Continuous Transition of Deformation Mode in Fe-30Mn-5Si-1Al Alloy

Deformation modes at various stages of plastic deformation have been investigated at identical locations in an Fe-30Mn-5Si-1Al (mass%) alloy specimen, which exhibits a good shape memory effect associated with FCC (gamma)-> HCP (epsilon) martensitic transformation and relatively high ductility caused by deformation twinning. The surface relief caused by gamma ->epsilon martensitic transformation, deformation twinning and slip band formation has been analyzed by measuring surface tilt angles corresponding to each deformation mode by atomic force microscopy. Although epsilon-martensitic transformation is the dominant deformation mode in the early deformation stage, a part of the epsilon-martensite plates changes to deformation twins with the increase of deformation volume. Slip deformation also occurs inside the same region under excessive strain. The continuous transition of these deformation modes also occurs in the other grains in the same order: epsilon martensite -> deformation twins-slip bands.