ELECTRON-BEAM WELDING OF A TI-45AL-2NB-2MN-PERCENT TIB2 XD ALLOY(0.8 VOL)

The feasibility of using conventional electron beam welding to join a Ti-45A1-2Nb-2Mn + 0.8% TiB2 XD alloy was assessed. The alloy showed no evidence of hot cracking. However, a susceptibility to solid-state cr acking was observed when weldments cooled at high cooling rates. The m icrostructural features of weldments were found to be a function of we lding speed, heat input, preheating temperature, and thus cooling rate . Effects of cooling rates on microstructural evolution was evaluated with thermal simulation in a Gleeble 1500 system and it was found that cracking occurred when high cooling rates resulted in suppression of the alpha+gamma phase transformation. It was observed that sound welds could be made when welding conditions were chosen so that the cooling rate at the fusion zone boundary was 250 Ks(-1) or less. (C) 1997 Els evier Science S.A.