The effect of rolling direction on the weld structure and hardness of gamma-TiAl sheet material

The microstructure and microhardness of a welded gamma-TiAl (γ-TiAl) sheet material was investigated to determine the effect that rolling direction had on its microhardness and microstructure. The alloy was received in the primary annealed condition which consisted of a microstructure containing equiaxed γ grains with α2 particles located at grain boundaries and triple points. Gas tungsten arc welding was performed both along and transverse to the direction of rolling. The fusion zone consisted of a dendritic microstructure with some microporosity. The microhardness of the fusion zone was significantly harder than the base metal regardless of rolling direction. Preliminary results showed that the specimens welded transverse to the rolling direction had cracks that were parallel to the welding direction (normal to the rolling direction) and the cracking was much more severe than for the specimens welded in the direction of rolling. A preliminary weld structure-property relationship was established as a function of rolling direction.