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摘要
Ni-Mn based alloys have potential applications in magnetic actuators, sensors, solid state magnetic refrigeration, negative thermal expansion materials and other fields. The narrow phase transition temperature span restricts the practical application of Ni-Mn based alloys. The structure, phase transition properties and hydrostatic pressure dependence of phase transition temperature and phase transition temperature span were investigated experimentally in Ni55.5Mn18Ga26.5 alloy to broaden the temperature span of phase transition. The results show that the alloy sample crystallizes in a tetragonal martensite structure at room temperature and the martensitic transformation temperatures are higher than room temperature. All the martensitic transformation temperatures and the transformation temperature span increase gradually with the increase of hydrostatic pressure. Importantly, the average sensitivity of phase transition peak temperature and phase transition temperature span to hydrostatic pressure are about 29.35, 25.88, 42.11 and 39.46 K/GPa, respectively, during the direct and reverse martensitic transformation. It is obvious that the application of hydrostatic pressure is not only beneficial to drive the martensitic transformation, but also helpful to broaden the transformation temperature span in Ni-Mn-Ga alloy. These findings are very meaningful to adjust the phase transition temperature and the broadening of phase transition temperature span in Ni-Mn-Ga alloy system.
