Thermomechanical Characterization and Performance Evaluation of an Fe-Based Shape Memory Alloy for Coupling Applications

This study investigates the thermomechanical behavior and performance of a Fe-based shape memory alloy (Fe-SMA) for coupling applications. The alloy, composed of Fe–17Mn–5Si–10Cr–4Ni–1(V,C) (wt.%), was manufactured via induction melting followed by hot rolling. To evaluate its mechanical properties and shape memory effect (SME), dogbone-shaped specimens were extracted from the rolling and transverse directions of 50 mm diameter rods. The microstructural analysis of extracted samples in rolling direction reveals that samples extracted from the outer region of rod exhibited finer grains compared to those taken from the core. A two-step heat treatment was applied to enhance phase transformation characteristics, resulting in the formation of fine (Cr,V)-carbides. All as-received and heat-treated samples were subjected to tensile testing, pre-straining, and thermal activation under varying constraint conditions. Mechanical testing revealed improved strength and superelasticity (SE) in heat-treated samples, particularly in the rolling direction, with notable dependence on grain size and carbide distribution. Recovery strain and stress were characterized under free and constrained conditions, simulating coupling behavior. Under partial restraint conditions, it was observed that constraining samples at higher temperatures during activation up to 200 °C led to enhanced recovery strains but resulted in reduced recovery stresses. The results demonstrate the feasibility of tailoring Fe-SMA behavior for structural coupler applications through thermomechanical processing and activation strategies.