织构取向Ni_(54)Mn_(21)Ga_(25)合金的相变和磁致应变

Phase Transition and Magnetic-Field-Induced Strain in Textured Ni_(54)Mn_(21)Ga_(25) Polycrystalline Alloys

用定向凝固方法制备Ni54Mn21Ga25取向多晶合金。在292K下测量了样品的磁致伸缩应变回线,结果表明:加正反方向磁场时,磁致伸缩应变回线基本对称,并存在磁致伸缩跳跃现象,饱和磁致应变约为-1.06×10-3,对应的饱和磁场为0.4T。差示扫描量热仪测量显示,马氏体相变起始温度Ms为334K,结束温度Mf为320K;逆马氏体相变起始温度As为333K,结束温度Af为353K。阻温特性测量给出样品的居里温度约350K左右。

The Ni54Mn21Ga25 polycrystalline alloys were prepared by unidirectional solidification in a water-cooled copper crucible in the vacuum arc furnace.The microstructures and stoichiometries of the alloy were characterized with X-ray diffraction and energy dispersive spectroscopy.The magnetic-field-induced strain （MFIS） loop was evaluated at 292 K.The results show that MFIS loop looks basically symmetric at an external magnetic field varied at opposite directions,and that abrupt jumps on both sides of the loop can be observed.The saturated MFIS was found to be approximately-1.06×10^-3,corresponding to a field of 0.4 T.The differential scanning calorimetric （DSC） measurements indicate that the initial Martensitic transition starts at 334 K,and ends at 320 K,whereas the starting and ending temperatures in the reverse Martensitic transition are 333 and 353 K,respectively.The thermal resistance characteristics show that Curie temperature,T_c,is about 350 K.