Formation and fatigue property of MIG welded high-speed train 6005A-T6 aluminum alloy

Abstract

In this paper the MIG welding is used for high-speed train 6005-T6 aluminum alloy welding experiments. The microstructure, micro-hardness, tensile property and fatigue property of base metal and welded joint have been analyzed with optical microscopy (OM), micro-hardness machine, scanning electronic microscopy (SEM), tensile test machine and fatigue test machine, respectively. It was found that isometric crystals exist in the welds. The crystals in heat affected zone are bigger than base metal s. The width of the heat affected zone is 25 mm. There is softening zone in the heat affected because of the redissolution and separating out of strengthening phase, and the minimum micro-hardness is 50 HV. The tensile strength of welded joint is 191 MPa up to 67% of the base metal, and the fracture is ductile fracture. Sheet and rod strengthening phases, fatigue strips and secondary cracks exist in base metal fatigue fracture that has cleavage fracture and ductile fracture characteristics. River pattern, secondary cracks, and brittle fatigue stripes exist in welded joint fatigue fracture that is cleavage fracture.