Twinning of deformation-induced ε-martensite in Fe-30Mn-6Si shape memory alloy

The epsilon-martensite, which is induced by tensile plastic deformation, twins under further plastic deformation due to the collision of different habit plane variants. Crystallographic characteristics of the mechanical epsilon twins were examined in this study by electron backscattering diffraction in a Fe-30Mn-6Si shape memory alloy, which was subjected to tensile deformation of up to 10% at room temperature. epsilon twins of (10 (1) over bar2} and (10 (1) over bar1) types were observed at the intersections of two different habit plane variants. Non-basal shearing forces on the pre-existing epsilon-martensite in the directions perpendicular to or 30 degrees-inclined from the intersection axis (Type I and II) are responsible for the (10 (1) over bar2} and (10 (1) over bar1) epsilon twins, respectively. The former twins at Type I intersections exhibited a self-accommodating microstructure consisted of different twinning-plane variants. The occurrence of the (10 (1) over bar1) twinning at Type II intersections suggests an inclined twinning shear mechanism. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.