Transformation lines in an Fe-based shape memory alloy under tensile and compressive stress states

Uniaxial transformation/deformation behavior of an Fe-based shape memory alloy is investigated under tensile and compressive stress state through the transformation start/finish conditions, which can be drawn as the straight lines on the stress—temperature plane. The martensite start stresses in tension and compression form the straight lines, which are, however, not symmetric with respect to the stress. In both tension and compression, and austenite start and finish lines shift from an initial austenite line to the lower temperature side and the higher temperature side, respectively, meaning the reverse transformation zone becomes wider, as the extent of prior martensitic transformation increases. The slope of the austenite lines does not change in this process. The austenite start/finish lines in tension are extended to the compression side without change in slope. The same is true for the austenite start/finish lines in compression. iaxial thermomechanical hystereses, the stress—strain—temperature loops can be well explained by means of the transformation lines determined.