A Novel Approach of Microstructure Refinement of TiAl in Laser Beam Welding

Grain refinement through borides is known to be suppressed when TiAl welded with a laser beam. As β grains do not primarily nucleate on boride at high cooling rate, mixture of nitrogen and argon applied as protecting gas for the formation TiN during solidification. The phase transformation changed correspondingly from Liquid → + α γ+ α2 γ B2 β+ TiN. It found that prefer heterogeneously suspending in melt orientation relationship {111}TiN//{110}β, leading refined grains. colonies were thus modified into fine non-dendritic effects shielding atmosphere microstructure evolution are elaborately studied.