Development of crack-free welds in a TiAl-based alloy

Weldability of a Ti–45Al–2Nb–2Mn+0.8TiB2 alloy using electron beam welding process was investigated. It was found that the susceptibility of the alloy to solid-state cracking was due to the suppression of decomposition of the α phase and thermally induced stresses. The crack-free weld could be made on small-size workpieces when the weld cooling rate was properly controlled to allow the α phase to fully decompose. But when welding was conducted on highly restrained workpieces, the role of phase transformation was overshadowed by the stresses induced by the constraint in welds and the alloy became extremely difficult to weld.