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第7期 隋延力等：Nd2.3feo.7NbB6纳米晶永磁合金的磁性能与微观结构 711. Microstructure and magnetic properties of an Nd12.3Fes0.7NbB6 nanocrystal perma- nent magnet SUI Yanli,CHEN Zhian2,BAO Xiaoqian,ZHANG Maoeai,ZHOU Shouzeng 1)State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing.Beijing 100083.China 2)Institute of Powder Metallurgy.University of Science and Technology Beijing.Beijing 100083.China ABSTRACI The microalloying effect of niobium on the microstructure and magnetic properties of an Nd2Fel4B nanocrystal permanent magnet was investigated.The results show that niobium addition promotes the formation of amorphous phase and stabilizes the amorphous phase.During the annealing,precipitate phase after niobium adding restrains the growth of grains,uniforms the size of grains,and enhances the magnetic properties of the alloy.The optimum magnetic properties ofJ=0.8998T,H-912.64kA'mand (BH)=126.24kJm3 were obtained by annealing a melt-spun Nd12.3Fe80.7 NbB6.0 amorphous ribbon at 550C for 10 min.But the magnetic properties decreased when the annealing temperature further increased. KEY WORDS Nd2Fe14B;magnetic properties;nanocrystals;amorphous phase (上接第693页) Spheroidized and ultra fine structure formed by cold rolling and annealing of eutec- toid pearlite steel FENG Zhiming,YANG Wangyue Materials Science and Engineering School,University of Science and Technology Beijing.100083 Beijing.China ABSTRACI The effect of cold rolling followed by annealing on the ultra refinement of microstructure and the mechanical properties of eutectoid steel was investigated.The experimental results showed that the combination of cold rolling to90and annealing within the temperature range of 600-700C leads a duplex microstructure consisting of sub micron ferritic grains and dispersive cementite particles.The distribution of cementite particle size displayed bimodal.In comparison with traditional spheroidizing treatment,the spheroidization time was sig- nificantly shortened and the microstructure markedly refined.This could be attributed to the formation of high- density dislocations and vacancies during cold deformation,which provided a high diffusion path of carbon atoms.The formation of dispersive distribution of fine cementite particles could be explained by the mechanism of dissolution re precipitation.It is also indicated that the present combined treatment of cold rolling and anneal- ing results in pronounced increases in yield strength and ultimate strength,a slight decrease in tensile plasticity, and a relatively high yield ratio. KEY WORDS eutectoid steel;cold-rolling:ultra fine grain;spheroidization:recrystallization annealingMicrostructure and magnetic properties of an Nd12∙3Fe80∙7NbB6 nanocrystal permanent magnet SUI Y anli 1）CHEN Zhian 2）BAO Xiaoqian 1）ZHA NG Maocai 1）ZHOU Shouzeng 1） 1） State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology BeijingBeijing100083China 2） Institute of Powder MetallurgyUniversity of Science and Technology BeijingBeijing100083China ABSTRACT The microalloying effect of niobium on the microstructure and magnetic properties of an Nd2Fe14B nanocrystal permanent magnet was investigated．The results show that niobium addition promotes the formation of amorphous phase and stabilizes the amorphous phase．During the annealingprecipitate phase after niobium adding restrains the growth of grainsuniforms the size of grainsand enhances the magnetic properties of the alloy．The optimum magnetic properties of Jr＝0∙8998THci＝912∙64kA·m －1and （BH）m＝126∙24kJ·m －3 were obtained by annealing a melt-spun Nd12∙3Fe80∙7NbB6∙0 amorphous ribbon at 550℃ for 10min．But the magnetic properties decreased when the annealing temperature further increased． KEY WORDS Nd2Fe14B；magnetic properties；nanocrystals；amorphous phase （上接第693页） Spheroidized and ultra-fine structure formed by cold-rolling and annealing of eutectoid pearlite steel FENG ZhimingY A NG Wangyue Materials Science and Engineering SchoolUniversity of Science and Technology Beijing100083BeijingChina ABSTRACT The effect of cold rolling followed by annealing on the ultra-refinement of microstructure and the mechanical properties of eutectoid steel was investigated．The experimental results showed that the combination of cold rolling to90％ and annealing within the temperature range of600－700℃ leads a duplex microstructure consisting of sub-micron ferritic grains and dispersive cementite particles．The distribution of cementite particle size displayed bimodal．In comparison with traditional spheroidizing treatmentthe spheroidization time was significantly shortened and the microstructure markedly refined．This could be attributed to the formation of highdensity dislocations and vacancies during cold deformationwhich provided a high diffusion path of carbon atoms．The formation of dispersive distribution of fine cementite particles could be explained by the mechanism of dissolution-re-precipitation．It is also indicated that the present combined treatment of cold rolling and annealing results in pronounced increases in yield strength and ultimate strengtha slight decrease in tensile plasticity and a relatively high yield ratio． KEY WORDS eutectoid steel；cold-rolling；ultra-fine grain；spheroidization；recrystallization annealing 第7期 隋延力等： Nd12∙3Fe80∙7NbB6 纳米晶永磁合金的磁性能与微观结构 ·711·