Investigation of the energetics of structural transformations in Co-based binary alloys

Abstract

The energy pathways associated with the martensitic transformation in shape memory alloys (SMA's), though the focus of extensive research over the past decades, are still unclear. In this work we build a framework using an energetics approach to describe the martensitic f.c.c-h.c.p transformation in Co-based alloys and to investigate the effect of alloying on the transformation First principle calculations are used to determine the energy landscape of the transformation using the Shoji - Nishiyama and Wentzcovitch - Lam models in Co - (Al, Fe, Si) binary alloys over a range of composition. The martensitic transformation is an energy barrier crossing event and exhibits concomitant reduction in symmetry. Hence a steepest descent optimization technique is employed to realize the minimum energy path and the transition states of the transformations over the energy landscape. The energy barriers as a function of composition are calculated and compared against available experimental data.