In-situ phase transformation studies of Ni48Mn39In13 melt-spun ribbons

The phase transformation in Ni48Mn39In13 melt-spun ribbons has been studied by employing in-situ transmission electron microscopy (TEM) techniques. At room temperature, the investigations showed the martensite phase consisting of plates with internal stacking faults. This phase exhibited the presence of 7M and 5M modulations. In addition, a small volume fraction of the austenite phase was observed. Upon in-situ heating from room temperature to 95 °C, the martensite phase transformed to austenite phase. However, in the subsequent cooling–heating cycles, the martensite phase was retained at high temperature. We discuss our experimental observations and the possible mechanisms for the stabilization of the martensite phase due to thermal cycling.

► TEM studies on Ni48Mn39In13 melt-spun ribbon revealed the presence of 7M and 5M modulated martensite structures at RT.
► A small volume fraction of austenite phase was also observed in relatively fine grains (∼3 μm) at RT.
► Martensite to austenite phase transformation was observed upon in-situ heating. The austenite phase displayed ordered L21 structure.
► The martensite phase was retained at high temperature upon thermal which has been attributed to the grain size effect, dislocations and atomic disorder.