快速凝固超细晶纤维的制备及磁热特性研究

Ni-Mn-Ga alloy shows the excellent magnetocaloric properties due to their structure transition near room temperature, thus obtaining lots of interestings in magnetic refrigeration. However, the magnetic hysteresis loss resulting from the phase transformation hysteresis has been limited the magnetic refrigeration applications of Ni-Mn-Ga alloy. Hence, this project utilized melt-extracted method for fabricating microwires with ultra-fine grains, and the performances of Ni-Mn-Ga alloy are improved by the grain refining and the fourth element, such as reducing magnetic hysteresis loss, broadening the phase transition range and adjusting the magnetocaloric effects. The research mainly includes “hysteresis loss dependence on the grain size of the wires”, “mechanism of Fe-doping influencing on the positive and inverse magnetocaloric effect” and “composites with multi-compositions broadening the working range”. We hope to clarify the mechanism of small-sized effect and ultra-fine grain influencing on hysteresis loss, reveal the law of magnetic field of magnetic structure coupling and show the compositional dependence of the positive and inverse magnetocaloric effect. The above mentioned researches focus on solving the key problems including high driving field, large hysteresis loss and narrow working temperature range in magnetic refrigeration, thus promoting the practical applications of Ni-Mn-Ga-Fe ultra-fine wires with high strength and ductility, less magnetic hysteresis loss and excellent magnetocaloric effect.

Ni-Mn-Ga合金因其近室温结构相变致优异磁热性能，已成为近年来磁制冷材料研究热点，但其相变滞后所导致的磁滞损耗限制了其应用。本项目利用快速凝固熔体抽拉技术制备具有超细晶结构Ni-Mn-Ga-Fe纤维，从细化晶粒和第四组元改性的角度优化Ni-Mn-Ga合金性能，降低磁滞损耗，拓宽马氏体相变窗口及阐述正、逆磁热效应产生机理，基本内容包括“纤维磁滞损耗的尺寸依赖性”、“Fe掺杂对正、逆磁热效应的调控机理”和“多成分纤维复合拓宽磁制冷工作区间”等。阐明小尺寸效应和晶粒超细化对磁滞损耗的作用机制，揭示磁场对磁结构耦合的规律，明晰正、逆磁热效应的成分依赖性，以期解决磁制冷中高驱动场、大磁滞损耗及磁制冷工作区间窄等瓶颈问题，这种具有高强度、延展性、小磁滞损耗及优异磁热性能Ni-Mn-Ga-Fe超细晶纤维，有望成为一种新型磁制冷工质，也为磁制冷的实际应用提供基本思路。

Ni-Mn-Ga合金因其近室温结构相变致优异磁热性能，已成为近年来磁制冷材料研究热点，但其相变滞后所导致的磁滞损耗限制了其应用。本项目采用快速凝固熔体抽拉液态成形技术制备Fe掺杂Ni-Mn-Ga超细晶结构的微丝，着眼于细化晶粒和第四组元改性的角度优化Ni-Mn-Ga合金性能，项目取得了如下结果：制备了超细晶结构合金纤维，降低了磁滞损耗，拓宽了马氏体相变窗口及阐述了正、逆磁热效应产生机理，阐明了小尺寸效应和晶粒超细化对磁滞损耗的作用机制，揭示了磁场对磁结构耦合的作用规律，明晰了正、逆磁热效应的成分依赖性，解决了磁制冷中高驱动场、大磁滞损耗及磁制冷工作区间窄等瓶颈问题。这种具有高强度、延展性、小磁滞损耗及优异磁热性能Ni-Mn-Ga-Fe超细晶纤维，有望成为一种新型磁制冷工质。