The Effect of Preheating on Notched Tensile Strength and Impact Toughness of Ti-6Al-6V-2Sn Laser Welds

Abstract

Notched tensile strength (NTS) and impact toughness were determined for Ti-6Al-6V-2Sn laser welds subjected to post-weld heat treatment (PWHT) at distinct temperatures. In this study, the specimens were either preheated at 300 C or maintained at room temperature before laser welding. The preheated weld, associated with a reduced cooling rate, had obviously lower hardness than the non-preheated weld in the as-welded condition. After PWHT at 482 C for 3 h, the preheated weld also exhibited considerably lower hardness than the non-preheated weld. In general, preheating at 300 C could effectively increase the NTS and impact toughness of Ti-6Al-6V-2Sn laser welds. The preheated weld in the as-welded condition had superior NTS to other welds being tested. On the other hand, the welds after PWHT at 704 C possessed the best resistance to unstable impact fracture, regardless of preheating. Usually, the coarse þ structures together with intergranular were responsible for the high NTS and impact toughness of the weld. [doi:10.2320/matertrans.M2010281]