CN108262579B - Toughening transition dissimilar material connection joint structure and preparation method - Google Patents

Abstract

The invention relates to a preparation method of a transition joint of titanium, titanium alloy, aluminum and aluminum alloy with a staggered toughened transition structure, in particular to a preparation method of a transition joint of titanium, titanium alloy, aluminum and aluminum alloy. Designing a joint structure, and preparing the transition joint in a grooving powder-adding cladding mode. Aiming at the problem that the titanium aluminum is easy to form brittle intermetallic compounds, the distribution is designed from two aspects of a joint structure and a joint transition material, the prepared toughening transition dissimilar material joint structure can avoid generating continuous brittle phases and can improve the mechanical property of the joint by controlling crack propagation, and the problem that the strength of the titanium aluminum joint is not high is solved.

Description

Toughening transition dissimilar material connection joint structure and preparation method

technical field

The invention relates to the field of dissimilar metal connection, in particular to a method for preparing a transition joint of titanium and titanium alloys with dislocation toughening transition structures and aluminum and aluminum alloys.

Background technique

The composite structure of dissimilar metals is more and more widely used in aerospace, shipbuilding, electric power industry and other fields. Titanium alloys are widely used in aerospace, petrochemical and other fields because of their strong heat resistance, high specific strength, good plasticity, toughness and corrosion resistance. Aluminum and aluminum alloys have become the most widely used non-ferrous metals in the industry due to their low density and high strength, and have been widely used in aviation, automobiles, machinery and other industries. In order to meet the development requirements of lightweight structure, integration of structure and function, and low-cost design and manufacturing, it has been more and more important to combine the performance advantages of different materials and use materials with different characteristics together. Titanium alloys have high specific strength and high temperature resistance, but are relatively expensive. Aluminum alloys have low density and relatively low prices, so when special applications are required, aluminum/titanium composite structures can be used.

In the welding of dissimilar metal materials, due to the different physical and chemical properties of the two materials, some combinations are even very different, which will have a great impact on the welding process. Compared with the welding of the same material, the welding mechanism and operation technology of dissimilar materials are much more complicated than those of the same material.

Majumdar et al. used CO2 laser to weld TC4 and aluminum-magnesium alloys. Many cracks were generated at the welded joints. These cracks were mainly caused by the newly formed intermetallic compounds Ti3Al phase and TiAl phase, and the joint strength was only 33 ~ 57MPa. Later researchers added A layer of Nb plate was added to improve the crack situation, but the joint strength was still low, only 127MPa.

Japanese scholar T.Takemoto et al. studied the brazing of pure titanium and pure aluminum under vacuum conditions of 600-620 °C. The highest strength is only 70MPa.

Li Yajiang, Xu Guoqing and others in my country have done some research on the method of aluminizing titanium plates. This diffusion welding method inhibits the generation of intermetallic compounds to a certain extent, but the tensile strength of welded joints is only 180MPa at the highest.

Wagner of the Institute of Applied Rays in Bremen, Germany, used a Nd:YAG laser to conduct a welding and brazing lap test on Al/Ti. The laser directly acts on the aluminum alloy base metal lapped on the titanium plate by means of heat conduction, and melts The aluminum alloy base metal is brazed to the titanium alloy plate, and the number of intermetallic compounds is controlled by parameters, and the tensile strength reaches 220MPa.

Professor Chen Yanbin of Harbin Institute of Technology in China and others used AlSi12 as the filler material, and the laser directly acts on the filler material to obtain a composite joint with dual characteristics of fusion welding and brazing. The average tensile strength of the double-sided formed weld joint can best reach 278MPa.

Aiming at the shortcomings of laser welding, such as low utilization rate, low welding efficiency and only welding thin plates, Professor Xiao Rongshi of Beijing University of Technology and others adopted the laser deep welding method to obtain better welded joints, and the obtained welded joints were the best. The highest tensile strength is only 217MPa.

