磁制冷材料Ni-Mn-Ga合金的相变与奇异热膨胀特性  

Martensitic transformation and abnormal thermal expansion in Ni-Mn-Ga alloy magnetic refrigeration materials

作　　者：魏生贤 李会[2] 李哲 何禧佳 张元磊 时有明[2] 陶昌[2] Wei Shengxian;Li Hui;Li Zhe;He Xijia;Zhang Yuanlei;Shi Youming;Tao Chang(Center for Magnetic Materials and Devices, Qujing Normal University, Qujing 655011, China;College of Physics and Electronic Engineering, Qujing Normal University, Qujing 655011, China)

机构地区：[1]曲靖师范学院磁性材料及器件研究中心,曲靖655011 [2]曲靖师范学院物理与电子工程学院,曲靖655011

出　　处：《农业工程学报》2018年第10期85-91,共7页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金项目(31760341;51661029);云南省地方本科高校联合专项-面上项目(2017FH001-054);2017年地方高校国家级大学生创新创业训练计划项目(201710684007)

摘　　要：Ni-Mn-Ga合金是典型的磁制冷材料,其热膨胀系数是工程设计中最重要的参数之一。为深入研究Ni-Mn-Ga合金的热膨胀特性,该文利用SEM、XRD、DSC及PPMS系统分别对合金Ni_(54+x)Mn_(19–x)Ga_(27)(x=0、0.2、0.4、0.6)的组分、结构、相变温度、磁结构转变及热膨胀特性进行试验测试。结果表明,随着Ni含量的增加,Ni_(54+x)Mn_(19–x)Ga_(27)合金的马氏体相变温度逐渐升高。当x从0.0增至0.6时,正反马氏体相变峰温TM与TA分别从257、265 K增至292、299 K。零场热应变曲线表明,Ni-Mn-Ga合金具有各向同性的热膨胀特性。马氏体相与奥氏体相的热膨胀系数分别位于8.87~16.60×10–6/K与5.21~6.26×10–6/K之间。而在马氏体相变附近,合金出现了奇异的、明显的负热膨胀行为,且升、降温过程合金的负热膨胀系数分别位于–147.54~–17.60×10–6/K与–133.30~–88.72×10–6/K之间,分别约为马氏体相的1.47~16.63倍与6.63~12.89倍。这种奇异的负热膨胀行为很可能是由于马氏体变体的成核、重取向所引起的。研究结果对磁制冷材料Ni-Mn-Ga合金热膨胀系数的调控及其工程应用具有较好的指导意义。Ni-Mn-Ga alloy is a kind of typical magnetic refrigeration material. The thermal expansion coefficient of the alloy is one of the most important parameters in the engineering design. The mismatch of thermal expansion coefficient between the various materials used in magnetic refrigerators can lead to thermal stresses that can trigger complex failure mechanisms like component distortion, stress rupture, and thermomechanical fatigue, and thereby seriously degrade device reliability and lifetime. Therefore, minimizing the mismatch between the materials is desirable if for no other reason than to significantly improve overall device reliability. In this work, the magnetic refrigeration materials Ni54＋xMn19-xGa27（x=0, 0.2, 0.4, 0.6） with nominal composition were fabricated by conventional arc melting in an argon atmosphere using high purity elements Ni （99.98%）, Mn （99.98%） and Ga （99.999%） to reveal the thermal expansion properties of Ni-Mn-Ga alloy. The actual compositions, crystal structures, martensitic transformation temperatures, magnetic transition and zero field thermal strain of the alloys were experimentally investigated by a scanning electron microscope equipped with an energy-dispersive spectrometer （SEM-EDS）, an x-ray diffractometer （XRD）, a differential scanning calorimetry （DSC）, a vibrating sample magnetometer （VSM） and a standard strain-gauge connected with physical properties measurement system （PPMS）. The room temperature XRD patterns of Ni54＋xMn19-xGa27indicate that the alloys （x≤0.4） possess an ordered L21（cubic） austenite structure and the sample （x=0.6） predominately possesses a 7M modulated martensitic structure with small residual traces of non-modulated martensitic structure. The results from DSC and magnetic transition measurements show that the martensitic transformation temperatures gradually increase with the Ni content increasing. Moreover, the peak temperatures of direct and reverse martensitic transformations increase from 257, 266

关 键 词：制冷 磁性材料 相变 NI-MN-GA合金 热膨胀特性 负热膨胀行为 

分 类 号：TK519[动力工程及工程热物理—热能工程]