Tailoring microstructures induces recrystallization to eliminate cracks of TiAl alloy fabricated by linear friction welding

: Linear friction welding (LFW) is considered a suitable method for preparing the blisk of TiAl alloys. However, due to the intrinsic brittleness of TiAl alloys, the linear friction welded joints are susceptible to cracking. In this study, the influence of base materials characterized by fully lamellar (FL), near-lamellar (NL) and duplex (DP) microstructures on weldability and mechanical properties of joints were investigated. The crack-free LFW joint was obtained for the TiAl alloy with DP microstructure, and the ultimate tensile strength of joint was equal to that of base material (BM). The joint was divided into welding zone (WZ), thermal mechanical affected zone (TMAZ), and BM. Compared with FL-TiAl and NL-TiAl alloys, the high Ti/Al atomic ratio and addition of strong β-stabilizing element Mo promote the formation of B2 phase at the grain boundary of DP-TiAl alloy. And the fine α 2 /γ lamellar colony and B2 phase provide the deformation capability for the LFW DP-TiAl alloy joint. The stored strain energy and residual stress in the joint are released by dislocation migration during the complete dynamic recrystallization (DRX). The existence of B2 phase provide the improvement of ductility and elimination of cracks of LFW joint.