Composition and electron concentration dependence of transformation temperature in Ni2＋x＋y Mn1-xGa1-y, Ni2＋x Mn1-x Ga alloys with first order magnetic transition were studied. For Ni2 ＋ x ＋ y Mn1- x Ga1-y alloys,...Composition and electron concentration dependence of transformation temperature in Ni2＋x＋y Mn1-xGa1-y, Ni2＋x Mn1-x Ga alloys with first order magnetic transition were studied. For Ni2 ＋ x ＋ y Mn1- x Ga1-y alloys, martensitic transformation temperature TM increases and Curie temperature Tc decreases with the increase of electron concentration e/a, they intercept at e/a = 7.68. TM and Tc decrease when continue to increase electron concentration. While for Ni2＋x Mn1-xGa alloys, they cross at e/a = 7. 635. Before their crossing, the change tendency with e/a is the same as Ni2＋x＋yMn1-xGa1-y alloys;, after their crossing, both TM and Tc increase slowly. The different relations between TM and Tc and e/a within two NiMnGa alloys show that TM and Tc depend not only on e/a, but also on composition.展开更多
Microstructure,phase transformation and mechanical properties of NiMnGa particles/Cu composites prepared by spark plasma sintering method were investigated by SEM,EDS,XRD,susceptibility measurements and mechanical tes...Microstructure,phase transformation and mechanical properties of NiMnGa particles/Cu composites prepared by spark plasma sintering method were investigated by SEM,EDS,XRD,susceptibility measurements and mechanical tests.The NiMnGa particles were found to react with Cu matrix and the composites exhibited a similar crystal structure to the Cu matrix.The martensitic transformation and Curie transition of the composites were weakened due to the composition change of NiMnGa particles caused by reactions.With increasing NiMnGa particles content,the martensitic transformation and Curie transition of the composites were enhanced to some extent.However,the martensitic transformation temperature and Curie transition temperature were decreased by~50 K as compared to those of the original NiMnGa particles.The compressive strength of the composites increased with the increase of NiMnGa particles content,whereas the compressive strain was decreased gradually.展开更多
Giant magnetic field induced strain （MFIS） up to 6.2% is achieved in the Ni50Mn27.5Ga22.5 single crystals with 5 M martensitic structure at room temperature. The switching magnetic field was about 2.4 kOe for the ma...Giant magnetic field induced strain （MFIS） up to 6.2% is achieved in the Ni50Mn27.5Ga22.5 single crystals with 5 M martensitic structure at room temperature. The switching magnetic field was about 2.4 kOe for the magnetostrain. A ‘magnetization jump＇ effect in the switching field applied along the initially hard direction confirms the occurrence of the large magnetostrain. The temperature dependence of the magnetostrain is investigated in lower temperature range. A linear decrease of the magnetostrain is observed with increasing temperature, but a strong decrease is monitored near the reverse martensitic transformation temperature.展开更多
文摘Composition and electron concentration dependence of transformation temperature in Ni2＋x＋y Mn1-xGa1-y, Ni2＋x Mn1-x Ga alloys with first order magnetic transition were studied. For Ni2 ＋ x ＋ y Mn1- x Ga1-y alloys, martensitic transformation temperature TM increases and Curie temperature Tc decreases with the increase of electron concentration e/a, they intercept at e/a = 7.68. TM and Tc decrease when continue to increase electron concentration. While for Ni2＋x Mn1-xGa alloys, they cross at e/a = 7. 635. Before their crossing, the change tendency with e/a is the same as Ni2＋x＋yMn1-xGa1-y alloys;, after their crossing, both TM and Tc increase slowly. The different relations between TM and Tc and e/a within two NiMnGa alloys show that TM and Tc depend not only on e/a, but also on composition.
基金supported by the National Natural Science Foundation of China(No.51201044)High-level Scientific Research Guidance Project of Harbin Engineering University,China(No.3072022TS1006)+1 种基金Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province,China(No.LBH-Q16046)Key Laboratory of Superlight Materials&Surface Technology(Harbin Engineering University),Ministry of Education,China.
文摘Microstructure,phase transformation and mechanical properties of NiMnGa particles/Cu composites prepared by spark plasma sintering method were investigated by SEM,EDS,XRD,susceptibility measurements and mechanical tests.The NiMnGa particles were found to react with Cu matrix and the composites exhibited a similar crystal structure to the Cu matrix.The martensitic transformation and Curie transition of the composites were weakened due to the composition change of NiMnGa particles caused by reactions.With increasing NiMnGa particles content,the martensitic transformation and Curie transition of the composites were enhanced to some extent.However,the martensitic transformation temperature and Curie transition temperature were decreased by~50 K as compared to those of the original NiMnGa particles.The compressive strength of the composites increased with the increase of NiMnGa particles content,whereas the compressive strain was decreased gradually.
基金Supported by the National Natural Science Foundation of China under Grant No 50271002, and the New Century Programme for Excellent Talents of the Ministry of Education of China under Grant No 04-0165.
文摘Giant magnetic field induced strain （MFIS） up to 6.2% is achieved in the Ni50Mn27.5Ga22.5 single crystals with 5 M martensitic structure at room temperature. The switching magnetic field was about 2.4 kOe for the magnetostrain. A ‘magnetization jump＇ effect in the switching field applied along the initially hard direction confirms the occurrence of the large magnetostrain. The temperature dependence of the magnetostrain is investigated in lower temperature range. A linear decrease of the magnetostrain is observed with increasing temperature, but a strong decrease is monitored near the reverse martensitic transformation temperature.
