ABSTRACT

The MnNiFeGe alloy is prepared by high-pressure annealing method. It is found that the martensitic transformation temperature after high-pressure annealing of this alloy decreases with the increasing thermal hysteresis. Besides, another magnetic phase transition above the martensitic transformation is observed, which is due to the existence of a large amount of retained austenite induced by high-pressure annealing. As a result, this alloy shows two positive magnetic entropy change peaks, corresponding to the ferromagnetic phase transition of the austenite and the magnetic martensitic transformation, respectively. The magnetic phase transitions, the variable-temperature crystal-structure evolution, and the magnetocaloric properties of this alloy are investigated in detail.

摘要

MnNiFeGe合金是通过高压退火法制备的。发现该合金在高压退火后的马氏体转变温度随着热滞的增加而降低。此外，观察到在马氏体相变之上的另一磁相变，这是由于存在高压退火引起的大量残余奥氏体的存在。结果，该合金显示出两个正的磁熵变峰，分别对应于奥氏体的铁磁相变和磁马氏体转变。详细研究了该合金的磁性相变，变温晶体结构演变和磁热性能。