Investigations of microstructures and properties in electron beam welded joints of TiAl to TC4

The normally centered electron beam and non-centered electron beam welding of TiAl to TCA was investigated in order to analyze the electron beam weldability between TiAl/TC4 dissimilar materials. Macroscopic cold crack easily occurred near TiAl substrate in the joints. The optimal tensile strength was related to the welding heat input. The weld structures were composed of bulky columnar grains and equiaxed grains. The isolated phases consisted of large quantities of α₂-Ti₃Al phase, small quantity of B2 phase, γ-TiAl phase and YAl₂ phase. Insufficient melting of the base metal occurred in the weld when the beam position leaned to the TCA side. The tensile strength could be improved when the deflection was limited in the optimum range. Otherwise, non-fusion zone was easily generated in the weld, which led to the low tensile strength.