Ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys

In the casting of single-crystal turbine blades, the composition (c) and temperature (T) dependencies of the liquid-phase molar volume (V (c, T)) play a critical role in driving convective instabilities and the associated formation of solidification defects. In support of an effort aimed at the development of validated mathematical criteria for predicting the formation of solidification defects in Ni-based superalloys, ab-initio molecular dynamics (AIMD) simulations have been performed to calculate atomic volumes of Ni-Al-W melts. For elemental Ni and binary Ni-Al and Ni-W compositions, AIMD-calculated volumes agree to within 0.5-1.5% of recently measured values. For ternary Ni-Al-W melts, where direct experimental measurements are unavailable, AIMD results are in excellent agreement with the predictions of a proposed parametrization for V (c, T) in multicomponent superalloys. The results thus help to establish the accuracy of this proposed model in its application to the Ni-Al-W system