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PREPARATION OF HIGH COERCIVE Sm-Fe-N PERMANENT MAGNET

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Acta Metallurgica Sinica(English Letters) 1993年第11期6卷 341-344页

作者： LIU Wei WANG Qun ZHAO Xinguo ZHAO Tong ZHANG Zhidong SUN Xiaokai Institute of Metal Research,Academia Sinica,Shengyang,China research assistant,Institute of Metal Research,Academia Sinica,Shenyang 110015,China

Using pure Sm and Fe powders as starting materials,high coercive Sm-Fe-N mag- nets have been prepared by mechanical alloying in combination with beat treatment and nitriding.The best result is:_iH_c=33.1 kA/cm(41.6 kOe)and(BH)_(max)=98.7 kJ/cm^3(12.4 MGOe).The phases formed in the specimens during mechanical alloying, crystallizing and nitriding processes were examined by X-ray diffraction technique.The magnetic properties of the specimens were measured with the pulsed magnetometer in field up to 12 T.Experimental results show that mechanical alloying is an efficient ap- proach for preparing high coercive magnets.As an important factor for obtaining a high coercivity,the grain sizes of magnets are about tens of nanometer.The presence of some soft magnetic phases in the specimens leads to a neck on the demagnetization curve.

关键词： Sm-Fe-N magnet mechanical alloying nitriding annealing

Oxidation of two-phase Cu-Cr alloys with different microstructures

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中国有色金属学会会刊：英文版 2001年第3期11卷 333-336页

作者：付广艳牛焱吴维 管恒荣沈阳化工学院机械工程系金属腐蚀与防护国家重点实验室辽宁沈阳 110021 中科院金属所金属腐蚀与防护国家重点实验室辽宁沈阳 110016

The oxidation of PM Cu 50Cr, MA Cu 40Cr and MS Cu 40Cr alloys at 800 ℃ in 0.1 MPa O 2 was studied. The most important difference of their oxidation behaviors is the formation of an exclusive chromia scale on the surface of the MS Cu 40Cr alloy and a continuous chromia layer beneath an outer CuO layer corresponding MA Cu 40Cr alloy, while a complex scale composing of CuO, Cu 2O, Cu 2Cr 2O 4 and Cr 2O 3 formed on the PM Cu 50Cr alloy. This result implies that alloy microstructure affects their oxidation behaviors largely. Microcrystalline structure provides numerous diffusion paths for reactive component chromium, shorter diffusion distance and rapid dissolution of Cr riched second phase. All these favor the exclusive formation of the most stable oxide. [

关键词： oxidation Cu Cr alloys powder metallurgy mechanical alloying sputtering

Microstructure and thermal stability of mechanically alloyed Al_3Ti/Al alloy

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中国有色金属学会会刊：英文版 2001年第2期11卷 266-269页

作者：林建国魏浩岩黄正 Department of Physics Xiangtan University Department of Materials Science and Engineering Beijing University of Aeronautics and Astronautics

The microstructure stability of Al 3Ti/Al alloy prepared by mechanical alloying (MA) was investigated in the simulating environment in which they may be used. The results show that the MA alloy possesses fine microstructure (the grain size is about 0.5 μm). After cycling loaded followed by heat exposure at 350 ℃ for 24 h, no microstructure coarsening of the alloy occurred, which means that the Al 3Ti/Al alloy behaves good microstructure stability at high temperature. The compression yield strength of the alloy reaches up to 247 MPa at 350 ℃. [

关键词： mechanical alloying Al 3Ti/Al alloy microstructure stability thermal stability

Phase Transformation in the Ball Milled Fe_(31)Co_(31)Nb_(8)B_(30) Powders

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Advances in Materials Physics and Chemistry 2013年第1期3卷 90-100页

作者： S.Azzaza S.Alleg J.J.Sunol Laboratoire de Magnetisme et Spectroscopie des Solides(LM2S) Departement de PhysiqueFaculte des SciencesUniversite Badji MokhtarAnnabaAlgerie Department de Fisica Universitat de GironaGironaSpain

