Titanium / titanium alloy surface modification method and titanium-magnesium dissimilar metal ultrasonic-assisted brazing method

Abstract

The invention discloses a titanium / titanium alloy surface modification method and an ultrasonic-assisted brazing method for titanium-magnesium dissimilar metal, and belongs to the technical field of brazing. The titanium / titanium alloy surface modification method comprises the steps that after titanium / titanium alloy surface treatment is conducted, a tin layer or a zinc layer is hot-dipped in an ultrasonic-assisted mode. The ultrasonic-assisted brazing method for the titanium-magnesium dissimilar metal comprises the following steps: S1, fixing a magnesium / magnesium alloy subjected to surface treatment, a tin-zinc eutectic alloy intermediate layer and a titanium / titanium alloy together; and S2, ultrasonic-assisted brazing is carried out at the pressure of 0.05-0.2 MPa and the temperature of 200-500 DEG C, and the titanium-magnesium dissimilar metal joint is obtained. The low-temperature connection of the titanium alloy / magnesium alloy dissimilar joint in the atmospheric environment is realized by modifying the surface of the titanium alloy and utilizing an ultrasonic-assisted brazing method. And the shear strength of the titanium-magnesium alloy joint can reach 48.0 MPa.

Description

Technical Field

[0001] The invention relates to the technical field of brazing, in particular to a titanium / titanium alloy surface modification method and a titanium-magnesium dissimilar metal ultrasonic-assisted brazing method. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Magnesium alloys are widely used in aerospace, automotive industry, electronic products and medical machinery due to their low density, high specific strength and rigidity, good damping, thermal conductivity and strong shock absorption. However, the application of magnesium alloys is limited due to their deficiencies in oxidation resistance, corrosion resistance and room temperature plasticity. Titanium alloys are widely used in aerospace, medical, automotive and sporting goods due to their high strength, low density, good corrosion resistance and high temperature performance. However, the application of titanium alloys is limited due to their poor machinability and high cost. Combining these two materials to make composite components can optimize their properties. Therefore, achieving reliable connection between titanium alloys and magnesium alloys has important research significance and application prospects.

[0004] Due to the great difference in the physical and chemical properties between magnesium alloys and titanium alloys, and the large difference in the melting points between titanium alloys and magnesium alloys, it is difficult to simultaneously control the melting state of both during welding, which affects the metallurgical effect and makes it impossible to achieve effective connection between magnesium alloys and titanium alloys by fusion welding. Moreover, the Ti and Mg elements are not mutually soluble in the liquid and solid phases, and no new phases are generated, which cannot meet the welding conditions. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a titanium / titanium alloy surface modification method and a titanium-magnesium dissimilar metal ultrasonic-assisted brazing method. By modifying the titanium alloy surface and selecting a suitable intermediate layer for brazing, ultrasonic assistance is applied during the surface modification and brazing processes respectively, so as to achieve low-temperature connection of magnesium alloy and titanium alloy dissimilar metal joints in atmospheric environment.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In the first aspect, a titanium / titanium alloy surface modification method comprises: ultrasonically assisted hot-dip plating of a tin layer or a zinc layer after surface treatment of the titanium / titanium alloy; the ultrasonically assisted hot-dip plating method comprises: immersing the surface treated titanium / titanium alloy in molten tin or zinc for 3 to 5 minutes, and applying ultrasound to the molten tin or zinc during the insulation period.

[0008] Optionally, the titanium / titanium alloy is selected from one of TC4 titanium, TC6 titanium and TA1 titanium.

[0009] Optionally, surface preparation methods include grinding, pickling, cleaning and drying.

[0010] Optionally, the raw material of the tin layer is one of simple tin, Sn-xZn and Sn-ySb; wherein 0%<x≤30%, 0%<y≤50%.

[0011] Optionally, the raw material of the zinc layer is one of zinc element, Zn-xAl and ZnAlCu system; wherein 0%<x≤30%.

[0012] Optionally, the thickness of the tin-plated layer is 10.50 to 12.50 μm.

