Study on microstructure and mechanical behavior of dissimilar Ti17 friction welds

Dissimilar welds of Ti17 alloy with lamellar and bimodal structures were produced by friction welding. Microstructural characterizations were performed by means of optical, scanning and transmission electron microscope as well as X-ray diffraction analysis. Mechanical evaluations were conducted by determining microhardness and fracture toughness both in as welded and post weld heat treated (PWHTed) conditions. The results show that in as welded condition, the minimum microhardness and fracture toughness were observed in the weld center. However, in PWHTed condition, the microhardness of weld center was enhanced to a maximum while the toughness was decreased. This is thought to be resulted from fine α and β precipitations upon post weld heat treatment.