace, close the hot-press furnace and evacuate ;

(3) Apply pre-pressure to the sample to be welded in step (2), heat up to the set temperature, increase the pressure to the welding pressure and enter the heat preservation and pressure holding stage; after the end, release the pressure and cool down, take out the mold, and obtain titanium alloy and magnesium alloy welded composite structures.

Further, the heating rate in the step (3) is 5-10°C/min, and the set temperature is 430-520°C.

Further, in the step (3), the pre-pressure is 1-10 MPa, the welding pressure is 10-30 MPa, and the heat preservation and pressure holding time is 30-180 min.

Further, the cooling process in the step (3) is to lower the temperature to below 100° C. at a rate of 1-5° C./min.

Further, the degree of vacuum in the step (2) is below 5×10 ^-1 Pa.

Further, the roughness of the step (1) polished is 0.8-3 μm.

Further, the magnesium alloy is a plastically deformed Mg-RE-X-Mn alloy, wherein the Mn element content accounts for 0.5-1.5%wt of the alloy; RE is selected from one to three of Y, Gd, Ce, Nd, and Sc. The element content of RE is 3 to 8 times that of Mn; X is selected from one or both of Zn and Zr, and X represents that the element content is 0.5 to 2 times that of Mn.

Further, the preparation of the magnesium alloy sample includes the following steps: performing solution treatment on the Mg-RE-X-Mn alloy, the process is firstly keeping the temperature at 500-520°C for 8-12 hours, and then keeping the temperature at 400-420°C for 6 hours. ～10h, water quenching in hot water at 80～100℃; heat the Mg-RE-X-Mn alloy after solution treatment to 420～440℃ and keep it for 30min, then forge, extrude or roll to obtain deformed Mg-RE -X-Mn alloy.

Further, the surface to be welded in the step (1) is selected perpendicular to the deformation direction of the magnesium alloy.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a vacuum diffusion welding method for dissimilar metals of a titanium alloy and a magnesium alloy. By adding a certain amount of Mn element to the magnesium alloy, phases such as TiMn and Ti ₂ Mn are formed with Ti on the diffusion interface between the magnesium alloy and the titanium alloy. , which plays the role of connecting the transition layer, and solves the problem that the Mg-Ti atoms are neither miscible nor produce a compound phase. The surface to be welded in the present invention is selected to be perpendicular to the deformation direction of the magnesium alloy, the Mg-RE reinforcement phase in the alloy is stretched along the metal flow direction and distributed in a fiber shape, and the Mg-RE reinforcement near the diffusion interface is riveted and diffused tightly like a rivet The transition layer increases the connection strength between the magnesium alloy and the diffusion transition layer. When welding the sample, the present invention uses a mold to fix the sample to be welded, which can suppress the thermal expansion and deformation of the magnesium alloy, reduce the difference in thermal expansion size between the magnesium alloy and the titanium alloy, and help to eliminate the interface welding stress; the thermal insulation during the welding process of the present invention After holding the pressure, the sample is cooled with a small cooling rate, which reduces the thermal stress caused by uneven thermal expansion and contraction, and improves the mechanical properties of the titanium alloy and magnesium alloy welded joints. The vacuum diffusion welding method of the present invention has good welding quality and high bonding strength of alloy welded joints, and can be widely used in welding between magnesium alloys and titanium alloys.

Description of drawings

Fig. 1 is the assembly structure schematic diagram that titanium alloy and magnesium alloy diffusion welding are used in the embodiment 1-13 of the present invention;

Fig. 2 is a metallographic structure diagram of a welded joint in Example 3 of the present invention;

3 is a TEM element distribution diagram of the diffusion interface of Example 3 of the present invention;

Fig. 4 is the scanning electron microscope picture of the welding joint of embodiment 3 of the present invention;

Fig. 5 is the welded joint tensile test pattern drawing of the present invention: wherein 1# is the sample to be tensile tested by the welded joint of Example 3, 2# is the finished sample of the welded joint tensile test of Example 3, and 3# is the sample of Example 10 Completed sample of welded joint tensile test;

Fig. 6 is a scanning electron microscope topography diagram of a tensile fracture of a welded joint in Example 3 of the present invention;

In the figure: 1. Upper pressure head; 2. Magnesium alloy; 3. Titanium alloy; 4. Lower gasket; 5. Upper pressure column; 6. Upper gasket; 7. Mold cover; 8. Lower pressure column; 9. Head down.

detailed description

Below, the present invention will be further described in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of not conflicting, the various embodiments described below or the technical features can be combined arbitrarily to form new embodiments. .

