Tensile properties and fracture behaviors of electron-beam welded Ti6242 titanium alloy joints

Abstract

The microstructure, tensile properties and fracture behaviors of electron-beam welded Ti6242 titanium alloy joints were systematically investigated. The as-received alloy exhibited a typical duplex microstructure consisting of equiaxed primary α phase and laminated secondary α phase/β phase. The high cooling rate during welding resulted in substantially microstructure evolution in the fusion zone (FZ) of the joints, leading to the formation of large columnar β grains with embedded acicular α′ martensitic phase platelets. The influences of such microstructure variations on the mechanical properties and fracture behaviors at different temperatures were analyzed and discussed. In principle, the hard-yet-brittle α′ martensitic phase induced significantly strengthening of the FZ. As a result, for the un-notched specimens, the plastic deformation was concentrated to the soft base material with subsequent ductile fracture via micro-void coalescence mechanism. But for the notched specimen, in which the notch located just within the FR, cracks initiated and proceeded along the FR in a brittle manner.