Development and application of a ternary Ti-Al-N interatomic potential for Ti₂AlN/TiAl composite

Ti₂AlN/TiAl composite shows significant promise for using in high temperature structural material due to its excellent mechanical properties. However, an atomic scale understanding of the deformation and failure mechanisms under high temperature is still not well understand, this is mainly due to the lack of interatomic potential that accurately describe the interactions between Ti, Al and N atoms. To address this challenge, an interatomic potential of the Ti-Al-N ternary system has been developed on the basis of second-nearest-neighbor modified embedded atom method (2NN MEAM) formalism. Our newly developed 2NN MEAM potential accurately reproduces the structure, elastic, thermodynamics and surface properties of TiAl and Ti₂AlN compounds. Through molecular dynamics simulations using the developed potential, the atomic scale mechanisms underlying uniaxial tensile fracture of TiAl, Ti₂AlN and Ti₂AlN/TiAl composite are also reproduced in good agreement with experiments. These simulations indicate that both single crystal TiAl and Ti₂AlN undergoes brittle fracture at low temperature and shows ductile fracture at elevated temperature. When the tensile temperature is 300 K, the fracture behavior of Ti₂AlN/TiAl composite is only appeared in the TiAl side, the Ti₂AlN side and the interface region remain stable. But when the tensile temperature is 1200 K, the coherent interface becomes unstable and could act as the site for the dislocations nucleation. The interatomic potential for Ti-Al-N ternary system developed in this work could be utilized to further investigate atomic scale mechanisms underlying the response of Ti₂AlN/TiAl composite to the other external stimuli under high temperature, such as shear, compression and wear etc.