Quantifying the role of interface atomic structure in the compressive response of Ti₂AlN/TiAl composite using MD simulations

Unraveling the effects of interface atomic structures on the mechanical properties is a key step toward the elaborate design of Ti₂AlN/TiAl composite with excellent performance. However, the impact of different interface atomic structures upon the mechanical properties of Ti₂AlN/TiAl composite, which is extremely important from the perspective of material design, remains poorly understood and essentially unquantified so far. In this research work, molecular dynamics simulations of Ti₂AlN(0001)/TiAl(111) coherent interface and \( {\text{Ti}}_{2} {\text{AlN}}(10{\bar{\text{1}}}3)/{\text{TiAl}}\left( {111} \right) \) incoherent interface system under parallel-to-interface compression are carried out. It is found that these two types of interface systems show different compressive deformation behaviors due to significantly different interface–dislocation interactive mechanisms. The compressive ultimate strengths of Ti₂AlN(0001)/TiAl(111) coherent interface and \( {\text{Ti}}_{2} {\text{AlN}}(10{\bar{\text{1}}}3)/{\text{TiAl}}\left( {111} \right) \) incoherent interface systems are comparable, but the ductility of incoherent interface system is obviously higher than that of coherent interface system. This is because the incoherent interface can simultaneously serve as the source for dislocation nucleation and the barrier for dislocation motion, and thus plays a dual role of softening and hardening in the compressive deformation. Therefore, it can be expected that tuning the interface with \( {\text{Ti}}_{2} {\text{AlN}}(10{\bar{\text{1}}}3)/{\text{TiAl}}\left( {111} \right) \) incoherent atomic structure can contribute to increasing the compressive ductility of Ti₂AlN/TiAl composite without lowering its strength.