A chemical-structural model for coherent martensite/parent interface in Mn-based antiferromagnetic shape memory alloys.

The martensite/parent coherent interface of Mn-based shape memory alloys (SMAs) is a significant part in the research of their martensitic transformation, reversible shape memory effect and magnetic shape memory effect. In the present work, a chemical-structural model was proposed to calculate the martensite/parent coherent interfacial energy of Mn-X (X = Cu, Fe) alloys. In this model, the coherent heterophase interfacial energy consists of chemical and structural parts. Resulting from the formation process of the heterophase interface, the chemical interfacial energy is expressed as the incremental value of bond energy, while the structural part is obtained by calculating the interfacial strain energy. The results show that the structural interfacial energy plays the chief role in the total interfacial energy, and the total interfacial energy decreases as the temperature rises when the alloy composition is fixed. In addition, the preferred orientation has noteworthy influence on the total interfacial energy. Using the proposed model, interfacial energy, interfacial entropy, interfacial enthalpy and interfacial heat capacity are found to be correlated with temperature and interface preferred orientation. Furthermore, the influences of alloy composition, modulus softening, and the index of the habit plane on the results were discussed.