The role of γ/γ interfacial spacing on the tensile behavior in lamellar TiAl alloy via molecular dynamics simulations

The lamellar microstructure is one of the most typical microstructures of TiAl alloys. There are three γ/γ interfaces with different microstructures in lamellar γ-TiAl alloys. In this work, we investigated the deformation processes of lamellar γ-TiAl alloys with different interfacial spacing (λ) via uniaxial tensile loading using molecular dynamics simulations, including true twin (TT), pseudo-twin (PT), rotational boundary (RB), and the mixed structure (TT ∥ PT ∥ RB). The results show that in all lamellar γ-TiAl samples, the Shockley partial dislocation prefers to nucleate in the region between two neighboring interfaces. Then, dislocations move towards, crossing the γ/γ interface. Finally, the dislocation slippage leads to the destruction of the interface, resulting in cracks and structural failure. With the decrease of λ, the ultimate strength slightly increases in the TT or PT structure of γ-TiAl, which follows the Hall-Petch relation. But in general, the interfacial spacing has a slight effect on the ultimate strengths of these four structures of γ-TiAl.