Structural effects of high-temperature plastic deformation process on martensite plate morphology in a Fe-Mn-Si-Cr SMA

An Fe–Mn–Si–Cr shape memory alloy (SMA) was induction melted, in a cold crucible furnace, cast into cylindrical moulds and swaged by means of two hot working processes. From repeatedly hot forged and hot rolled billets, different specimens were prepared with longitudinal and transversal orientations with respect to main plastic deformation direction. After corresponding metallographic preparation, structural analyses comprising optical (OM), scanning electron (SEM) and atomic force (AFM) microscopy observations were performed with the aim to emphasise the structural effects, of the two above mentioned plastic deformation processes on martensite plate morphology, size and distribution. The paper reports the results recorded by OM, SEM and AFM and corroborates martensite plate surface relief with high–temperature plastic deformation process. The results show that martensite plates were shorter and deeper in hot forged specimens as compared to hot rolled ones, an effect which is atypical for Fe–Mn–Si–Cr SMAs.