Quantitative study of surface relief produced by martensitic transformation in Fe-Mn-Si-Cr shape memory alloy using atomic force microscopy

Surface relief produced by stress-induced martensitic transformation in Fe28Mn-6Si-5Cr (mass%) shape memory alloy has been observed using atomic force microscopy (AFM). The surface relief of martensites with a preferential orientation and multi-orientations has been analyzed qualitatively and quantitatively. When the martensites are produced along a preferential orientation, i.e., on one of four {111} shear planes in FCC structure, they are formed with the so-called "mono-partial" stacking nature, i.e., only a single variant of martensite is activated. For the case when multi-oriented martensites are produced, the relation between the observed martensite plates and the corresponding motion of a(gamma)/6[112[ Shockley partial dislocations have been obtained. The result indicates that only a single variant on each {111} close-packed plane is activated even in such a case. In addition, in some cases, very thin deformation twin plates (similar to 100nm) and heavily deformed slip bands are observed in the regions of intersection between martensites and they are one of main reasons to produce incomplete shape memory effect in Fe-Mn-Si based shape memory alloys.