Patented a titanium-steel dissimilar metal sintering/welding connection method, which uses titanium or its alloys, V-Cu-based gradient alloy powders C1, C2, C3, and stainless steel one by one in a mold and pre-pressurized, and then The mold is placed in the sintering equipment for spark plasma sintering. The V-Cu-based gradient alloys C1, C2, and C3 are composed of mixed powders with a gradient of expansion coefficients that are mixed with various metal powders in different proportions. Titanium-steel dissimilar Metal sintered/welded joints have higher mechanical properties. This invention also adopts the method of transition joint in the connection of dissimilar metals. Compared with this patent, there is a big difference in structure. It adopts the concept of bionics, and controls the propagation of cracks through the design of bionics.

The problems that still exist in the existing titanium-aluminum connection methods can be summarized as follows:

1. Titanium and titanium alloys and aluminum and aluminum alloy joints produce brittle intermetallic compound layers, and the tensile strength of titanium and titanium alloys and aluminum and aluminum alloy joints is low;

2. The joints of titanium and titanium alloys and aluminum and aluminum alloys produce brittle intermetallic compound layers, and the toughness of the joints is quite different from the toughness of the base metal.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a transition joint adopting a dislocation toughened transition structure and a preparation method thereof.

The following technical solutions are adopted to realize the purpose of the present invention:

A method for preparing a transition joint of titanium and titanium alloys and aluminum and aluminum alloys, comprising the transition from titanium to titanium-aluminum-tin-silicon and then to aluminum-tin-silicon and then to aluminum-silicon and from titanium to titanium- Two transition regions of aluminum-vanadium-silicon;

A method for preparing a transition joint of titanium and titanium alloys with a dislocation toughened transition structure and aluminum and aluminum alloys, the specific steps are as follows:

In step 1, the surface of the titanium and titanium alloy plates is pre-processed, and a hexagonal trough-shaped groove is processed on the surface of the titanium and titanium alloy. °, the depth of the slot is 0.5-2mm, the hexagonal platforms are closely arranged on the surface of the titanium alloy, the upper surfaces of the hexagonal platforms form a symmetrical relationship, and the distance between the edges of the hexagonal platforms is 0.5-1.5mm;

Step 2, grinding and cleaning the slotted titanium and titanium alloy to remove surface oxides and oil stains, etc.;

Step 3, add aluminum-tin-silicon mixed powder to the titanium and titanium alloy grooves after grinding and cleaning, the specific gravity of tin is 30-35%, the specific gravity of silicon is 3-10%, and the remaining amount of aluminum is added until it just fills the cavity. groove;

Step 4, using vacuum electron beam to perform cladding treatment on the added powder;

Step 5, adding aluminum-copper-silicon mixed powder to the groove after the cladding treatment, the specific gravity of tin is 10-15%, the specific gravity of silicon is 1.2-2.7%, and the balance of aluminum;

Step 6, using vacuum electron beam to perform cladding treatment on the added powder;

Step 7: Take a vanadium foil with a thickness of 0.05-1.5 mm, put the vanadium foil on the treated surface, and deduct the area corresponding to the hexagonal table in step 1, and add aluminum-silicon powder to all positions on the surface of the joint. The specific gravity of silicon is 1.2-2.7%, the distance between the upper surface of the powder and the upper surface of the vanadium foil is 0.5mm-1mm;

In step 8, the surface of the transition joint is subjected to cladding treatment with a vacuum electron beam.

Further, in step 1, the specific steps of preparation before welding are as follows: pre-processing the surface of the titanium and titanium alloy plates, and machining a hexagonal trapezoid groove on the surface of the titanium and titanium alloy, and the size of the hexagonal trapezoid is a circumscribed circle diameter of 0.5~ 2mm, the slotting draft angle is 10-30°, the slot depth is 0.5-2mm, the hexagonal platforms are closely arranged on the surface of the titanium alloy, the upper surfaces of the hexagonal platforms form a symmetrical relationship, and the distance between the edges of the hexagonal platforms is 0.5～1.5mm;

Further, in step 2, the slotted titanium and titanium alloy are ground and cleaned to remove oxides and oil stains on the surface of the titanium alloy.

