Tailoring α ₂/γ And γ/γ Interfaces in TiAl Alloys Via Segregation: A Multiscale QM/MM Study

Abstract

In this study we present an implementation of a coupled multi-scale quantum mechanics/molecular mechanics approach well suited for studying compositionally-rich extended defects. Our focus is on interfacial phenomena of γ/γ and α₂/γ grain boundaries in intermetallic TiAl alloys. We prove that our implementation is capable of accurately reproducing site-preference energies of solutes reported by previous Density Functional Theory studies. To properly study segregation phenomena, we developed a formalism for segregation energies in systems with two sublattices (Ti and Al). Our model provides predictions consistent with atom probe tomography measurements reported in literature for a large number of solute atoms. Finally, we quantify the impact of solute segregation on the mechanical properties of the interfaces.

Keywords: Multiscale simulations, Ab-initio calculations, Titanium aluminides, Interface segregation, Mechanical properties, QM/MM