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Direct Friction Welding of TiAl Alloy to 42CrMo Steel Rods

The effect of post-weld heat treatment (PWHT) on the mechanical properties and microstructure of direct friction-welded joint between TiAl alloy and 42CrMo steel rods was investigated in this paper. It was found that solid joint between TiAl alloy and 42CrMo steel could be obtained without adding interlayer. After PWHT at 580°C for 2 h, the tensile strength of the joint reached 405 MPa, and fracture happened through the TiAl alloy substrate with quasi-cleavage features. The tempered sorbite formed near the interface, improving the joint strength significantly. It was found that TiFe2, TiAl, and small amount of TiC brittle phases formed at the interface, and the interfacial layer was as thin as 2–5 µm. The precipitated phases were 1 µm in average size, and distributed discontinuously at the interface.