The mechanical alloying process has been used to prepare nanostructured Fe31Co31Nb8B30 (wt%) alloy from pure elemental powders in a high energy planetary ball-mill Retsch PM400. Microstructural changes, phase transformation and kinetics were studied by X-ray diffraction, differential scanning calorimetry and M?ssbauer spectrometry. The crystallite size reduction down the nanometer scale (~8 nm) is accompanied by the introduction of internal strains up to 1.8% (root-mean square strain, rms). Further milling time leads to the formation of partially paramagnetic amorphous structure in which bcc FeCo nanograins are embedded. The kinetics of amorphization during the milling process can be described by two regimes characterized by different values of the Avrami parameter n1 = 1.41 and n2 = 0.34. The excess enthalpy due to the high density of defects is released at temperatures below 300°C. The glass transition temperature increases with increasing milling time.

关键词： Nanomaterials mechanical alloying X-Ray Diffraction Fe-Co-Nb-B System Amorphization Kinetics

Curie Temperature of the Intergranular Amorphous Phase in Nanocrystalline Fe_(89)Zr_7B_4 Alloy

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Advances in Manufacturing 1999年第4期3卷 318-320页

作者： XU Hui HE Kai-yuan HE Shu-li CHENG Li-zhi DONG Yuan-da XIAO Xue-shan School of Material Science&Engineering Shanghai University Northeastern University Zhengzhou University

The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe 89 Zr 7B 4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powders for 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than that of the intergranular phase with the same chemical composition in the nanocrystalline Fe 89 Zr 7B 4 alloy. The possible mechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α Fe grains.

关键词： mechanical alloying intergranular amorphous phase Curie temperature exchange coupling

Dependence of Nanocrystalline Phase Formation and Magnetic Properties in Fe_(25)Ni_(75) on Ball Milling Time

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Advances in Manufacturing 1998年第4期 43-46页

作者： Xu Shiyue Chen Hangde He Zhengming Shi Yaoming Dong Chuanhua Zhang Zhengming (College of Sciences)

Nanocrystalline Fe 25 Ni 75 powders were prepared by the mechanical alloying process . They were investigated by X ray diffraction and magnetic measurements .The ball milling time dependence of grain size, internal strain and magnetic properties has been discussed. The results show that the formation of Fe 25 Ni 75 alloy phase is almost completed after milling for 30 hours. The reduction of grain size accompanied by the growth of internal strain was observed after extended milling. An average grain size about 10-20 nm of alloyed powders has been determined by Sherrer formula estimation. The saturation magnetisation Ms has a slight increase when the average grain size continues to decrease by intensive milling. This fine size of mechanically alloyed powders (10-20 nm) results in a single domain magnetic structure and the formation of superparamagnetic phase.

关键词： mechanical alloying coercivity saturation magnetisation internal strain

Magnetic Anisotropy of mechanically Alloyed Fe_(25) Ni_(75) Nanocrystallites

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Advances in Manufacturing 2000年第1期4卷 60-63页

作者： Shi-yue Xu Zheng-ming He Yao-ming Shi Zheng-ming Zhang Chuan-hua Dong Hang-de Chen College of Sciences Shanghai University Shanghai 200436 China

The magnetic anisotropy of Fe 25 Ni 75 nanocrystallites in the range of 10～20 nm was measured by the law of approach to saturation. The samples were prepared by mechanical alloying process, and the average crystal size was determined by X ray diffraction. The effective magnetic anisotropy of these fine particles is found in an order of 10 6 erg/cm 3 that is much greater than that of normal crystal size of particles. The dependence of magnetic anisotropy on the particle size was studied. It has been demonstrated that the strain anisotropy occupies the most of the total magnetic anisotropy, and the internal strain is a critical factor for their magnetic properties.

关键词： magnetic anisotropy saturation magnetization strain anisotropy ultra fine particles single domain mechanical alloying

Effects of Consolidation Process on the Microstructure and mechanical Properties of ODS Ferritic Alloy

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Effects of Consolidation Process on the Microstructure and M...