焊丝对T2紫铜/316L不锈钢GTAW接头组织及性能的影响

采用钨极氩弧焊，分别填充纯铜焊丝和307Si焊丝对T2紫铜/316L不锈钢异种金属进行对接焊，探究焊丝对铜/不锈钢异种金属接头微观组织、力学性能和耐蚀性的影响. 结果表明，铁-铜液相分离对焊缝组织的形成起主导作用，但由于过冷度不同，填充两种焊丝制备焊缝的液相分离程度不同:铜焊丝制备焊缝中生成了初次液相分离富铁球，其内部又发生二次液相分离现象，生成富铜相；307Si焊丝制备焊缝中生成了初次液相分离富铜相，但富铜相并未呈现二次液相分离特征. 两种焊丝制备接头在拉伸试验中均断裂于铜侧热影响区，抗拉强度均超过铜母材强度的80%. 拉伸断口分布着韧窝和延伸区，呈现典型的韧性断裂特征. 腐蚀及电化学试验结果表明，与307Si焊丝制备接头相比，铜焊丝制备接头的腐蚀深度差更大，腐蚀电流密度更高，耐蚀性更差.

Effect of filler metals on microstructure and properties of T2 copper/316L stainless steel GTAW joint

T2 copper/316L stainless steel dissimilar joints were produced by gas tungsten arc welding with Cu filler wire and 307Si filler wire, respectively. The effect of filler metals on microstructure, mechanical properties and corrosion resistance of the joints was investigated. The microstructure of copper/steel weld was largely affected by liquid phase separation between iron and copper. When Cu filler wire was used, Fe-rich spherulites formed by Fe-Cu primary liquid phase separation distributed in the weld. Inside the Fe-rich spherulites, minority Cu-rich spheres formed by secondary liquid phase separation. However, when 307Si filler wire was used, the primary liquid phase separated Cu-rich spherulites showed no characteristic of secondary liquid phase separation. The tensile specimens achieved by both filler wires fractured at HAZ on the copper side, and the strength of each joints reached at least 80% of Cu base metal. Dimples and stretched zone were distributed on the fracture, showing the ductile fracture mode. Compared to the joint achieved by 307Si filler wire, the joint achieved by Cu filler had larger corrosion depth and corrosion current density, showing an inferior corrosion resistance.