Si content dependence on shape memory and tensile properties in Fe–Mn–Si–C alloys

Fe–17Mn–xSi–0.3C alloys (x = 0, 2, 4, 6 mass%) were used to investigate the influence of Si on the tensile properties and the shape recovery strain. We considered three kinds of tensile properties: critical stress for ɛ-martensitic transformation, critical stress for dislocation gliding, and work hardening rate. A significant increase in the shape recovery strain was obtained in the 6%Si added alloy, when the alloys were heated to 873 K after a pre-straining of 8% in tension. The critical stresses for both the ɛ-martensitic transformation and the dislocation gliding increased with an increase in Si content from 0 to 4% but were similar in the 4%Si and 6%Si added alloys. However, the work hardening rate between the 4%Si and 6%Si added alloys was significantly different and was much smaller in the 6%Si added alloy. Hence, a 6%Si addition suppresses the plastic deformation due to the dislocation gliding through the decrease in the work hardening rate along with the solution hardening. As a result, ɛ-martensitic transformation occurs as the predominant deformation mode at smaller strains and improves the shape recovery strain.