Example 1

A vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy, comprising the following steps;

(1) Pretreatment of the surface to be welded: use sandpaper to treat TC4 titanium alloy and Mg-7Gd-4Y-1Zn-1Mn magnesium alloy (the mass ratio of Gd, Y, Zn, and Mn is 7:4:1:1, and the Mn element Accounting for alloy 1%wt) the surface to be welded is polished, the surface to be welded of the magnesium alloy is selected perpendicular to the deformation direction of the magnesium alloy, the roughness Ra of the surface to be welded of the titanium alloy and the magnesium alloy is about 1.8 μm after grinding, and then the surface to be welded Soak the surface in alcohol for ultrasonic cleaning for 5 minutes, and then dry it with cold air to remove the oil and impurity particles remaining on the surface to be welded.

(2) Stack the titanium alloy and magnesium alloy surfaces to be welded neatly after the step of cleaning the surface of the sample to be welded, assemble the stacked sample in a high-temperature alloy mold, and spray carbonization on the contact part of the mold cavity and the sample Boron coating to facilitate removal of the specimen after welding (as shown in Figure 1). Place the mold equipped with the welding sample in the middle of the upper and lower indenters of the vacuum hot-press furnace, keep the axial alignment between the mold and the indenter, close the vacuum hot-press furnace door and evacuate to below 5×10 ^-1 Pa, pass the vacuum The pressure head on the furnace applies a pre-pressure of 10MPa to the sample to be welded, the heating rate is 10°C/min to the welding temperature of 460°C, the welding pressure is adjusted to 20MPa, and the heat preservation and pressure are kept for 120 minutes. °C/min and slowly cooled to below 100 °C to take out the mold to obtain a welded composite structure of TC4 titanium alloy and Mg-7Gd-4Y-1Zn-1Mn magnesium alloy.

Example 2

The difference between embodiment 2 and embodiment 1 is that step (1) TC4 titanium alloy is adjusted to TA2 titanium alloy, and the rest is the same as embodiment 1.

Example 3

The difference between embodiment 3 and embodiment 1 is: step (1) Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-7Gd-4Y-1Zn-0.1Mn magnesium alloy (Gd, Y, Zn, Mn The mass ratio is 7:4:1:0.1, wherein the Mn element accounts for 0.1% of the alloy), the welding temperature in step (2) is adjusted to 490° C., and the rest are the same as in Example 1.

Example 4

The difference between embodiment 4 and embodiment 1 is: step (1) Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-7Gd-4Y-1Zn-0.5Mn magnesium alloy (Gd, Y, Zn, Mn The mass ratio is 7:4:1:0.5, wherein the Mn element accounts for 0.5%wt of the alloy, the welding temperature in step (2) is adjusted to 490° C., and the rest are the same as in Example 1.

Example 5

The difference between embodiment 5 and embodiment 1 is that the welding temperature in step (2) is adjusted to 490° C., and the rest is the same as embodiment 1.

Example 6

The difference between embodiment 6 and embodiment 1 is: step (1) Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-7Gd-4Y-1Zn-1.5Mn magnesium alloy (Gd, Y, Zn, Mn The mass ratio is 7:4:1:1.5, wherein the Mn element accounts for 1.5%wt of the alloy, the welding temperature in step (2) is adjusted to 490° C., and the rest are the same as in Example 1.

Example 7

The difference between embodiment 7 and embodiment 1 is: step (1) Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-8Gd-3Y-0.5Zr-1Mn magnesium alloy (Gd, Y, Zr, Mn The mass ratio is 8:3:0.5:1, wherein the Mn element accounts for 1%wt of the alloy, the welding temperature in step (2) is adjusted to 490° C., and the rest are the same as in Example 1.

Example 8

The difference between embodiment 8 and embodiment 1 is that step (1) TC4 titanium alloy is adjusted to TA2 titanium alloy, step (2) welding temperature is adjusted to 490° C., and the rest are the same as embodiment 1.

Example 9

The difference between embodiment 9 and embodiment 1 is that step (1) TC4 titanium alloy is adjusted to TA2 titanium alloy, and Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-8Gd-3Y-0.5Zr-1Mn magnesium alloy (The mass ratio of Gd, Y, Zr, and Mn is 8:3:0.5:1, wherein the Mn element accounts for 1%wt of the alloy), the welding temperature in step (2) is adjusted to 490°C, and the rest are the same as in Example 1.

