材料期刊网

Wear-resisting Oxide Films for 900℃

M.B.Peterson(Wear Sciences Corporation , Arnold , Maryland , USA)Shizhuo LI(Institute of Metal Research , Chinese Academy of Sciences , Shenyang 110015 , China)S.F.Murray(Rensselaer Polytechnic Institute , Thoy , New York , USA)

材料科学技术（英文）

A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. Improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100℃ from 900℃. For unalloyed Ni friction and surface damage increases at 400℃ to 500℃. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni.Low friction at temperature above 500℃ and reasonable values (0.32~0.42) at low temperature are obtained.

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THE INFLUENCE OF ENVIRONMENT ON FATIGUE AND FRACTURE OF IRON ALUMINIDES

STOLOFF , N.S. and ALVEN , D.A.(Department of Materials Engineering Rensselaer Polytechnic Institute Troy , New York , 12180-3590 , USA)

金属学报(英文版)

This paper reviews recent research on embrittlement of iron aluminides brought about by exposure to moisture or hydrogen. The tensile and fatigue crack growth behavior of several Fe-Al alloys, ranging in aluminum content from 16 to 35a%, is described. It will be shown that tensile ductility and fatigue crack growth behavior are dependent on type and degree of long range order, grain structure, temperature and environment. Environments studied include vacuum,oxygen, hydrogen gas, electrolytically charged hydrogen and moist air. All cases of embrittlement are ultimately traceable to the interaction of hydrogen with the lattice.

关键词: : aluminides , null , null , null , null

A NEW MOLYBDENUM OXIDE PHASE

FANG Zheng ZHANG Pingmin CHEN Xinmin Central-South University of Technology , Changsha , China FANG Zheng , Associate Professor , Dept.of Chemistry , Central South University of Technology , Changsha 410083 , China

金属学报(英文版)

A new molybdenum oxide phase which exists in bomb combustion products of Mo was found. It has been determined that this phase is a transformed MoO_3 of triclinic system.One set of its lattice parameters was also determined from the X-ray diffraction data as α=0.4049± 0.0001 nm,b=0.5079±0.0003 nm,c=1.4339±0.0009 nm,α=115.16±0.08°,β=90.69± 0.14°,γ=105.58±0.05° and unit cell volume=0.2544 nm~3.

关键词: Mo oxide , null , null

A NEW MORPHOLOGY OF MARTENSITE

ZHONG Jiaxiang QI Yan Beijing Institute of Technology , Beijing , ChinaZHANG Xiumu GUO Yunyi Institute of Metal Research , Academia Sinica , Shenyang , China Beijing Institute of Technology , Beijing 100081 , China

金属学报(英文版)

A new “mid-relief” plate martensite was observed together with lenticular plate and thin plate martensites in Fe-29.37Ni-0.34C alloy after twice stepped cooling:-100/-120℃, -120/-140℃,-155/-165℃ and -165/-196℃,by means of colour metallography and TEM.The morphology of martensites changes with decreasing M_s temperature.The “mid-relief” plate martensite is characterized by the intensive mid-relie and the substructures of symmetric double twins or half twins and half dislocations,the formation of this martensite can be interpreted by a stress-induced co-generated mechanism.

关键词: martensite , null , null

A NEW KOSSEL ORIENTATION METHOD OF CRYSTAL

HUANG Rong WANG Guanying Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China HUANG Rong Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China

金属学报(英文版)

A new Kossel orientation method of crystal is developed.Only the distances among three in- tersections of the Kossel lines on the indexed Kossel patterns observed are necessary.for de- termining the orientation.Thus,the error may be eliminated and the orientation precision may be improved to be within 0.3°.

关键词: Kossel orientation method

A NEW METHOD FOR SYNTHESIZING NANOCRYSTALLINE ALLOYS

Journal of Applied Physics

A new method to prepare nanocrystalline alloys was developed by means of crystallization from amorphous alloys. By using this method, a Ni-P alloy with 9 nm crystallites was synthesized. The structure and grain sizes of the alloy were examined by means of x-ray diffraction, transmission electron microscopy, and high resolution electron microscopy. Specific heat capacity and thermal expansion coefficient of the nanocrystalline Ni-P alloy prepared by this method were found to be greater than those of the coarse-grained crystalline alloy by 12.3% and 56.2%, respectively. A new micromechanism for nanometer-sized crystallites formation is discussed.

关键词: sized crystalline materials

A NEW EVALUATION PROCEDURE FOR CRACK CLOSURE

International Journal of Fatigue

Bending fatigue tests can be used as a simple method for the determination of load-displacement curves near threshold for specimens containing surface cracks. The test method involves a strain gauge technique that yields highly reproducible results for cyclic loading from positive to negative stress ratios. Applying a new evaluation procedure one obtains DELTA-K(th,eff) values that are considered to be more realistic compared with those determined by conventional methods.

关键词: crack closure;bending tests;load-displacement curves;strain gauges;displacement gauge;fatigue;propagation

A new probe for the investigation of soil corrosivity

Corrosion

A new type of soil corrosivity probe was developed that could be used to measure not only corrosion current density (i(corr)) and corrosion potential (E-corr) of metals in soil, but also parameters of soil such as resistivity (rho), redox potential (Eh(7)), and temperature in a field corrosion test. The stable i(corr) of low-carbon steel (LCS) measured by the probe was in satisfactory agreement with the weight loss in practice. Results showed that the probe could provide a valuable tool for measuring soil corrosivity.

关键词: low-carbon steel;corrosivity;electrochemical impedance spectroscopy;electrochemical probe;soils

Mechanical properties of a new electrorheological fluid

Solid State Communications

We have extended the Rayleigh identity based on a multipole expansion theory to analyze the mechanical properties of a new type of electrorheological (ER) system that consists of a novel doubly coated particle in silicone oil. The function of the inner conducting layer of the particle has been investigated. From the shear strain (theta) dependence of effective dielectric constant, the dependence of static yield stress (tau(s)) and shear modulus (G) on the applied electric field are presented. Implications for the design of ER fluids are discussed briefly. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词: electrorheological fluids;effective dielectric constant;static yield;stress;shear modulus;conductivity;spheres;forces

A New Approach to Isothermal Precipitation Kinetics of Carbides

Wantang FU , Zheng WANG , Tianfu JING and Yangzeng ZHENG (Dept. of Materials Engineering , Yanshan University , Qinhuangdao 066004 , China)Jianguo MA(Harbin Frame Factory of Electrical Cable , Harbin , China)

材料科学技术（英文）

A new approach to isothermal precipitation kinetics of carbides in undercooled austenite has been proposed firstly, which is based on measuring the changes of Ms point vs holding time at a certain temperature. The isothermal precipitation kinetics (PTT) Curve of carbides was obtained by the use of the method for 13Cr-8Mn-0.07N stainless steel, and compared with the results of chemical phase analysis and TEM method. The results show that the new method is more sensitive and convenient than the other methods.

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