材料期刊网

Effect of Interfacial Bonding on the Toughening of Al_2O_3/Ni Ceramic Matrix Composites

Xudong SUN(Dept. of Materials Science and Engineering , Northeastern University , Shenyang 110006 , China)J.A. Yeomans(Dept. of Materials Science and Engineering , University of Surrey , Guildford , Surrey GU2 5XH , UK)

材料科学技术（英文）

The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.

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Hydrogen Reduction and Microstructural Changes of ISF Sinter

Yixin HUA (Dept. of Metallurgy , Kunming University of Science and Technology , Kunming 650093 , China)F.R.Sale (Manchester Materials Science Centre , University of Manchester and UMIST , Manchester M1 7HS , UK)

材料科学技术（英文）

The reduction rate and microstructural changes of imperial smelting furnace (ISF) sinter have been investigated by means of thermogravimetric analysis, X-ray difFraction (XRD), scanning electron microscope (SEM ), energy dispersive analysis of X-ray (EDAX) and optical microscope.It is demonstrated that the overall reaction rate of the reduction is influenced by temperature and hydrogen partial pressure in H2 /N2 gas mixtures. There are two distinct zones observed in the partially reduced sinter. The reduction of zincite proceeds predominantly in a narrow range between the two zones, while the reduction of tead oxide and silicate takes place throughout the sinter. The differences between zincite and lead oxide or silicate in reducibility are analysed by thermodynamlcs. The phase transformations and microstructural changes occurring during the reduction process are discussed

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PHYSICAL SIMULATION OF INTERFACIAL CONDITIONS IN HOT FORMING OF STEELS

Y. H. Li , M. Krzyzanowski , J. H. Beynon and C. M. Sellars IMMPETUS( Institute for Microstructural and Mechanical Process Engineering: The University of Sheffield , Sheffield SI 3JD , UK)

金属学报(英文版)

In the last few years,substantial experimental simulation and mumerical modelling hare been carried out in IMMPETUS to characterise the interfacial heat transfer and friction conditions during hot forging and rolling of steels. Emphasis has been placed on the influence of the oxide scale which forms on the steel workpiece. In the present paper, the experimental methods used for investigating interfacial heat transfer and friction conditions are described. Theses include hot flat rolling of steel slabs and hot axi- symmetric forging of steel cylinders and rings.Temperature measurements and computations demon- strate that for similar conditions, similar conditions, the effective interfacial heat transfer coefficients (IHTC) derived for hot rolling are significantly higher than those for forging, mainly due to the contribution of scale cracking during rolling. On the basis of experimental observations and numerical analysis,physical models for interfacial heat transfer in forging and rolling have been established. In addition, hot" sandwich" rolling and hot tensile tests with finite element modelling have been carried out to evaluate the hot ductility of the oxide scale.The results indicate that the defomation, cracking and decohesion behaviour of the oxide scale depend on deformation temperature, strain and relative strengths of the scale layer and scale - steel interface.Finaly, friction results from hot ring compression tests and from hot rolling with forward/backward slip measurements are reported.

关键词: interfacial heat transfer , null , null , null , null , null

Three Dimensional Simulation of Upset Forging by Using Variational Upper Bound Method

Jiang QIN(School of Mechanical Engineering , University of Bath , Claverton Down , Bath BA27AY , UK)

材料科学技术（英文）

The variation principle is discussed and Rayleigh-Ritz method is proposed for construction of veloci ty field. A kinematically admissible velocity field based on polynomials was appIied to the determina tion of forging load and deformed buIge profile during upset forging of blocks. Simulation of upsetforging of rectangular blocks under various friction condjtions was performed. Comparison of the computed results with experiments and FEM shows good agreement. It is shown that this techniquecan be used for 3D simulation of metal forming process.

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低碳低合金钢的静力韧度与断裂韧度

芦琳 , 李周波 , 毕宗岳 , 薛磊红 , 马璇

钢铁

采取静拉伸和平面应变断裂韧性测试方法,测量了S355,S275,Q345D,Q345E 4种低碳低合金钢自室温至-100℃的基本力学性能,包括屈服强度、抗拉强度、静力韧度、断裂韧度以及韧脆转变温度,试图寻找4种金属材料静力韧度和断裂韧度之间的关系;通过对200多组样品的试验结果进行分析,发现4种金属材料在其各自韧脆转变温度之上的静力韧度Uk和断裂韧度J02BL存在线性关系.

关键词: 静力韧度 , 断裂韧度 , 韧脆转变温度

英国钢铁工业铁矿石烧结过程中的二垩英的形成及抑制

钢铁

Corus UK已经研究出减少铁矿石烧结过程中二垩英形成和排放的技术.94次测量结果表明五个英国烧结厂主要废气烟囱的排放物浓度范围为0.28～4.4 ng I-TEQ/m3.总平均值为1.19 ng I-TEQ/m3,该数值略高于英国环境局为新工厂制定的可以达到的排放限-1 ng I-TEQ/m3.基础研究总结出二垩英极可能在火焰锋前的烧结床中形成.当尿素在料带前加入到烧结混合料中时,抑制试验取得了成功,二垩英排放量至少减少50%.加入尿素似乎可提供一种成本有效的二垩英抑制方法,该试验正继续进行以证实该技术的长期可行性.

关键词: 二垩英 , 铁矿石烧结 , 形成 , 抑制