Further, in step 7, take a vanadium foil with a thickness of 0.05-1.5 mm, pad the vanadium foil on the treated surface, deduct the area corresponding to the hexagonal pyramid in step 1, and add aluminum-silicon powder to all positions on the surface of the joint , the specific gravity of silicon is 1.2-2.7%, and the distance between the upper surface of the powder and the upper surface of the vanadium foil is 0.5mm-1mm;

Compared with the prior art, the present invention has the following significant advantages:

1. The present invention adopts the structure of dislocation toughening transition to prepare the transition joint of titanium-aluminum connection, including the transition from titanium to titanium-aluminum-tin-silicon and then to aluminum-tin-silicon and then to aluminum-silicon and from titanium to titanium-aluminum-tin-silicon. Transition to two transition regions of titanium-aluminum-vanadium-silicon, where the intermetallic compounds are optimized separately, reducing the probability of brittle phases.

2. The present invention adopts the dislocation toughening transition structure. When the crack expands to the soft material, the crack needs more energy to achieve the expansion effect, or the expansion direction needs to be changed to increase the energy to support the rapid expansion of brittle fracture cracks. .

Description of drawings

Figure 1 is a partial three-dimensional view of the titanium alloy sheet after processing;

Fig. 2 is a partial top view of the titanium alloy surface after processing in Example 1 and its size information diagram;

3 is a cross-sectional view of a titanium alloy surface hexagonal table groove and its size information diagram after processing in Example 1;

Figure 4 is a partial three-dimensional view of vanadium foil;

Figure 5 is a schematic cross-sectional view of the transition joint cladding structure;

Figure 6 is a binary phase diagram of aluminum, silicon, and tin.

Detailed ways

The technical method of the present invention is not limited to the specific embodiments listed below, but also includes any combination between the specific embodiments.

Example 1

Step 1, the surface of the TC4 titanium alloy plate is pre-processed, and the hexagonal pyramid-shaped groove is processed on the surface of the titanium alloy, as shown in Figure 1. The size of the hexagonal table is the circumscribed circle diameter of 1.5mm, the draft angle of the slot is 15°, and the depth of the slot is 1.5mm. The hexagonal table is closely arranged on the surface of the titanium alloy. The upper surface of the hexagonal table forms a symmetrical relationship. The distance between the table edges is 1.3mm;

Step 2, grinding and cleaning the titanium alloy after slotting to remove oxides and oil stains on the surface of the titanium alloy;

Step 3, adding aluminum-copper mixed powder with a ratio of aluminum-tin-silicon to 62:30:8 into the groove after grinding and cleaning, and adding it to just fill the groove;

Step 4, using vacuum electron beam to perform cladding treatment on the added powder;

Step 5, adding a mixed powder with a ratio of Al-Sn-Si to 83:15:2 to the groove after the cladding treatment;

Step 6, using vacuum electron beam to perform cladding treatment on the added powder;

Step 7: Take a vanadium foil with a thickness of 0.1 mm, place the vanadium foil on the treated surface, and deduct the area corresponding to the hexagonal pyramid in Step 1, as shown in Figure 4. Add aluminum-silicon powder to all positions on the surface of the joint, the specific gravity of silicon is 1.2-2.7%, and the upper surface of the powder is 0.5mm away from the upper surface of the vanadium foil;

Step 8, use vacuum electron beam to clad the surface of the transition joint, and the specific parameters of the vacuum electron beam to clad the added powder are: chamber vacuum 7E-2, gun vacuum 8E-2, beam current 17mA, scanning speed is 10mm/s.

The surface size information of the prepared titanium alloy after processing is shown in Figures 2 and 3.

The invention includes two transition regions from titanium to titanium-aluminum-tin-silicon and then to aluminum-tin-silicon and then to aluminum-silicon and from titanium to titanium-aluminum-vanadium-silicon, and cracks can be effectively controlled by this soft and hard alternating structure The material in the soft zone has better toughness, while the material in the hard zone is more brittle. The crack will be generated from the brittle region and will be terminated when it expands to the ductile region. Therefore, if the crack wants to continue to expand, it needs higher energy input, so the present invention starts from Controlling the angle of crack propagation improves the tensile strength and toughness of the joint. The cross-section of the transition joint cladding structure is shown in Figure 5.

The present invention adds silicon element and tin element to the transition joint.

