Microstructure and mechanical properties of ultrasonic spot welded Al/Ti alloy joints

摘要

The microstructure, hardness, and tensile properties of solid-state ultrasonic spot welded (USWed) dissimilar joints between Al5754-O and Ti-6Al-4V alloys with or without a pure Al interlayer were studied. Significant difference in the microstructure was observed at the interface of the USWed Al/Ti alloy joints, where the phenomenon of adhesion on each side of the joint with Al interlayer was more obvious than that of the joint without Al interlayer. An asymmetrical hardness profile across the dissimilar joint was observed such that the hardness value increased gradually from the Al side to the Ti side. With increasing energy input, the lap shear strength of the USWed Al/Ti alloy joint with a 75 μm thick Al interlayer first increased and then decreased, with the maximum lap shear strength reaching about 206 MPa at a welding energy of 1000 J. No samples failed at the interface when the energy was above 1000 J or the thickness of Al interlayer was more than 75 μm. The fracture was predominantly characterized by the dimple-like ductile fracture.