[0013] Optionally, the thickness of the zinc coating is 17.02 to 27.35 μm.

[0014] Optional, vibration frequency: 20~30KHz; amplitude: 7~13μm.

[0015] In a second aspect, a method for ultrasonically assisted brazing of titanium-magnesium dissimilar metals comprises the steps of:

[0016] S1, fixing the surface-treated magnesium / magnesium alloy, the tin-zinc eutectic alloy intermediate layer and the titanium / titanium alloy together;

[0017] S2. Perform ultrasonic assisted brazing at a pressure of 0.05 to 0.2 MPa and a temperature of 200 to 500° C. to obtain a titanium-magnesium dissimilar metal joint.

[0018] Optionally, in S1, the magnesium / magnesium alloy is selected from one of AZ31 magnesium alloy, AZ31B magnesium alloy and AM60B magnesium alloy.

[0019] Optionally, in S1, the tin-zinc eutectic alloy intermediate layer is Sn-9Zn foil with a thickness of 20 to 100 μm.

[0020] Optionally, in S2, the temperature is raised to a set temperature and then kept at that temperature for 5 to 8 minutes, and then ultrasonic treatment is performed at the same temperature with a vibration frequency of 30 to 40 kHz and an amplitude of 8 to 12 μm.

[0021] Optionally, the ultrasonic treatment time is 2 to 11 s; specifically 2 s, 5 s, 8 s or 11 s.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention realizes low-temperature connection of titanium alloy / magnesium alloy dissimilar joints under atmospheric environment by modifying the surface of titanium alloy and using ultrasonic assisted diffusion welding method. Ultrasonic assistance in the surface modification process of titanium / titanium alloy can regulate the physical phase and thickness of the coating on the surface of titanium alloy. When zinc coating is selected, a uniform TiZn3, TiZn3+TiZn16+η-Zn and / or η-Zn coating is formed on the surface of titanium alloy, wherein the thickness of TiZn3, TiZn3+TiZn16+η-Zn layer is about 18.31-22.35μm; when tin coating is selected, a Ti2Sn3 and / or β-Sn coating is formed on the surface of titanium alloy, wherein the thickness of Ti2Sn3 is about 0.54-1.42μm. In the ultrasonic assisted brazing process, the brazing seam forming quality, microstructure and performance can be controlled by ultrasonic regulation, thereby obtaining high-quality dissimilar metal joints. When zinc-plated titanium alloy is connected to magnesium alloy, the brazing seam is composed of TiZn3, TiZn3+TiZn16, η-Zn, β-Sn+η-Zn and Mg2Sn; when tin-plated titanium alloy is connected to magnesium alloy, the brazing seam is composed of Ti2Sn3 and β-Sn. The morphology of Mg2Sn is regulated by adjusting the brazing temperature and ultrasonic time to improve the mechanical properties of the joint. The shear strength of the titanium-magnesium alloy joint can reach 48.0MPa. And no vacuum environment is required, which greatly improves the convenience of the brazing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] In order to show the positions of various parts, the distances or sizes between them are exaggerated in the figure, and the schematic diagram is for illustration only.

[0026] Figure 1 This is a schematic diagram of tin plating on the surface of TC4 in Example 1 of the present invention.

[0027] Figure 2 This is a scanning electron microscope image of the tin-plated surface of TC4 in Example 1 of the present invention.

[0028] Figure 3 TEM images of the tin-plated surface of TC4 in Example 1 of the present invention, wherein (a) is a high-resolution dark field image of the TiSn3 region, and (b) is a diffraction spot of the TiSn3 region after a first FFT transformation.

[0029] Figure 4 This is a schematic diagram of TC4 surface galvanizing in Example 2 of the present invention.

[0030] Figure 5 This is a scanning electron microscope image of the zinc-plated surface of TC4 in Example 2 of the present invention.

[0031] Figure 6 This is the TEM image of the zinc-plated surface of TC4 in Example 2 of the present invention.

[0032] Figure 7 This is a schematic diagram of the TC4 / AZ31 welding joint in Example 3 of the present invention.

