采用光学显微镜、扫描电子显微镜、X射线衍射仪、差示扫描量热仪和显微硬度计等测试手段,研究了Fe含量对Ni 50-x/2 Ti 50_(x/2) Fe_(x)(x=0.5%~3.5%)形状记忆合金微观组织、相变行为和显微硬度的影响规律.结果表明:NiTiFe三元形状记忆...采用光学显微镜、扫描电子显微镜、X射线衍射仪、差示扫描量热仪和显微硬度计等测试手段,研究了Fe含量对Ni 50-x/2 Ti 50_(x/2) Fe_(x)(x=0.5%~3.5%)形状记忆合金微观组织、相变行为和显微硬度的影响规律.结果表明:NiTiFe三元形状记忆合金组织主要由Ni 4.8 Ti 5Fe 0.2相、Ni 3Ti相和基体组成,随着Fe含量的增加,合金组织中等轴晶粒尺寸逐渐增大;合金的相变温度,随Fe含量的增加迅速下降;合金的显微硬度随Fe含量的增加而急剧增加,与Fe含量呈正相关关系,当x=3.5%时达到最大值469.91 HV.展开更多
Ferromagnetic shape memory alloys （FSMAs） such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% 9% due to the variant rearrangement. ...Ferromagnetic shape memory alloys （FSMAs） such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% 9% due to the variant rearrangement. Recently, the present authors have reported that in the Ni-Ga-Fe alloy the martensitic transformationfrom the B2 and/or the L21 structures into a seven-layer or five-layer modulated structure occurs upon cooling. In this alloy system, however, it is impossible to obtain a martensite phase at RT with a Curie temperature （TC） higher than 100 ℃. In this work,the effects of substitution of Co for Ni on the martensitic and magnetic transformations,crystal structures and phase equilibria in Ni-Ga-Fe alloys were studied.Ni-Ga-Fe-Co alloys were prepared by induction melting under an argon atmosphere.Small pieces of specimens were taken from the ingot and homogenized at 1433 K for 24 h followed by quenching in water. The obtained specimens were aged at 773 K for 24 h and then quenched. The compositions of each phase were determined by energy dispersion X-ray spectroscopy （EDX）. The martensitic transformation temperatures and TC were measured by differential scanning calorimetry （DSC） and vibrating sample magnetometer （VSM） measurement. The crystal structure of martensite phase was observed by X-ray diffractmeter （XRD） and transmission electron microscope （TEM）.The Curie temperature TC was increased with increasing Co content while the martensitic transformation temperature slightly decreased. In the Ni<sup>54-x Ga<sup>27 Fe<sup>19 Cox ,TC increases from 303 K to 408 K with increasing Co content from x=0 to x=6. The crystal structure of the martensite phase and the phase equiribria in the Ni-Fe-Ga-Co alloys will be also presented.展开更多
文摘Ferromagnetic shape memory alloys （FSMAs） such as NiMnGa, FePd and FePt are attractive as a new magnetic actuator material. They show a large magnetic-field-induced strain of 3% 9% due to the variant rearrangement. Recently, the present authors have reported that in the Ni-Ga-Fe alloy the martensitic transformationfrom the B2 and/or the L21 structures into a seven-layer or five-layer modulated structure occurs upon cooling. In this alloy system, however, it is impossible to obtain a martensite phase at RT with a Curie temperature （TC） higher than 100 ℃. In this work,the effects of substitution of Co for Ni on the martensitic and magnetic transformations,crystal structures and phase equilibria in Ni-Ga-Fe alloys were studied.Ni-Ga-Fe-Co alloys were prepared by induction melting under an argon atmosphere.Small pieces of specimens were taken from the ingot and homogenized at 1433 K for 24 h followed by quenching in water. The obtained specimens were aged at 773 K for 24 h and then quenched. The compositions of each phase were determined by energy dispersion X-ray spectroscopy （EDX）. The martensitic transformation temperatures and TC were measured by differential scanning calorimetry （DSC） and vibrating sample magnetometer （VSM） measurement. The crystal structure of martensite phase was observed by X-ray diffractmeter （XRD） and transmission electron microscope （TEM）.The Curie temperature TC was increased with increasing Co content while the martensitic transformation temperature slightly decreased. In the Ni<sup>54-x Ga<sup>27 Fe<sup>19 Cox ,TC increases from 303 K to 408 K with increasing Co content from x=0 to x=6. The crystal structure of the martensite phase and the phase equiribria in the Ni-Fe-Ga-Co alloys will be also presented.
