Nanoscale twinning and superstructures of martensite in the Fe–Mn–Al–Ni system

Fe–Mn–Al–Ni-based shape memory alloys are regarded as promising shape memory materials, which can be utilized due to its pseudoelastic properties in a wide field of applications. Based on a detailed microstructural analysis, it is demonstrated that the formation of different austenitic superstructures and their impact on the resulting structure of the martensite tremendously affect the reversibility of the martensitic transformation. In addition to the usually investigated chemical compositions, which produce a nanoscopic A2 + B2 austenitic state, Mn-rich Fe–Mn–Al–Ni alloys, relying on a fully ordered D03/L21 austenite, may be suggested to constitute a potentially new group of SMAs in the Fe–Mn–Al–Ni system.