Hot deformation behavior of a layered heterogeneous microstructure TiAl alloy prepared by selective electron beam melting.

TiAl-based alloys are known for their exceptional high-temperature properties but suffer from low hot workability. The emergence of additive manufacturing (AM) technology significantly decreases the workability requirement, while the microstructure heterogeneities in AMed TiAl are troublesome. This paper explores the hot deformation behavior and microstructure evolution of a layered heterogeneous microstructure TiAl alloy prepared by selective electron beam melting. The Arrhenius constitutive model with strain compensation was established, and hot processing maps were constructed. The microstructure showed that at the initial stage of deformation, a large number of dislocation slips occur preferentially in the soft coarse-grained layers. With the increase of strain, dislocation accumulation in heterogeneous interfaces, and dynamic recrystallization (DRX) occurs. Eventually, the coarse-grained region is constantly occupied by fine DRX grains. A high density of deformation twins at high strain rates further promotes the formation of tiny DRX grains. When the hot compression temperature reaches 1200 °C, the initial alternative fine-grained and coarse-grained hetero-structure transforms into duplex (DP) and near-lamellar (NL) microstructure, and microstructure heterogeneity is eliminated. The results enhance understanding of the hot deformation behavior of heterogeneous microstructure TiAl alloys. • Constitutive equation and processing map of heterogeneous TiAl alloy are established. • Thermal plastic deformation promoted the elimination of microstructure heterogeneity. • Coarse-grained and fine-grained layer exhibit different deformation mechanisms. [ABSTRACT FROM AUTHOR]