热空位调控MnCoGe基合金马氏体相变机理研究

六角MM'X合金是一类新的磁相变材料，具有高可调的巨磁热效应，在磁制冷、热磁发电、磁存储等方面具有潜在应用优势。研究表明，分级淬火和循环时效热处理（不同的淬火温度、不同的时效温度、不同的时效时间）产生的潜在热空位能够有效调控MnCoGe基合金的马氏体相变，可在确定成分的合金中获得不同的磁/结构物态，是一种调节磁相变行为及物性的有效自由度。本申请项目拟通过正电子湮灭技术证明热空位存在并定量测量热空位浓度，研究热空位对晶体结构、磁性和相稳定性及其他物性影响，揭示热空位调控马氏体相变的机理，深化热空位对马氏体相变作用规律的认识。同时为新的MnCoGe基磁相变合金的发现提供研究依据和调控方法，具有重要的科学和实践意义。

Hexagonal MM'X alloys, as a new class of magnetostructural transition materials with highly adjustable giant magnetocaloric effect, potential application advantages in fields of magnetic refrigeration, thermomagnetic power generation and magnetic storage and so on. The study shows that potential thermal vacancies obtained through staged quenching and cyclical ageing (different quenching temperature, ageing temperature and ageing time) can effectively tailor magnetostructural transitions of MnCoGe-based alloys, different magnetic/structural states in determined alloy composition can be gained. Therefore, thermal vacancy becomes an effective degree of freedom to tailor magnetostructural transition behavior and physical properties. In order to study the influence of the thermal vacancy on the crystal structure, magnetism, phase stability and other physical properties, reveal the mechanism and understand deeply the regulation of tuning martensitic transformation, the present proposal aims to prove the existence of thermal vacancy and quantitatively measure the thermal vacancy concentration by positron annihilation technique (PAT). At the same time, the current proposal has important significance in scientific researches and technological applications for the discovery of new MnCoGe-based magnetostructural transition alloys.