Example 10

The difference between embodiment 10 and embodiment 1 is that the welding temperature in step (2) is adjusted to 520° C., and the rest is the same as embodiment 1.

Example 11

The difference between Example 11 and Example 1 is that step (1) Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-8Gd-3Y-0.5Zr-1Mn magnesium alloy (Gd, Y, Zr, Mn The mass ratio is 8:3:0.5:1, wherein the Mn element accounts for 1%wt of the alloy, the welding temperature in step (2) is adjusted to 520°C, and the rest are the same as in Example 1.

Example 12

The difference between embodiment 12 and embodiment 1 is that step (1) TC4 titanium alloy is adjusted to TA2 titanium alloy, the welding temperature of step (2) is adjusted to 520° C., and the rest are the same as embodiment 1.

Example 13

The difference between Example 13 and Example 1 is that step (1) TC4 titanium alloy is adjusted to TA2 titanium alloy, and Mg-7Gd-4Y-1Zn-1Mn magnesium alloy is adjusted to Mg-8Gd-3Y-0.5Zr-1Mn magnesium alloy (The mass ratio of Gd, Y, Zr, and Mn is 8:3:0.5:1, wherein the Mn element accounts for 1%wt of the alloy), the welding temperature in step (2) is adjusted to 520°C, and the rest are the same as in Example 1.

Comparative example 1

The difference between Comparative Example 1 and Example 1 is that the titanium alloy (TC4) and the magnesium alloy (AZ31B) to be welded in step (2) are neatly stacked and adjusted to use aluminum foil as the middle layer, and the aluminum foil is placed between the magnesium alloy and the magnesium alloy. Between the titanium alloys, they are stacked and assembled in the superalloy mold. All the other are identical with embodiment 1.

Experimental example 1

Mechanical Properties Test of Titanium Alloy/Magnesium Alloy Welded Joint

The welded joints of the titanium alloy/magnesium alloy welded composite structural parts obtained in Examples 1 to 13 of the present invention are subjected to performance tests, and the test process refers to the national standard (GB/T228.1-2010, tensile test of metal materials: room temperature test method). The results are shown in Table 1.

Table 1

It can be seen from Table 1 that the welded joints of titanium/magnesium alloy welded composite structural parts obtained in Examples 1 to 13 of the present invention have good mechanical properties, wherein the tensile strength is as high as 258.07-324.15MPa, the elongation is 2.1%-9.1%, and the tensile strength is as high as 258.07-324.15MPa. The shear strength reaches 88.3-121.77MPa. In Comparative Example 1, aluminum foil is used as the diffusion intermediate layer for welding. Compared with Example 1, the mechanical properties of the welded joint obtained are weaker. It shows that the welding joint between titanium alloy and magnesium alloy obtained by the method of the present invention has higher bonding strength.

Fig. 2 is the metallographic structure diagram of the welded joint of embodiment 3 of the present invention, Fig. 3, 4 are respectively the TEM element distribution diagram of the diffusion interface of the embodiment 3 of the present invention, the scanning electron microscope structure diagram of the welded joint, it can be seen from the figure that the present invention passes Adding Mn element to the magnesium alloy enriches and forms TiMn, Ti ₂ Mn and other phases with Ti at the welding interface, which plays the role of connecting the transition layer, and solves the problem that Mg-Ti atoms are neither miscible nor can form a compound phase, and realize Reliable connection between titanium alloy and magnesium alloy; at the same time, the magnesium alloy treated by plastic processing makes the Mg-RE strengthening phase in the magnesium alloy stretch along the metal flow direction and distribute in fiber form, forming a state perpendicular to the welding interface, Mg-RE strengthening The end close to the diffusion interface is tightly riveted into the diffusion transition layer like a rivet, and the other end penetrates into the magnesium alloy and is closely combined with the magnesium alloy, which increases the connection strength between the magnesium alloy and the diffusion transition layer, and obtains a high-strength titanium alloy and magnesium alloy. Metal welded joints. Figures 5 and 6 are the sample drawing of the tensile test of the welded joint and the scanning electron microscope image of the tensile fracture of the welded joint in Example 3, respectively.

