Molecular dynamics simulations of lattice site preference and phase separation in B2-NiAl with Pt addition

Pt-modified beta-NiAl is an alloy of special interest for bond coatings in the hot sections of the engines. Nevertheless, the site occupancy of Pt is still an open issue. In this work, we have constructed a Ni-Al-Pt interatomic potential and carried out the molecular dynamics simulations to reveal the atomic structures and displacement behaviours of Pt in B2-NiAl. The results of the simulations not only show that the Pt atoms have a strong preference for the Ni site in B2-NiAl but also suggest that an increasing Pt concentration leads to a more pronounced displacement of the Al atoms. Moreover, the simulations predict the occurrence of phase separation in B2-NiAl when the Pt concentration reaches 20%, which is confirmed in the subsequent experiments by the formation of a beta-NiAl+Al2Pt dual-phase structure. The present findings promote the understanding of the atomic structures in B2-NiAl, which in turn may provide useful guidance for the fabrication of high-quality beta-NiAl bond coatings. (C) 2017 Elsevier B.V. All rights reserved.