Strengthening the Ti/TiN Interface Against Shear Failure with Al Dopants: A Molecular Dynamics Study

The impact of Al doping on the stability and shear strength of the Ti/TiN interface was investigated using a newly developed modified embedded atom model interatomic potential. The model was parameterized to the inter-facial properties of pure Al, TiAl and AlN binaries as well as TiAlN ternary system. The results of the new model are in reasonably good agreement with those obtained using Density Functional Theory and experimental data from the literature. A Ti/TiN system with a misfit dislocation network present on the Ti layer adjacent to the TiN interface was chosen for doping because of its low interfacial energy. To find the most likely configuration of Al atoms in Ti/TiN, a Monte Carlo scheme was developed. A range of Al compositions were studied, in which higher Al composition caused a more negative enthalpy of mixing up to 25 mol%. Even at small Al compositions, a drastic increase in shear strength was observed, continuously increasing with increasing Al composition. The highest Al composition had an abundance of screw dislocations, which were found to be responsible for its high shear strength.