Ni-Mn-In-Ga条带的马氏体相变和磁热效应的研究

Martensitic Transformation and Magnetocaloric Effect of Ni-Mn-In-Ga Ribbon

采用电弧熔炼和熔体快淬工艺,制备了Ni50Mn33In10Ga7 3~5 mm宽的金属条带。采用X-射线衍射,差示扫描量热分析和磁性测量对材料的相变和磁热效应进行了系统的分析。研究结果表明,该条带在室温下属于立方奥氏体相。随着温度的降低,样品首先经历了从顺磁性奥氏体到铁磁性奥氏体的二级相变,随后是铁磁性奥氏体到弱磁性马氏体的一阶转变。并且观察到马氏体结束温度随磁场的增加逐渐向低温偏移。此外,根据Maxwell方程,计算了样品在马氏体相变及奥氏体居里温度转变的磁熵变。在5T的磁场变化下,同时观察到−4.2 Jkg∙K的负熵变化和3.8 Jkg∙K的正熵变化。

Ni50Mn33In10Ga7 3~5 mm wide metal ribbons were prepared by arc melting and rapid quenching. The phase transitions and magnetocaloric effects in the ribbons were investigated using X-ray diffraction, differential scanning calorimetry, and magnetic measurements. The result indicates that the ribbons exhibit a cubic austenite phase at room temperature. With temperature decreasing, the sample first went through a second-order transition from paramagnetic to ferromagnetic austenite, followed by a first-order transition from ferromagnetic austenite to weak-magnetic martensite. The ending temperature of martensite transition gradually decreased with magnetic fields increasing. In addition, the magnetic entropy changes in the martensite phase transition and the Curie transition of the austenite were both calculated according to Maxwell’s equation. At a field change of 5T, a negative entropy change of −4.2 Jkg∙K and a positive entropy change of 3.8 Jkg∙K were observed simultaneously.