Order-Disorder Transformations in the σ3 (111)/[110] Symmetrical Tilt Boundary in Tungsten

Abstract

ABSTRACTThe structure of the σ3 (111)/[110] symmetrical tilt boundary in tungsten was modeled by molecular statics using Finnis-Sinclair type many body potentials. Several multiple structures have been found which are composed of two types of structural units and the interaction energy between these units is negative. Hence, order-disorder structural transitions may occur in the boundary with structures being ordered and/or disordered mixtures of the two units. The uansilion temperature is found to be 1158K if only the internal energy and configurational entropy arc included when evaluating the free energy. However, the transition temperature is 782K if the vibrational entropy is also incorporated. This demonstrates that the vibrational contribution to the entropy may be as important as the configurational contribution when considering the inierfacial transformations.