Phase stability and mechanical properties of ternary transition elements X(X = Cu,Zn,Ag) in Al3Hf intermetallic from first-principles calculations

Abstract

Site preference, phase stability and brittle vs ductile behaviors of ternary transition elements Cu, Zn and Ag in Al3Hf intermetallic are investigated by using of first-principles calculations. It is found that it has a phase transition from D023 phase to L12 phase for Al3Hf due to the strong Al site preference for Cu, Zn and Ag addition. It is shown that the role of activated antiphase boundaries on 〈110〉(001) plane is the key factor for the phase transition. Elasticity modulus show that ternary elements can effectively improve the ductility of Al3Hf due to the phase transition. Finally, cleavage fracture model and slip fracture model were used to give a prediction of brittle to ductile transition mechanism based on Griffith fracture theory. The energetic results show that the improved ductility is due to the activated dislocation emission but suppressed crack propagation in materials.