[0033] Figure 8 These are scanning electron microscope images of the TC4 / AZ31B heterogeneous metal ultrasonic-assisted brazing joints in Example 3 of the present invention, wherein (a) is the microstructure morphology of the joint after 2s of ultrasound, (b) is the microstructure morphology of the joint after 5s of ultrasound, (c) is the microstructure morphology of the joint after 8s of ultrasound, and (d) is the microstructure morphology of the joint after 11s of ultrasound.

[0034] Fig. 9 This is a statistical diagram of the shear strength of the TC4 / AZ31B joint in Example 3 of the present invention.

[0035] Fig.10 This is a schematic diagram of TC4 / AZ31 welding in Example 4 of the present invention.

[0036] Fig.11 These are scanning electron microscope images of the TC4 / AZ31B heterogeneous metal ultrasonic-assisted brazing joints in Example 4 of the present invention, wherein (a) is the microstructure morphology of the joint after 2s of ultrasound, (b) is the microstructure morphology of the joint after 5s of ultrasound, (c) is the microstructure morphology of the joint after 8s of ultrasound, and (d) is the microstructure morphology of the joint after 11s of ultrasound.

[0037] Fig.12 It is the shear strength of TC4 / AZ31 joint in Example 4 of the present invention. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] A titanium / titanium alloy surface modification method comprises: treating the titanium / titanium alloy surface and then ultrasonically assisting hot-dip plating of a tin layer or a zinc layer; the ultrasonically assisted hot-dip plating method comprises: immersing the surface-treated titanium / titanium alloy into molten tin or zinc material and keeping the temperature for 3 to 5 minutes, and applying ultrasonic waves to the molten tin or zinc material during the heat preservation; specifically, the tin or zinc material is melted at 500 to 600° C. and kept the temperature for 20 to 30 minutes, then immersing the surface-modified titanium / titanium alloy into molten metal to maintain the temperature and apply ultrasonic waves, and taking out and cooling naturally after 3 to 5 minutes.

[0041] In the above process, ultrasonic assistance can regulate the physical phase and thickness of the coating on the surface of the titanium alloy, and promote the sufficient flow and diffusion and dissolution of zinc liquid / tin liquid on the surface of the titanium alloy through acoustic streaming and cavitation effects, so as to obtain (Ti2Sn3+β-Sn) coating or (TiZn3, TiZn3+TiZn16+η-Zn, η-Zn) coating, thereby improving the brazing properties of the titanium alloy; the modified titanium / titanium alloy can be used for brazing of dissimilar metal joints with the participation of a tin-zinc eutectic alloy intermediate layer.

[0042] Optionally, the surface treatment method includes grinding, pickling, cleaning and drying; specifically, including: grinding with 180-1200# sandpaper to remove the oxide film on the surface; then soaking in a mixed reagent (HF 15ml, HNO3 60ml, H2O 225ml) for 3-5 minutes to remove the residual oxide film; after rinsing with water, grinding with 2000-2400# sandpaper, and then ultrasonic cleaning with acetone or ethanol for 3-5 minutes to remove oil stains on the surface; then storing in ethanol and drying with cold air before use.

[0043] Optionally, the titanium / titanium alloy is selected from one of TC4 titanium, TC6 titanium and TA1 titanium.

[0044] Optionally, the raw material of the tin layer is one of simple tin, Sn-xZn (0%<x≤30%) and Sn-ySb (0%<y≤50%), which is used to provide tin element and can generate Ti2Sn3 phase.

[0045] Optionally, the raw material of the zinc layer is one of zinc element, Zn-xAl (0%<x≤30%) and ZnAlCu system, which is used to provide zinc element and can generate TiZn3, TiZn 16 Mutually.

[0046] Optionally, the thickness of the tin layer is 10.50-12.50 μm, which is adjusted according to the surface requirements of the surface modification.

[0047] Optionally, the thickness of the zinc layer is 17.02 to 27.35 μm, which is adjusted according to the surface requirements of the surface modification.

