Microstructure Evolution and Mechanical Properties of Linear Friction Welded TiAl Alloy Joint with Online Stress Relieving

Crack-free TiAl joints were welded by linear friction welding with online stress relieving process. Microstructural examination demonstrates that the joint has a clearly identified weld zone which consists mainly of equiaxed γ grains with a few α₂ phase. Lamellar grains in thermo-mechanically affected zones near the weld margin are oriented along with the flow direction of the plasticized material. The microhardness of the joint presents a global increase from the base metal to the weld interface by about 1700 MPa; the tensile strength of the joints ranges from 683 MPa to 717 MPa at ambient temperature, which is comparable to that of the base metal. The refinement strengthening contributes to enhancing the joint strength.