W. Peng, F. Cai, X. Yang, A. Zhang, M. Yan, H. Zou, Nanchang University, Nanchang, China; X. Wang, Arizona State University, Tempe, AZ; J. Zhang, Shanghai Jiao Tong University, Shanghai, China
A Mn-based alloy undergoes antiferromagnetic transition and FCC-FCT martensitic transformation. High damping, magnetic field induced shape memory effect and temperature controlled narrow two-way shape memory effect are found in the alloy and the mechanism of these performances is related to their twin microstructure. Such twin microstructure is investigated with transmission electron microscopy (TEM) and the observed lamella-like microstructure is determined as twins with selected area electron diffraction. In-situ heating in TEM makes the contrast of morphology of twins weaker, and then totally disappears until the temperature above Af and TN. During the low temperature intervals, the martensitic twins are reversibly mobile, which can duplicate the morphology of the different temperatures. When the alloy was cooled from higher temperature, the tweed-like microstructures induced by antiferromagnetic transition, by which the sites and orientations of the original twins changed. The solutions of Landau free energy equation indicates that the morphology of martensitic twins was affected by antiferromagnetic transition when it is cooled from the temperature above TN.
