Interface compatibility-induced quasi-volume-preserving martensitic phase transition in all-d-metal Co2NiT (T = Ti and V) Heusler compounds
Abstract
In this study, the quasi-volume-preserving martensitic phase transition in Co2NiV and Co2NiTi and the physical mechanism were theoretically investigated. Detailed studies revealed that the quasi-volume-conserving martensitic phase transformation originates from the compatible interface between austenite and martensite, which is also responsible for the experimentally observed non- or narrow-thermal-hysteresis phase transition. Consequently, the stressed interface due to incompatible geometric structure gives rise to an irreversible process and induces thermal hysteresis. In Co2NiV and Co2NiTi, the electron relaxation mechanism that drives the volume-conserving martensitic phase transition can be ascribed to lattice distortion and magnetism. As a result of electron relaxation, the interatomic electron-accumulating level was enhanced, which resulted in an increase in the covalent component in interatomic hybridization. The formation of the stronger chemical bonding stabilized the low-symmetric phases in Co2NiV and Co2NiTi. Moreover, the all-d-metal Heusler compounds Co2NiV and Co2NiTi were calculated to be ductile, which enabled them to work under more flexible conditions. Because the martensitic phase transition is metamagnetic, spontaneous magnetostriction can theoretically be expected in Co2NiV and Co2NiTi in a manner similar to that which affects invar alloy. The origin of quasi-volume-conserving martensitic phase transition and its physical mechanism is discussed to assist in the exploration of additional excellent materials for future applications.