Assessment of fracture and fatigue crack propagation of laser beam and friction stir welded aluminium and magnesium alloys

The fracture strength and fatigue crack propagation behavior, of laser beam and friction stir welded aluminum and magnesium alloys, was investigated. The investigations were performed on LBW and FSW welds of 6XXX Al-alloys and wrought AZ32B Mg-alloy. The properties were studied in terms of microstructure- property-performance relationships, and it was found that high strength Al-alloys and the Mg-alloy AZ31B could be successfully laser beam welded. High strength 6XXX Al-alloys series exhibited strength leading to strain localization in the weld, and loss of strength. The strain localization behavior and the fatigue crack propagation behavior could not be improvized by a post weld heat treatment. It was found that increasing the local thickness of the base metal (pocketing), the crack could be made to deviate from the weld into the base metal under static tensile loading. The socket geometry was found critical for crack deviation in cyclic loading.