材料期刊网

Biaxiality Dependence of the Fracture Toughness for Glass in Plane Stress State

Yiwang BAO(China Building Materials Academy , Beijing 100024 , China)R. W Steinbrech (IWE1 , Juelich Research Center , Germany)

材料科学技术（英文）

The fracture behaviour of glass in biaxial stress state has been investigated. Fracture toughness of disk specimen with a straight-through crack was measured under biaxial tension and uniaxial tension loads respectively. The difference between them and the reasons for the difference are discussed. The influence of the stress parallel to crack on fracture of brittle material was demonstrated in theory and experiments. The results show that plane stress fracture toughness of glass is not a material constant. and that the fracture toughness measured in biaxial tension state is higher than that measured under uniaxial tension. The conventional fracture criterion upon the stress intensity factor is questioned in the case of biaxial stress problem, and the strain dependence of crack growth is discussed.

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R. erythropolis对赤铁矿和石英的吸附?捕收作用

杨慧芬 , 唐琼瑶 , 王传龙 , 张露 , 李甜

中国有色金属学报

为考察红城红球菌(Rhodococcus erythropolis,R. erythropolis)作为赤铁矿捕收剂使用的可能性及效果,对R. erythropolis形貌、细胞壁成分及其吸附前后赤铁矿、石英表面电性、疏水性进行分析,对赤铁矿、石英单矿物以及赤铁矿与石英矿1:1(质量比)混合矿进行浮选实验,对其在赤铁矿表面的吸附状况及吸附机理进行研究.结果表明,杆状R. erythropolis表面既含有非极性基团,又含有极性基团,使得其表面具有较高的负电性和较强的疏水性,因而对赤铁矿的吸附作用明显大于对石英的吸附作用.当以此细菌为捕收剂、在溶液 pH 值为6、R. erythropolis用量为75 mg/L时,赤铁矿的回收率为89.68%,而石英的回收率仅为26.25%.混合矿经过一次浮选,可获得铁品位和回收率分别为50.08%和76.41%的铁精矿.R. erythropolis在赤铁矿表面发生复杂的化学吸附且使赤铁矿颗粒形成疏水絮团,从而证实R. erythropolis可作为赤铁矿的捕收剂使用.

关键词: R. erythropolis , 微生物 , 赤铁矿 , 石英 , 吸附 , 絮团 , 捕收剂

R&D STATUS ON INTERMETALLICS IN CHINA

CHEN Guoliang(State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 , China)SHI Changxu (Academia Sinica , Beijing 100864 , China)

金属学报(英文版)

This paper briefiy introduces the R&D of intermetallics in China. R&D on intermetallics in a national scale in China began near ten years ago. The investigation in past years focused on the fundamental research and materials development. A significant progress has been made. Various components that made of Ti3Al Ni3Al, TiAl and Fe3Al have been successfully manufactured Some of them have been evaluted. It is expected that some intermetallic alloys will be produced in an industrial scale in the near future.

关键词: :intermetallic alloys , null , null , null

Key R&D activities for development of new types of wrought magnesium alloys in China

Transactions of Nonferrous Metals Society of China

Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies. The research activities are funded primarily through four government-supported programs: the Key Technologies R&D Program of China, the National Basic Research Program of China, the National High-tech R&D Program of China, and the National Natural Science Foundation of China. The key R&D activities for the development of new wrought magnesium alloys in China are reviewed, and typical properties of some new alloys are summarized. More attentions are paid to high-strength wrought magnesium alloys and high-plasticity wrought magnesium alloys. Some novel plastic processing technologies, emerging in recent years, which aim to control deformation texture and to improve plasticity and formability especially at room temperature, are also introduced.

关键词: wrought magnesium alloy;microstructure;properties;alloy designing;plastic deformation;research projects;y-zr alloys;mechanical-properties;mg-4y-4sm-0.5zr alloy;grain-refinement;rare-earth;microstructure;gd;phase;temperature;evolution

Structure and magnetic phase transition in R(Co1-xGax)(2) (R = Nd, Gd, Tb, Dy) compounds

Physica B-Condensed Matter

X-ray powder diffraction and magnetization measurements reveal that light rare earth and heavy rare earth have different effects on the structure, Curie temperature and magnetic phase transition of the compounds R(Co1-xGax)(2) (R = Nd, Gd, Tb, Dy) (x = 0.0-0.3). The lattice constant exhibits a giant increase with increasing Ga concentration in all compounds. The Curie temperature shows no variation for R = Nd, a monotonic decrease for R = Gd and a maximum for R=Tb and Dy, respectively. The Curie temperature is strongly related with volume expansion, in which a critical value of a(c) approximate to 7.26 Angstrom is reached. The observed magnetic transition in all compounds is well explained within the framework of the Inoue-Shimizu model. It is revealed that both the lattice constant and the Curie temperature have a strong relationship with the order of the magnetic phase transition. (C) 2003 Elsevier B.V. All rights reserved.

