Effect of thermomechanical treatment and microstructure on pseudo-elastic behavior of Fe–Mn–Si–Cr–Ni-(V, C) shape memory alloy
Maryam Mohri, Irene Ferretto, Christian Leinenbach, Dohyung Kim, Dimitrios G. Lignos, Elyas Ghafoori
Abstract
This study systematically investigated the effects of heat and thermomechanical treatments on the pseudo-elastic behavior of an Fe-based shape-memory alloy (Fe–17Mn–5Si–10Cr–4Ni-1(V, C) %wt.). First, samples were solution-annealed at 1000 °C for 2 h and aged at 760 °C for 6 h. A thermomechanical treatment was then applied to the heat-treated samples. The microstructure and mechanical properties (i.e., 0.1% yield stress and pseudo-elasticity) were characterized using X-ray diffraction, scanning and transmission electron microscopy, and uniaxial tensile tests. The results showed that decreasing the grain size and precipitation of VCs resulted in an improved pseudo-elasticity. The thermomechanical treatment decreased the number of thermal twins and developed a [111] texture in the austenite phase, which reduced the critical stress for inducing martensite. The presence of VC precipitates and texture formation in the thermomechanical-treated samples increased the pseudo-elastic strain more than twofold from 0.4 to 0.98%.