Structural refinement and strengthening of an Fe–Mn–Si–Cr–Ni shape memory alloy by high-speed rolling

The shape recovery under different opposing stress conditions and the various microstructures obtained have been examined following high-speed rolling. An iron-based shape memory alloy that can hardly be rolled at a high strain rate is shown to be capable of being rolled down to 50% of its original thickness by single pass. The shape recovery under the opposing stress applied during reverse transformation is found to increase notably as a result of structural refinement induced by high-speed rolling. In these tests, the specimens were twinned or transformed into hcp and bcc nanophases by the high-speed rolling performed at strain rates as high as ∼104 s−1. The current study emphasizes the contribution of the resultant structural refinement to the strengthening of the shape memory alloy.