Fe-Mn-Si Based Shape Memory Alloys

Abstract

AbstractFe-Mn-Si based alloys are non-thermoelastic shape memory alloys which utilize the stress-induced transformation from γ austenite to ε martensite. After these shape memory alloys are deformed at room temperature, they recover their original shape when heated to 473K or higher. Fe-Mn-Si based alloys contain 15% to 33% Mn, 5% to 6% Si, 0% to 13% Cr, and 0% to 10% Ni in weight. Mn and Si are indispensable for the development of shape memory effect (SME). The amounts of these elements require to be adjusted so that the Neel temperature (TN) lies lower than Ms temperature and the Ms lies just below room temperature. Though the volume of stress-induced martensite is only 20 to 30%, a thermomechanical treatment called “training” has made it possible for the alloy to recover from a tensi le deformation exceeding 3%. Today, the use of the shape memory al loys for steel pipe joints is being studied. They have already been put into practical use for an auxiliary bicycle part to clamp the frame.