Importance of Shear in the bcc-to-hcp Transformation in Iron
Iron shows a pressure-induced martensitic phase transformation from the ground state ferromagnetic bcc phase to a nonmagnetic hcp phase at ≈13 GPa. The exact transformation pressure (TP) and pathway are not known. Here we present a multiscale model containing a quantum-mechanics-based multiwell energy function accounting for the bcc and hcp phases of Fe and a construction of kinematically compatible and equilibrated mixed phases. This model suggests that shear stresses have a significant influence on the bcc↔hcp transformation. In particular, the presence of modest shear accounts for the scatter in measured TPs. The formation of mixed phases also provides an explanation for the observed hysteresis in TP.
© 2004 American Physical Society. (Received 16 March 2004; published 10 September 2004) Support from the DOE through Caltech's ASCI/ASAP Center for the Simulation of the Dynamic Response of Materials and from the Office of Naval Research is gratefully acknowledged. Dr. Matt Fago is the primary author of the lamination code employed in this work.
Published - CaspersenLewOrtizCarter2004.pdf