Hybrid welding of AA5754 annealed alloy: Role of post weld heat treatment on microstructure and mechanical properties

In this paper hybrid welding of the annealed AA5754 alloy was studied and the role of post weld heat treatment (PWHT) on microstructure and mechanical properties was investigated. The microstructure and hardness of the base material andwelds were analyzed. Due to the segregation, the lowest microhardness value was observed at the welding centerline. High microhardness was registered in a narrow zone at the interface between the fusion zone and the heat affected zone where the welding cycle promotes both the strengthening byMg solid solution and the lowest grain size. The hardness of the heat affected zonewas higher than that of the base material due to dissolution of soluble particles (Mg2Si and Mg2Al3). PWHT at 350 °C increased the microhardness in the fusion zone and the tensile strengthwith respect to the untreated joint,whereas the strain at fracturewas similar showing that the fracturewas promoted mainly by the presence of porosity, coarse grain size and insoluble segregated second phases.