Pt effects in γ-Ni(Al)/α-Al2O3 adhesion

We present a systematic first-principles density-functional theory (DFT) study of the effects of Pt on the adhesion of the γ-Ni(Al)/α-Al2O3 interface, in a close comparison with those of Hf and S. Both the thermodynamically preferred Al-rich and the stoichiometric interfaces are considered. S is found to segregate to and substantially weaken both interfaces. Hf can pin S in bulk γ-Ni even at temperatures as high as 1,600 K, effectively inhibiting S segregation, while Pt cannot, due to phonon effects. For the stronger, Al-rich interface, both Hf and Pt have larger heats of segregation than S, inhibiting S segregation through preferential segregation. For the weaker, stoichiometric interface, Hf can significantly strengthen its adhesion to be as large as that of the Al-rich interface, and also inhibit S segregation through preferential segregation. Pt, as a contrast, can neither inhibit S segregation nor directly enhance the interface bonding.