Shape memory effect of an antiferromagnetic Mn-9.5Â at.% Fe-5.0Â at.% Cu alloy

This paper mainly presents the shape memory effect in a Mn-rich antiferromagnetic Mn-9.5 at.% Fe-5.0 at.% Cu alloy. The fcc-fct martensitic transformation takes place following an antiferromagnetic transition, and (0 1 1) twin boundaries of fct martensite are formed. When the Ms temperature of the fct martensitic transformation and the Néel point of the antiferromagnetic transition approach each other, a coupling between the second-order antiferromagnetic transition and the first-order martensitic transformation occurs. In this case the thermo-hysteresis of the transformation decreases, or even disappears. The temperature-dependent shape memory effect in the alloy was measured with a dilatometer using pre-compression loading followed by heating (from room temperature to 523 K) and cooling and monitoring the associated shape change. The characteristics of the hysteresis-free or very little thermo-hysteresis property are also discussed in relation to thermodynamic properties.