[0048] Optional, vibration frequency: 20~30KHz; amplitude: 7~13μm.

[0049] The ultrasonic assisted brazing method of titanium-magnesium dissimilar metals comprises the following steps:

[0050] S1, fixing the surface-treated magnesium / magnesium alloy, the tin-zinc eutectic alloy intermediate layer and the titanium / titanium alloy together;

[0051] S2. Perform ultrasonic assisted brazing at a pressure of 0.05 to 0.2 MPa and a temperature of 200 to 300° C. to obtain a titanium-magnesium dissimilar metal joint.

[0052] Optionally, in S1, the surface treatment method of the magnesium alloy includes: grinding the surface to be welded flat with sandpaper, ultrasonically cleaning it with acetone and ethanol respectively, and then drying it with cold air to remove residual oil and impurities on the surface to be welded.

[0053] Optionally, in S1, the tin-zinc eutectic alloy intermediate layer is ultrasonically cleaned with acetone and ethanol respectively and then dried with cold air to remove residual oil and impurities on the surface to be welded.

[0054] Optionally, in S1, the magnesium / magnesium alloy is selected from one of AZ31 magnesium alloy, AZ31B magnesium alloy and AM60B magnesium alloy.

[0055] Optionally, in S1, the tin-zinc eutectic alloy intermediate layer is Sn-9Zn foil with a thickness of 20 to 100 μm.

[0056] Optionally, in S2, the temperature is raised to a set temperature and then kept at that temperature for 5 to 8 minutes, and then ultrasonic treatment is performed at the same temperature, and the furnace is cooled to below 100° C., with a vibration frequency of 30 to 40 KHz and an amplitude of 8 μm to 12 μm.

[0057] Optionally, in S2, the ultrasonic treatment time is 2 to 11 seconds

[0058] Optionally, in S2, the stacked raw materials are assembled into a mold, placed between the amplitude transformer and the heating furnace, welding pressure is applied through the amplitude transformer, and heating is performed through the heating furnace.

[0059] Example 1

[0060] A method for modifying the surface of titanium / titanium alloy, wherein metallic tin is used to modify TC4 titanium, and the steps include:

[0061] The surface of TC4 titanium was polished with sandpaper of 180-1200# to remove the oxide film on the surface of TC4 titanium sample; the polished TC4 titanium sample was placed in a mixed reagent (HF 15ml, HNO3 60ml, H2O 225ml) and soaked for 3 minutes to remove the residual oxide film on the surface of TC4 titanium; the TC4 titanium sample was then rinsed with water, polished with 2000# sandpaper, and finally ultrasonically cleaned with acetone and ethanol for 3-5 minutes to remove the oil on the surface, and then stored in ethanol.

[0062] A crucible containing tin (elemental tin) particles is placed in a muffle furnace, and the temperature is raised to a set temperature of 500°C and kept warm for 20 minutes to obtain molten metallic tin. After the insulation is completed, the treated TC4 titanium sample is placed in the crucible, and the titanium alloy is tin-plated by ultrasonic treatment at a vibration frequency of 20 KHz and an amplitude of 10 μm for 5 minutes, and then taken out and cooled naturally.

[0063] The obtained modified parts are as follows Figure 1 As shown: the modified tin layer can be combined with the TC4 titanium surface; the scanning electron microscopy results are as follows Figure 2 As shown: the thickness of the modified layer is about 8μm, and a Ti2Sn3 phase with a layer thickness of about 1 micron is generated; the TEM results are as follows Figure 3 Shown: High-resolution dark field image of the TiSn3 area; diffraction spot of the TiSn3 area after one FFT transformation.

[0064] Example 2

[0065] A method for modifying the surface of titanium / titanium alloy, wherein metallic zinc is used to modify TC4 titanium, and the difference from Example 1 is that tin (tin element) particles are replaced by zinc (zinc element) particles.

