Study of 10M' Nanotwinned Phase in the Vicinity of Martensitic Transformation in Ni-Mn-Ga Magnetic Shape Memory Alloy

Abstract

Ni50.0Mn28.5Ga21.5 single crystal exhibiting magnetic shape memory effect was analysed by X-ray diffraction, electric resistivity and differential scanning calorimetry. Based on the intensities of the measured diffraction peaks, we discuss the evolution of the structure and microstructure during heating and cooling. Electric resistivity and DSC curves detect anomalous behaviour prior the transformation from martensite to austenite. We ascribe these pre-transformation changes in measured curves to formation of the recently discovered nanotwinned form of 10M martensite.

Hysteretic structural changes within five-layered modulated 10M martensite of Ni–Mn–Ga(–Fe)

“…In the incommensurate 10M phase, we observed only one reflection (400) , instead of two: (400) and (040), due to the refinement of the a/b twins. Such refinement has already been observed and discussed in [51,75]. For higher-temperature commensurate phase, the (400) and (040) reflections were clearly distinguished, indicating the relatively large a/b twin domains and thus well separated a/b twin boundaries.…”