The direct friction weldability of TiAl alloy and 42CrMo is poor, so the friction welding process of TiAl and GH3039/K418/N80A/N6 dissimilar materials was studied by introducing superalloy GH3039, K418, N80A and N6 as intermediate materials. The hardness, microstructure, composition and mechanical properties of welded joint were analyzed by hardometer, scanning electron microscope and universal tester. Studies had shown that complex intermetallic compound layers were formed at the weld interface of TiAl alloy and dissimilar materials; Additionally, the friction weldabilities of TiAl with GH3039 and N80A are better than that with K418 and N6; GH3039 is selected as the intermediate material to improve the friction weldability of TiAl alloy and 42CrMo dissimilar material based on a) the linear expansion coefficient that varies with temperature, b) the tensile strength of the welded joints with TiAl, and c) the friction weldability with structural steel 42CrMo. By introducing the intermediate material, the integral rotors of TiAl turbine + 42CrMo shaft are obtained, which represents a practical application of TiAl alloy in the field of the turbocharger.