Interfacial microstructure evolution and mechanical properties of TC4 alloy/304 stainless steel joints with different joining modes

Abstract

TC4 alloy(Ti)/304 stainless steel (SS) plates were butt joined using MIG-TIG double-sided arc welding(DSAW) with copper filler metal. Different joining modes, i.e., brazing mode, welding-brazing mode (Ti welding-SS brazing, SS welding-Ti brazing) and fusion welding mode, were achieved by regulating the welding parameters. The interfacial microstructures and mechanical properties of the joints were investigated. The results show that the interfacial microstructures and mechanical properties are strongly affected by the joining mode.For the joints with brazing mode and Ti welding-SS brazing mode, a straight Intermetallic compound(IMC) layer of Fe-Cu-Si and Ti-Fe-Cu-Si phases was respectively formed at the SS side brazing interface, resulting in the fracture at lower stress; the Ti side brazing and fusion interfaces both mainly consisted of Ti-Cu IMC layer. The joints with SS welding-Ti brazing mode and fusion welding mode led to the curved melted zone containing two phases of Fe(s,s) and Cu(s,s) at the SS side fusion interface. The tensile resistance of the interface was significantly enhanced attributed to the curved morphology and the suppression of the brittle IMCs. The fractures occurred at the Ti side interface, and the tensile strength was determined by the thickness of the reaction layer consisted of the Ti-Cu and Ti-Cu-Fe IMCs. Therefore, the SS welding-Ti brazing joint with a thinner reaction layer shows the maximum tensile strength, which is up to 319 MPa.