Influence of heat input on the intermetallic compound characteristics and fracture mechanisms of titanium-stainless steel MIG-TIG double-sided arc welding joints

Abstract

The influence of the heat input on the intermetallic compound (IMC) characteristics and the fracture mechanisms of titanium-stainless steel MIG-TIG double-sided arc welding (DSAW) joints using Cu–Si welding wire were studied. The results show that the MIG-TIG DSAW method can effectively control the microstructural characteristics by the heat input regulation. The Ti side interfaces were composed of IMC layers, mainly of Ti–Cu phases, and the thickness of the layers increased with increasing heat input. At the low heat input, the joints fractured at the 304SS side interface, which was embrittled by the straight IMC layer with the brittle TiFeSi and λ, Ti(Fe1-xSix)2 (0-x-0.375) phases. With increasing heat input, the melting of the 304SS reduced the interface brittleness by dispersing the brittle λ phase by softer Fe (s,s) and Cu (s,s) phases. At the high heat input, with the melted zone separated from the base metal, the remain-curved 304SS side interface improved the tensile resistance by increasing the load-bearing area. The fracture occurred at the Ti side interface, which embrittled by the thick IMC layers with a thickness greater than 130 μm. With the increase of the heat input, the joints showed an increase in tensile strength at the 304SS side interface but a decrease at the Ti side interface. The optimal tensile strength of 320 MPa was thus obtained in the joint under intermediate heat input, with a fracture position mixed with the Ti side interface and 304SS side interface.