Role of the Surface in Solid-Solid Phase Transitions: Molecular Dynamics Study of the alpha-gamma Transition in Fe

BJ Wang and HM Urbassek, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 47A, 2471-2480 (2016).

DOI: 10.1007/s11661-016-3370-5

Using classical molecular dynamics simulation, we study the role of surfaces on solid-solid phase transformations. We contrast the transformation behavior of a thin film (two free surfaces) with a bulk system and with a system containing only one free surface. We focus on bcc Fe and induce the transformation from the bcc to the fcc phase by applying biaxial strain. We find that the critical strain at which the material transforms is independent of whether the system has a free surface or not. However, the nucleation mechanism of the new phase and also the transformation speed are strongly influenced by the existence of surfaces. While bulk systems fail early (after phase transformation to a polycrystal) under the applied load, systems with a free surface show a considerably higher ductility. (C) The Minerals, Metals & Materials Society and ASM International 2016

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