关键词: structure;Curie temperature;magnetic phase transition;itinerant-electron metamagnetism;intermetallic compounds;ac;susceptibility;order;temperature;behavior;r(co;yco2

Structure and magnetoelasticity of R(Zn1-xFex) (R = Tb, Dy) polycrystalline alloys

Ieee Transactions on Magnetics

The structure, magnetization, and magnetostriction of R(Zn1-xFex)(R = Tb, Dy) polycrystalline alloys were investigated by X-ray diffraction, vibrating sample magnetometry, and standard strain gauge techniques. It was found that TbZn1-xFex consists of a single Tb(Zn,Fe) phase with the cubic CsCl-type structure when x <= 0.2. DyZn1-xFex was found to consist of nearly a single Dy(Zn,Fe) phase in the range 0 <= x <= 0.15. A second Dy-rich phase appears when x > 0.15. The Curie temperature of the RZn1-xFex alloys increases with increasing Fe content when x <= 0.2. When Fe is substituted for Zn in RZn compounds, the magnetization increases with increasing Fe content. The magnetostriction of Tb(Zn1-xFex) alloys increases with increasing Fe content when x <= 0.1, and that of Dy(Zn1-xFex) alloys increases in the composition range 0 <= x <= 0.05.

关键词: magnetization;magnetostriction;rare earth-Zn compounds;structure;piezomagnetic properties;77 k;magnetostriction

MAGNETOCRYSTALLINE ANISOTROPY IN R2FE14-XCOXB1-YCY COMPOUNDS (R = ND, PR)

Journal of Magnetism and Magnetic Materials

The temperature dependence of the magnetocrystalline anisotropy field (mu-0H(a)) of R2Fe14B(1-y)C(y) and Nd2Fe12Co2B(1-y)C(y) (R = Nd, Pr; y = 0, 0.5) compounds has been determined by applying the SPD (singular point detection) technique in a high pulse magnetometer in the temperature range of 300-600 K. To determine the Curie temperature (T(c)) of the compounds, the ac initial susceptibility measurement was employed. It was found that the influences of carbon substituting for boron and cobalt substituting for iron on the Curie temperature are independent of each other and the latter has been understood as the case where all 2p electrons which transferred from carbon to 3d bands localize around Fe. The effect of crystal electric field acting on the rare earth site is dominant at temperatures below 400 K in R2Fe14B (R = Nd, Pr) compounds. The substitution of small amounts of cobalt for Fe does not affect the crystal electric field acting on the rare earth site very much.

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MAGNETIC-ANISOTROPY OF R2CO14B1-XCX COMPOUNDS (R=PR, ND)

Journal of Alloys and Compounds

High field magnetization curves have been measured at 4.2 K on magnetically aligned R2Co14B1-xCx (R = Pr, Nd; x = 0.0, 0.2 and 0.5) samples with the magnetic field applied parallel and perpendicular to the alignment direction. It is found that, for both the praseodymium and the neodymium compounds, the saturation magnetization decreases on substitution of carbon for boron. In the Nd2Co14B1-xCx system, the critical field of the first-order magnetization process (FOMP) increases with increasing carbon content. No FOMP is observed in the Pr2Co14B1-xCx system. The temperature dependence of the a.c. susceptibility shows that in Nd2Co14B1-xCx the spin reorientation temperature decreases with increasing carbon content. A spin reorientation phenomenon is also observed in Pr2Co14B0.8C0.2 and in Pr2Co14B0.5C0.5. Also in these compounds, the spin reorientation temperature decreases with increasing carbon content.

关键词: nd2fe14b;exchange;r2fe14b;field

METASTABLE R-PHASE IN Fe-Cr-Mo AND Fe-Cr-W ALLOYS

LIU Shicheng Dalian Railway Institute , Dalian , ChinaHAMAGOCHI Yoshikazu KUWANO Hisashi Muroran Institute of Technology , Muroran , Japan

金属学报(英文版)

The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transformed into stable μ-phase,Laves-phase,X-phase or σ-phase in the later stages.The crystallographic structure of metastable R-phase is rhombohedral with lattice parameters of a=0.9075 nm and α=74.45°.The chemical compo- sition of R-phase is Fe-(27.5—34.9)Mo-(0—25.5)Cr and Fe-(28.9—33.0)W-(9.36— 21.0)Cr in at.-% in Fe-Cr-Mo and Fe-Cr-W system,respectively.

关键词: Fe-Cr-Mo alloy , null , null , null

Fe-Cr-Mo,Fe-Cr-W合金中的过渡R相

刘世程 , 浜口由和 , 桑野寿

金属学报

研究了Fe-Cr-Mo、Fe-Cr-W合金的时效析出过程,发现在时效初期、两合金系中均有过渡R相析出,过渡R相为菱形点阵,α=0.9075nm,α=74.45°,其成分在Fe-Cr-Mo合金中为Pe-(27.5—34.9)Mo-(0—25.5)Cr,在Fe-Cr-W合金中为Fe-(28.9—33.0)W-(9.36—21.0)Cr(at.-％),时效后期,过渡R相分别向平衡相μ相、Laves相、χ相及σ相转变。

关键词: Fe-Cr-Mo合金 , Fe-Cr-W alloy , precipitation