The addition of silicon can effectively suppress the thickness of the intermetallic compounds at the interface. The silicon in TiAl3 has a strong binding ability with titanium, which restricts the movement of titanium in TiAl3, resulting in a large diffusion activation energy and a very slow growth of the reaction layer. Slow, and when the silicon content reaches a certain value, it even reacts with TiAl3 to form other compounds;

Tin is a neutral element for titanium and titanium alloys. This element is added to titanium and titanium alloys to improve the corrosion resistance of titanium and titanium alloys. The room temperature tensile strength, high temperature tensile properties and resistivity of titanium and titanium alloys, and tin has strong metal properties, the first molten tin easily reacts with titanium, reducing the probability of the formation of intermetallic compounds between titanium and aluminum, so that The intermetallic compound in the joint has a certain plasticity; in addition, in α titanium, tin and aluminum can also play a role in stabilizing the α phase together, and the content of tin is high, and a large superelastic strain can be obtained, as shown in Figure 6.

When tin and aluminum are liquid, they can dissolve each other in a wide range of components, but the solid solubility of tin in aluminum is very small (<0.01%), tin and aluminum do not form compounds, and tin exists in free state with aluminum;

The crystalline phase structure of Al-T-Si is composed of α-aluminum, Si, and β-tin phases. The β-tin phase adheres to the eutectic Si and solidifies and is distributed in the grain boundary in a near network. crystalline" phase structure.

Claims (5)

1. A toughening transition dissimilar material connecting joint structure is characterized in that the structure is as follows: the transition joint of the TC4 titanium alloy and the aluminum alloy comprises the following specific preparation steps:

step 1, performing surface preprocessing on a titanium or titanium alloy plate, and processing a hexagonal frustum groove on the surface of the titanium or titanium alloy, wherein the size of the hexagonal frustum groove is that the diameter of a circumscribed circle is 0.5-2 mm, the angle of a slotting and drawing die is 10-30 degrees, and the depth of a slotted hole is 0.5-2 mm;

step 2, carrying out impurity removal pretreatment on the slotted titanium or titanium alloy plate;

step 3, adding aluminum-tin-silicon mixed powder into the groove of the titanium or titanium alloy plate after polishing and cleaning, wherein the specific gravity of tin is 30-35%, the specific gravity of silicon is 3-10%, and the balance of aluminum is added until the groove is just filled;

step 4, carrying out cladding treatment on the added powder by adopting a vacuum electron beam;

step 5, adding aluminum-tin-silicon mixed powder into the groove subjected to cladding treatment, wherein the specific gravity of tin is 10-15%, the specific gravity of silicon is 1.2-2.7%, and the balance is aluminum;

step 6, carrying out cladding treatment on the added powder by adopting a vacuum electron beam;

step 7, taking a vanadium foil sheet with the thickness of 0.05-1.5 mm, padding the vanadium foil sheet on the treated surface, and removing the vanadium foil sheet corresponding to the position of the corresponding hexagonal frustum groove on the titanium or titanium alloy plate; placing the vanadium foil on the surface of the titanium or titanium alloy plate; adding aluminum-silicon powder to the surface of the vanadium foil until the position of a hexagonal frustum groove corresponding to the vanadium foil is filled, wherein the distance between the upper surface of the powder and the upper surface of the vanadium foil is 0.5-1 mm, and the proportion of silicon in the aluminum-silicon powder is 1.2-2.7%;

and 8, carrying out cladding treatment on the surface of the transition joint by adopting a vacuum electron beam to complete the preparation of the joint.

2. The structure of the toughened transitional dissimilar material joint connection of claim 1, wherein in step 1, the number of the hexagonal frustum grooves is at least 1, the hexagonal frustum groove groups are formed on the surface of the titanium or titanium alloy plate, two adjacent hexagonal frustum upper surfaces form a symmetrical relationship, and the distance between the adjacent hexagonal frustum edges is 0.5 to 1.5 mm.

3. The toughened transitional dissimilar material joint construction of claim 1, wherein in step 2, the decontamination pretreatment comprises: and polishing and cleaning the grooved titanium or titanium alloy plate to remove oxides and oil stains on the surface of the titanium or titanium alloy plate.

4. The toughening transition dissimilar material joint structure of claim 1, wherein in steps 4, 6 and 8, the specific parameters of the vacuum electron beam cladding treatment of the added powder are as follows: chamber vacuum 7E^-2Gun vacuum 8E^-2The beam current range is 15-21mA, and the scanning speed is 7-12 mm/s.

5. The method of making a toughened transitional dissimilar material joint construction of any one of claims 1-4.

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