The Effect of Preheating on Notch Fracture of Ti-4.5Al-3V-2Fe-2Mo Laser Welds

Abstract

Notched tensile strength (NTS) and impact fracture toughness were determined for Ti-4.5Al-3V-2Fe-2Mo laser welds subjected to post-weld heat treatment (PWHT) at distinct temperatures. In the welding process, the specimens were preheated at 300°C to reduce the cooling rate of the welds, and the results were compared with the non-preheated welds. Generally, the preheated welds had coarser α+β structures and showed slower responses to age-hardening in PWHTs than the non-preheated welds. The decreased hardness and accompanied ductility enhancement resulted in the improved notch brittleness and impact toughness of the preheated welds, relative to the non-preheated welds. As the PWHT temperature of the welds increased, the coarsening of grain boundary α assisted grain boundary sliding and formed intergranular dimple fractures on the fracture surface.