Effect of texture heterogeneities on the shape memory properties of rolled Fe-Mn-Si SMA

We have investigated an Fe-30Mn-4Si shape memory alloy to clarify the effect, on the bulk texture, of the shear layers resulting from two different thermo-mechanical treatments. XR analysis has shown the existence of texture heterogeneity through the rolled sheet's thickness, due to the effect of friction between sheet and rolls. Neutron diffraction revealed that textured layers on the sheet's surface affect the whole volume. The texture found on the surface of the sheet rolled at 600 degrees C is the most favourable for the gamma ->epsilon martensitic transformation which is the origin of the shape memory effect. Comparing these results with those obtained on sheets rolled at room temperature, we found that shear deformation gradients produce changes in the bulk material texture. Tensile tests initially induce the martensitic transformation in those grains favourably oriented. As a result, these favourable orientations disappear in the remnant austenite.