The Bain versus Nishiyama–Wassermann path in the martensitic transformation of Fe

Using atomistic simulations and an embedded-atom interatomic potential, which is capable of describing the martensite (fcc → bcc) transition in Fe, we compare the Bain and Nishiyama–Wassermann transformation paths. We calculate the minimum-energy paths for these two transformations at 0 K. For finite temperature, we study the evolution of the free energy along the two paths, calculated via the method of metric scaling , which shows only small differences. However, the variation of the elements of the stress tensor, and of the atomic volume, show clear differences: the Bain path leads to by a factor of five higher compressive pressures compared to the Nishiyama–Wassermann path. This means that the Bain path requires additional work applied on the system in order to accomplish it, and gives atomistic evidence that the martensite transformation rather follows the Nishiyama–Wassermann path in reality.