1991 Volume 9 Issue 1 Pages 136-142
Susceptibility to weld solidification cracking of three kinds of Ti-alloys was investigated by Trans-Varestraint test. Weld crackings did not occur in Ti-6Al-4V at all, but significantly occurred in Ti-6Al-6V-2Sn and Ti-15V-3Al-3Cr-3Sn. Ti-15V-3Al-3Cr-3Sn was actually the most susceptible to cracking. Through close examination of weld solidification microstructures by tin-quenching, conspicuous segregations of V, Cr, Cu and Fe were confirmed at dendritic grain boundaries during solidification in each alloy The diffusion rate of solute elements in Ti-6A1-6V-2Sn and Ti- I5V-3A1-3Cr-3Sn was I order smaller than that in Ti-6Al-4V. Consequently, the amount of compositional microsegregation at dendritic boundaries in the former alloys was larger, because the effect of solid diffusion during solidification was smaller. In Ti-6Al-4V, these microsegregations were readily decreased and eliminated by the occurrence of solute diffusion at very early stage of weld cooling, while that in the other alloys remained till rather lower temperature to cause crackings due to liquid films of low-melting constituents.
