Observations on welding of alpha(2)+O+beta titanium aluminide

The weldability characteristics of an x(2) + O + beta titanium aluminide of nominal composition Ti-24Al-15.5Nb (at-%) have been investigated. Conventi onal gas tungsten are (GTA) and electron beam (EB) welds, exhibited columna r fusion zone grains. Pulsed current and arc oscillated GTA welds exhibited predominantly equiaxed fusion zone grains. The microstructure of GTA welds and pulsed current GTA welds exhibited x(2) + O phases, whereas are oscill ated GTA welds and EB welds contained x(2) + O + beta (0)/beta (2): however , beta (0)/beta (2) is predominant in EB welds. The EB welds, which contain ed alpha (2) + beta (0)/beta (2) microstructure, exhibited high strength an d ductility compared with GTA welds. The observed microstructural variation s are explained on the basis of possible weld thermal cycles and convective currents in the weld pool.