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异种金属的有效连接在高新技术领域具有实际意义,采用电阻点焊方法焊接稀有金属钨片和镍丝。用SEM,HRTEM表征焊接接头的组织形貌,用拉伸试验机测定焊接件的抗剪切力。采用如下焊接工艺:第一阶段:预压力是100 N,使钨镍良好接触;第二阶段:保持预压力不变,施以预热电流1.1 kA、400 ms,然后再施以焊接电流1.7 kA、400 ms;第三阶段:保持100 N的电极压力60 ms;最后,撤去电极压力。HRTEM结果表明:钨镍之间通过高温原子扩散形成置换固溶体而形成有效的连接,且在钨镍界面上没有新相形成。SEM结果表明焊接接头的镍丝没有翘头,且边缘没有严重压扁现象。经上述工艺得到的焊接接头的抗剪切力约为40 N,符合焊接件技术要求。
The effective connection of dissimilar metals is of practical significance in the field of high-tech fields, using the method of resistance spot welding to weld rare-metal tungsten sheets and nickel wires. The microstructure of the welded joint was characterized by SEM and HRTEM, and the shear resistance of the welded part was measured by tensile testing machine. The following welding process is adopted: Stage 1: The pre-pressure is 100 N, making good contact with tungsten-nickel; Stage 2: Preheating current 1.1 kA, 400 ms, and then welding current 1.7 kA , 400 ms; Stage 3: hold the electrode pressure of 100 N for 60 ms; and finally, remove the electrode pressure. HRTEM results show that tungsten and nickel can form effective connection between high-temperature atom diffusion and substitutional solid solution, and no new phase is formed on tungsten-nickel interface. The SEM results show that the nickel wire of the welded joint is not warped and the edge is not severely squashed. The shear resistance of the welded joints obtained by the above process is about 40 N, which meets the technical requirements of the welded parts.