Abstract
The effect of chemical composition and thermomechanical treatments on both the mechanical properties and the shape memory (SM) capacity of Fe-based SM alloys was investigated by X-ray diffraction and optical and transmission-electron microscopy analysis. We produced the Fe-17Mn-6Si-10Cr-5Ni and Fe-22Mn-3Si-10Cr-5Ni alloys (17Mn and 22Mn, respectively) and measured the degree of shape recovery (DSR) after tension and bending for samples rolled and annealed in different conditions. We found that the 17Mn alloy rolled at 1000 °C and annealed at 700 °C had the highest DSR, i.e. 78%. After tension, the microstructure contained nanometre sized stress-induced ε-martensite plates in a matrix composed of dislocations, SFs and precipitates. On the other hand, after tensile deformation, the dislocation density observed in the 22Mn sample rolled at 1000 °C and annealed at 700 °C was higher than before tension. This alloy's low 48% DSR is a consequence of permanent, nonrecoverable plastic deformation.
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