Microstructure characteristics and strain hardening behaviour of Ti17 linear friction welded joints

This study investigated the microstructure variations in Ti17 linear friction welded joints and evaluated the effect of strain rate and post weld heat treatment on the strain hardening behaviour. The welded zone of the as-welded joints consists of equiaxed β grains, while the prior-β grains in the thermal mechanical affected zone are severely deformed. After heat treatment, fine needle-like α_S precipitates dispersed in the β matrix strengthen the tensile properties. The fracture mechanism transforms from brittle to ductile. The strain hardening capacity and exponent are negatively correlated with strain rate. At higher strain rates, the strain rate sensitivity increases during the initial stage of deformation.