Crack formation and control upon the electron beam welding of TiAl-based alloys

Electron beam welding experiments on 2.5-mm-thick as-forged Ti-43Al-9V-0.3Y intermetallic plates were carried out. Cold cracking occurred in the direct electron beam welding joints because of the brittleness of the microstructure and the residual stress. A crack-free electron beam welding joint was obtained by a new composite control method. This process can prolong the high temperature stage to promote the phase transformation and to give the expected microstructure of the joint. The microstructures and tensile strengths of the joints were examined by TEM, X-ray diffraction, electron back scattering diffraction and universal test machine. The weld obtained by the composite control method was characterized by an analysis of the combined phase structure of the γ_m grain and the γ/α₂ colony microstructure. The tensile strength of the joint that was obtained by the composite control method was found to be 411.3 MPa, which is 20% higher than the direct welding joint.