| In the Cu-Mn-Al Heusler alloy ternary system the martensitic transformation may proceed in solid solutions having concentration nonuniformities related to small coherent particles forming during the degradation of the high temperature phase and having no spontaneous martensitic transformation on cooling. These particles may have a size well below the critical size of martensite nucleation. In the present work we study the temperature dependence of the structure and magnetic properties of Cu-Mn-Al in the temperature interval including the phase transition. Forward (cooling) and reverse (heating) structural transformations were studied directly by optical microscopy and illustrated by movies showing the motion and transformation pathways of multiple martensite interfaces. Simultaneous temperature measurements of the AC magnetic susceptibility gave a possibility to estimate the volume changes of high- and low-temperature phases during the transformation necessary for modelling the behaviour of this type of alloys. |
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