The welding method of the present invention is used for welding, and the result shows that temperature has a great influence on the welding joint. When the temperature is low, the diffusion of Mn element is insufficient, and the connection performance of the transition layer formed at the welding interface is poor. When the welded joint is subjected to a tensile test, fracture will occur at the welding interface, and the tensile strength is about that of the magnesium alloy base material. 88%, low elongation at break. When the welding temperature rises to 490°C, more Mn elements are enriched at the welding interface, and the formed TiMn transition layer has higher connection strength. The tensile strength of the welded joint is close to the strength of the magnesium alloy base material, and the fracture is still at the welding interface. place. However, there are a large number of tear bands in the fracture morphology. When the welding temperature is increased to 520°C, the tensile strength of the welded joint is the strength of the magnesium alloy base material, and tensile fracture occurs on the magnesium alloy base material, which is due to the growth of the magnesium alloy grain and the strengthening phase Coarsening leads to a decrease in the properties of the magnesium alloy base material.

In the present invention, the titanium alloy and the magnesium alloy are stacked and assembled into the superalloy mould. The constraint of the mold can restrict the thermal expansion size of the magnesium alloy, reduce the difference in the thermal expansion size of the magnesium alloy and the titanium alloy, help to eliminate the interface welding stress, and improve the titanium alloy and titanium alloy. Mechanical properties of magnesium alloy welded joints. And because the expansion coefficients of magnesium alloys and titanium alloys are different, the present invention adopts a slower cooling rate, which reduces the thermal stress caused by uneven thermal expansion and contraction, and is different from the superalloys with higher thermal stability and rigidity during the addition process. The reliability of the welded joint between magnesium alloy and titanium alloy is realized under the cooperation of the degree of thermal expansion of magnesium alloy constrained by the mold.

The above-mentioned embodiment is only a preferred embodiment of the present invention, and cannot be used to limit the protection scope of the present invention. Any insubstantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of the present invention. Scope of protection claimed.

Claims (8)

1. a vacuum diffusion welding method of titanium alloy and magnesium alloy dissimilar metal, is characterized in that, comprises the following steps: (1) Grinding, cleaning and drying the titanium alloy sample and the magnesium alloy sample to be welded; (2) Place the titanium alloy sample treated in step (1) and the magnesium alloy sample on the surface to be welded in the mold, then place the mold between the upper and lower pressure heads of the hot-press furnace, close the hot-press furnace and vacuumize ; (3) Apply pre-pressure to the sample to be welded in step (2), raise the temperature to the set temperature, increase the pressure to the welding pressure and enter the heat preservation and pressure holding stage; after the end, release the pressure and lower the temperature, take out the mold, and obtain titanium alloy and magnesium Alloy welded composite structural parts; The magnesium alloy is a plastically deformed Mg-RE-X-Mn alloy, wherein the Mn element content accounts for 0.5-1.5% wt of the alloy; RE is selected from one to three of Y, Gd, Ce, Nd, and Sc, The RE element content is 3~8 times of the Mn element content; X is selected from one or both of Zn and Zr, and the X represents element content is 0.5~2 times of the Mn element content. 2. The vacuum diffusion welding method of dissimilar metals of titanium alloy and magnesium alloy as claimed in claim 1, characterized in that the heating rate in the step (3) is 5-10°C/min, and the set temperature is 430-520°C . 3. The vacuum diffusion welding method of titanium alloy and magnesium alloy dissimilar metals as claimed in claim 1, characterized in that, the step (3) pre-pressure is 1-10MPa, the welding pressure is 10-30MPa, and the heat preservation and pressure holding time 30~180min. 4 . The vacuum diffusion welding method of dissimilar metals of titanium alloy and magnesium alloy according to claim 1 , wherein the cooling process in the step (3) is to lower the temperature to below 100° C. at a rate of 1-5° C./min. 5 . The vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy according to claim 1 , wherein the degree of vacuum in the step (2) is below 5×10 ⁻¹ Pa. 6 . The vacuum diffusion welding method for dissimilar metals of titanium alloy and magnesium alloy according to claim 1 , wherein the roughness of grinding in the step (1) is 0.8-3 μm. 7. the vacuum diffusion welding method of titanium alloy and magnesium alloy dissimilar metals as claimed in claim 1, is characterized in that, the preparation of described magnesium alloy sample comprises the following steps: carry out solid solution to Mg-RE-X-Mn alloy Treatment, the process is firstly holding at 500~520°C for 8~12h, then holding at 400~420°C for 6~10h, and quenching in hot water at 80~100°C; for the Mg-RE-X-Mn alloy after solid solution treatment Heating to 420~440°C for 30min and then forging, extruding or rolling to obtain deformed Mg-RE-X-Mn alloy. 8. The vacuum diffusion welding method of dissimilar metals of titanium alloy and magnesium alloy as claimed in claim 1, characterized in that the surface to be welded in the step (1) is selected perpendicular to the deformation direction of the magnesium alloy.

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