A cluster-induced structural disorder and melting transition in the grain boundary of B2 NiAl: a molecular-dynamics simulation on parallel computers

A structural disorder and melting transition of the S = 5 bicrystalline interface of B2 NiAl with a large boundary plane is investigated by molecular-dynamics simulations. The calculations have been performed at various temperatures using an embedded-atom-method potential fitted to NiAl. It is observed that the atoms in the grain-boundary region tend to form clusters in a thermal structural disorder transition, which is initiated at a temperature well below the thermodynamic melting point T m (around 0.52 T m ). The number and size of the clusters are monitored over a wide temperature range including T m . Below T m , the number and size of the clusters increase continuously with increasing temperature. At temperatures up to T m , the abrupt increase in size of the clusters induces melting. At temperatures above T m , the number and size of the clusters decrease significantly upon raising temperature. The calculations of the potential energy also indicate that the thermal disorder transition is a continuous process, in contrast to the first-order melting transformation.