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 Fe2 8Mn-6Si-5Cr (mass%) shape memory alloy has been observed using atomic force microscopy (AFM). The surface relief of martensites with a preferential or ientation and multi-orientations has been analyzed qualitatively and quanti tatively. When the martensites are produced along a preferential orientatio n, i.e., on one of four {111} shear planes in FCC structure, they are forme d with the so-called "mono-partial" stacking nature, i.e., only a single va riant of martensite is activated. For the case when multi-oriented martensi tes are produced, the relation between the observed martensite plates and t he corresponding motion of a(gamma)/6[112[ Shockley partial dislocations ha ve 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 s ome cases, very thin deformation twin plates (similar to 100nm) and heavily deformed slip bands are observed in the regions of intersection between ma rtensites and they are one of main reasons to produce incomplete shape memo ry effect in Fe-Mn-Si based shape memory alloys.