Three types of NdFeB magnets with the same composition and different grain sizes were prepared,and then the grain boundary diffusion was conducted using metal Tb under the same technical parameters.The effect of grain...Three types of NdFeB magnets with the same composition and different grain sizes were prepared,and then the grain boundary diffusion was conducted using metal Tb under the same technical parameters.The effect of grain size on the grain boundary diffusion process and properties of sintered NdFeB magnets was investigated.The diffusion process was assessed using X-ray diffractometer,field emission scanning electron microscope,and electron probe microanalyzer.The magnetic properties of the magnet before and after diffusion were investigated.The results show that the grain refinement of the magnet leads to higher Tb utilization efficiency and results in higher coercivity at different temperatures.It can be attributed to the formation of a deeper and more complete core-shell structure,resulting in better magnetic isolation and higher anisotropy of the Nd_(2)Fe_(14)B grains.This work may shed light on developing high coercivity with low heavy rare earth elements through grain refinement.展开更多
采用光学显微镜（OM）、透射电镜（TEM）、抗拉强度和电导率测试等方法研究了不同温度时效后大型发电机转子用Cu-Ni-Si合金槽楔组织和性能变化规律。结果表明：合金在热挤压过程中发生动态回复与再结晶,热挤压后为再结晶组织,晶粒内部...采用光学显微镜（OM）、透射电镜（TEM）、抗拉强度和电导率测试等方法研究了不同温度时效后大型发电机转子用Cu-Ni-Si合金槽楔组织和性能变化规律。结果表明：合金在热挤压过程中发生动态回复与再结晶,热挤压后为再结晶组织,晶粒内部有贯穿整个晶粒的退火孪晶。在时效阶段屈服强度和抗拉强度随温度变化表现为先升高后下降的趋势,在430℃时过饱和固溶体发生有序化转变和第二相析出,基体上弥散分布的细小析出相和长程有序相会阻碍位错运动,提高力学性能。在550℃时效阶段合金处于过时效状态,析出相主要为Ni2Si,已经明显长大,对位错阻碍作用减弱,合金力学性能下降,但电导率始终保持上升的趋势。随时效温度升高,试样拉伸断口形貌逐渐由解理型转变为韧窝型,表明合金塑性逐渐提高。实验结果表明,在430℃时效3 h Cu-Ni-Si合金具有最佳的综合性能,屈服强度为650 MPa,抗拉强度为760 MPa,电导率为43.2%IACS。展开更多
基金Key Research and Development Program of Shandong Province(2021CXGC010310)Shandong Province Science and Technology Small and Medium Sized Enterprise Innovation Ability Enhancement Project(2023TSGC0287,2024TSGC0519)+1 种基金Shandong Provincial Natural Science Foundation(ZR2022ME222)National Natural Science Foundation of China(51702187)。
文摘Three types of NdFeB magnets with the same composition and different grain sizes were prepared,and then the grain boundary diffusion was conducted using metal Tb under the same technical parameters.The effect of grain size on the grain boundary diffusion process and properties of sintered NdFeB magnets was investigated.The diffusion process was assessed using X-ray diffractometer,field emission scanning electron microscope,and electron probe microanalyzer.The magnetic properties of the magnet before and after diffusion were investigated.The results show that the grain refinement of the magnet leads to higher Tb utilization efficiency and results in higher coercivity at different temperatures.It can be attributed to the formation of a deeper and more complete core-shell structure,resulting in better magnetic isolation and higher anisotropy of the Nd_(2)Fe_(14)B grains.This work may shed light on developing high coercivity with low heavy rare earth elements through grain refinement.
文摘采用光学显微镜（OM）、透射电镜（TEM）、抗拉强度和电导率测试等方法研究了不同温度时效后大型发电机转子用Cu-Ni-Si合金槽楔组织和性能变化规律。结果表明：合金在热挤压过程中发生动态回复与再结晶,热挤压后为再结晶组织,晶粒内部有贯穿整个晶粒的退火孪晶。在时效阶段屈服强度和抗拉强度随温度变化表现为先升高后下降的趋势,在430℃时过饱和固溶体发生有序化转变和第二相析出,基体上弥散分布的细小析出相和长程有序相会阻碍位错运动,提高力学性能。在550℃时效阶段合金处于过时效状态,析出相主要为Ni2Si,已经明显长大,对位错阻碍作用减弱,合金力学性能下降,但电导率始终保持上升的趋势。随时效温度升高,试样拉伸断口形貌逐渐由解理型转变为韧窝型,表明合金塑性逐渐提高。实验结果表明,在430℃时效3 h Cu-Ni-Si合金具有最佳的综合性能,屈服强度为650 MPa,抗拉强度为760 MPa,电导率为43.2%IACS。
