Investigating the effects of phosphorus in a binary-phase TiAl-Ti

We investigate the site preference of phosphorus (P) and its effects on the mechanical properties of the binary phase TiAl-Ti3Al alloy using a first-principles method in combination with empirical criterions. We show that P is energetically sitting at the substitutional Al site in the Ti3Al layer of the TiAl/Ti3Al interface, which can be understood from the difference of electronegativity between P and Ti/Al. Both the cleavage energy (γcl) and the unstable stacking fault energy (γus) decrease with the presence of P, which indicates the strength of the TiAl/Ti3Al interface will be weaker and the mobility of the dislocation will be easier induced by P. Further, we demonstrate that the ratio of γcl/γus of TiAl/Ti3Al interface with P is 5.03, 0.19% lower than that of the clean TiAl/Ti3Al interface, suggesting that the P impurity will slightly reduce the ductility of the TiAl/Ti3Al interface