[0066] The obtained modified parts are as follows Figure 4 As shown: The modified parts obtained are as follows Figure 4 As shown: the modified zinc layer can be combined with the TC4 titanium surface to form a strong, uniform and defect-free zinc coating; the scanning electron microscope test results are as follows Figure 5 As shown: the thickness of the modified layer is about 27.35μm, and the TiZn3 phase with a layer thickness of about 10.05μm is generated; the TEM results are as follows Figure 6 As shown: TiZn3 and TiZn are generated on the surface of TC4 16 Mutually.

[0067] Example 3

[0068] A method for ultrasonically assisted brazing of titanium-magnesium dissimilar metals, wherein the modified TC4 titanium prepared in Example 1, a Sn-9Zn foil (tin-zinc eutectic alloy intermediate layer) with a thickness of 100 μm and an AZ31 magnesium alloy are selected as preparation raw materials, and the steps include:

[0069] S1. Use 600# sandpaper to polish the surfaces of the modified TC4 titanium and AZ31 magnesium alloys prepared in Example 1, respectively. Then, use acetone and ethanol to ultrasonically clean the polished parts and Sn-9Zn foil for 3 minutes, respectively, and then quickly dry them with cold air to remove the oil and impurities remaining on the surfaces to be welded. Align the cleaned magnesium alloy and titanium alloy surfaces to be welded and stack them, place the Sn-9Zn foil between the magnesium alloy and the titanium alloy, and assemble the stacked samples into a mold to form a weldment.

[0070] S2. A pressure of 0.15 MPa is applied to the upper surface of the weldment, and the welding temperature is set to 230°C. During the welding process, the temperature is raised to the set temperature of 230°C and kept at this temperature for 5 minutes. Ultrasonic treatment is then performed (vibration frequency: 30 IKHz; amplitude: 8 μm). The ultrasonic treatment time includes: 2s, 5s, 8s and 11s. Four specimens are obtained respectively. Finally, the weldment is cooled to below 100°C with the furnace, the pressure is released, and the mold is taken out to obtain a welded composite structure of titanium alloy and magnesium alloy.

[0071] The obtained welded composite structure is as follows Figure 7 As shown: There are no macroscopic defects on the bonding surface, and the results of the scanning electron microscope test are as follows Figure 8 As shown, Figure 8 (a) shows the microstructure of the tinned TC4 / AZ31 joint at 230°C and 2s ultrasonic treatment. Figure 8 (b) shows the microstructure of the tinned TC4 / AZ31 joint at 230℃ and 5 hours of ultrasonic treatment. Figure 8 (c) shows the microstructure of the tinned TC4 / AZ31 joint at 230°C and 8s ultrasonic treatment. Figure 8 (d) shows the microstructure of tinned TC4 / AZ31 joint at 230℃ and ultrasonic treatment for 11s.

[0072] The shear strength of the bonding surface of TC4 titanium and AZ31 magnesium alloy was tested. The results are as follows Fig. 9 As shown: when the welding temperature is 230℃, with the increase of ultrasonic time, the shear strength of the joint increases first and then decreases. At 5s of ultrasonic treatment, the maximum shear strength is 28.0MPa.

[0073] Example 4

[0074] A method for ultrasonically assisted brazing of titanium-magnesium dissimilar metals is disclosed, which differs from Example 3 in that the modified TC4 titanium prepared in Example 2 is used as a raw material, and other raw materials and preparation methods are the same as those in Example 3, and four test pieces are obtained respectively.

[0075] The obtained welded composite structure is as follows Fig.10 As shown: There are no macroscopic defects on the bonding surface, and the results of the scanning electron microscope test are as follows Fig.11 As shown, Fig.11(a) shows the microstructure of the galvanized TC4 / AZ31 joint at 230℃ and 2s ultrasonic treatment. Fig.11 (b) shows the microstructure of the galvanized TC4 / AZ31 joint at 230℃ and 5s ultrasonic treatment. Fig.11 (c) shows the microstructure of the galvanized TC4 / AZ31 joint at 230℃ and 8s ultrasonic treatment. Fig.11 (d) shows the microstructure of the galvanized TC4 / AZ31 joint at 230℃ and ultrasonic treatment for 11s.

[0076] The shear strength was tested and the results were as follows Fig.12 As shown: at 230°C, with the increase of ultrasonic time, the shear strength shows a trend of increasing and then decreasing), and the maximum shear strength is 48.0MPa when the ultrasonic time is 5s.

[0077] The present invention can be realized in the atmospheric environment without the need to operate in a vacuum environment. The transition layer is prepared by ultrasonically assisted pre-plating of titanium alloy, Sn-based brazing material is selected as the intermediate layer, the metallurgical reaction on both sides of titanium and magnesium is regulated, and the cavitation effect generated by ultrasonic waves in the liquid brazing material effectively removes the oxide film on the surface of titanium alloy and magnesium alloy, realizes welding in the atmospheric environment, and avoids the shortcomings of magnesium alloy oxidation and volatilization under high temperature conditions. Other processes require the welding of titanium / magnesium alloy in a vacuum environment or a non-vacuum environment + brazing agent, which increases working hours and costs.

[0078] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A titanium / titanium alloy surface modification method, comprising: After the titanium / titanium alloy surface is treated, ultrasonic-assisted hot-dip tin or zinc coating is applied; The ultrasonic-assisted hot-dip plating method is as follows: immersing the surface-treated titanium / titanium alloy into molten tin or zinc for 3 to 5 minutes, and applying ultrasonic waves to the molten tin or zinc during the insulation period.

2. The titanium / titanium alloy surface modification method according to claim 1, characterized in that: Titanium / titanium alloy is selected from one of TC4 titanium, TC6 titanium and TA1 titanium; Optionally, surface preparation methods include grinding, pickling, cleaning and drying.

3. The titanium / titanium alloy surface modification method according to claim 1, characterized in that: The raw material of the tin layer is one of simple tin, Sn-xZn and Sn-ySb, wherein 0%<x≤30%, 0%<y≤50%; optionally, the thickness of the tin-plated layer is 10.50-12.50 μm.

4. The titanium / titanium alloy surface modification method according to claim 1, characterized in that: The raw material of the zinc layer is one of zinc element, Zn-xAl and ZnAlCu system, wherein 0%<x≤30%; optionally, the thickness of the zinc-plated layer is 17.02-27.35 μm.

5. A method for ultrasonically assisted brazing of titanium-magnesium dissimilar metals, characterized in that: Includes steps: S1. Fixing together the magnesium / magnesium alloy after surface treatment, the tin-zinc eutectic alloy intermediate layer and the titanium / titanium alloy obtained by the titanium / titanium alloy surface modification method described in any one of claims 1 to 4; S2. Perform ultrasonic assisted brazing at a pressure of 0.05 to 0.2 MPa and a temperature of 200 to 500° C. to obtain a titanium-magnesium dissimilar metal joint.

6. The ultrasonic-assisted brazing method of titanium-magnesium dissimilar metals according to claim 5, characterized in that: In S1, the magnesium / magnesium alloy is selected from one of AZ31 magnesium alloy, AZ31B magnesium alloy and AM60B magnesium alloy.

7. The ultrasonic assisted brazing method of titanium-magnesium dissimilar metals according to claim 5, characterized in that: The tin-zinc eutectic alloy intermediate layer is Sn-9Zn foil with a thickness of 20 to 100 μm.

8. The ultrasonic-assisted brazing method of titanium-magnesium dissimilar metals according to claim 5, characterized in that: In S2, the temperature is raised to a set temperature and then maintained for 5 to 8 minutes, and then ultrasonic treatment is performed at the same temperature.

9. The ultrasonic assisted brazing method of titanium-magnesium dissimilar metals according to claim 5, characterized in that: In S2, the parameters of the ultrasonic wave are: vibration frequency: 30-40 KHz; amplitude: 8-12 μm.

10. The ultrasonic-assisted brazing method of titanium-magnesium dissimilar metals according to claim 5, characterized in that: The ultrasonic treatment time is 2 to 11 seconds.

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