材料期刊网

Interaction of Mechanical and Electrochemical Factors during Corrosion Fatigue of Fe-26Cr-1Mo Stainless Steel in 1M H_2SO_4 Solution

Jianqiu WANG , Jin LI , Ziyong ZHU and Wei KE (Corrosion Science Laboratory , Institute of Corrosion and Protection of Metals Chinese Academy of Sciences , Shenyang , 110015 , China)Qishan ZANG and Zhongguang WANG (State Key Laboratory for Fatigue and Fracture

材料科学技术（英文）

The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate, the characteristics of current response was mainly relative tp the process of new surface repassivation.The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate

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Laboratory of Fatigue and Fracture for Materials(LFFM)

WA NG Zhongguang Professor , Director of the LFFM , Shenyang , 110015 , China.

材料科学技术（英文）

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The Morphology of Rolling Contact Fatigue Fracture of Hardened Steels

WANG Xu , ZHANG Shouhua , CUI Peiyong Beijing University of Science and Technology , Beijing , China. Central Iron and Steel Research Institute , Beijing , China.

材料科学技术（英文）

Rolling Contact Fatigue(RCF) is a cumulative damage phenomenon when metals are subjected to repeated contact stresses. The fomation of pitting on the contact surface is the result of the rolling contact fatigue. The morphologies of rolling contact fatigue fracture of the har- dened steels (86CrHoV7, 42CrMo) show that strong resemblance in fractuye mechanisms exists between rolling contact fatigue and uni-axial fatigue. Since fatigue striations are hardly observed in hardened steels under uni-axial fatigue, it is interesting to note that the state of stress in rolling contact fatigue is more favor- able to ductile fractures than in uni-axial fatigue.

关键词: rolling contact , null , null , null , null , null

MECHANISM MAP OF TORSIONAL FATIGUE FRACTURE

HU Zhizhong WU Yusheng CAI Heping MA Lihua Xi′an jiaotong University , Xi′an , China Senior Engineer , Res.Inst.for Strength of Metals , Xi′an jiaotong University , Xi′an 710049 , China

金属学报(英文版)

Studies have been made of the torsional fatigue fracture life of notched specimens,the macroscopic fractography and microscopic fracture mechanism of steel 40Cr after various tempering treatments under different stresses,With the increase of stress,the fracture model changes from normal stress fracture to longitudinal shear one,and then transversal shear one. Under same stress,with the increase of strength,the fracture mode transfers from shear to normal stress fracture.The mechanism of normal stress fracture may be:transgranular frac- ture→striation+intergranular fracture→dimple+intergranular fracture,and of shear fracture may be:transgranular fracture→shear trace→dimple.Based on the experimental results,a fracture mechanism map of torsional fatigue has been drawn up.

关键词: mechanism map , 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

INFLUENCE OF TEMPERATURE ON FATIGUE CREEP INTERACTION FRACTURE MAP

ZHANG Hongxue XU Zhichao CHEN Guoliang University of Science and Technology Beijing , Beijing , China Professor , Faculty of Superalloy , University of Science and Technology Beijing , Beijing , China

金属学报(英文版)

The relative ratio of fatigue resistance to creep resistance of materials varies with test temper- ature.As the temperature decreases,the creep resistance,since it is a thermal activation pro- cess,becomes relatively larger than fatigue resistance.Therefore the fatigue damage becomes predominant,and results in expansion of fatigue fracture region(region F),and shrinkage even complete elimination of creep fracture region(region C).A materials parameter Ω can be defined to estimate the temperature at which the creep fracture region is completely de- pressed.This phenomenon could be understood on the basis of the integrated model of compet- itive and cumulative models of fatigue creep interaction.

关键词: creep fracture , null , null , null

Fatigue and fracture behavior of bulk metallic glass

Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science

Tensile, compressive, cyclic tension-tension, and cyclic compression-compression tests at room temperature were systematically applied to a Zr52.5CU17.9Al10Ni14.6Ti5 bulk metallic glass for comprehensive understanding of its damage and fracture mechanisms. Under tensile loading, the metallic glass only displays elastic deformation followed by brittle shear fracture. Under compressive loading, after elastic deformadon, obvious plasticity (0.5 to 0.8 pct) can be observed before the final shear fracture. The fracture strength under compression is slightly higher than that under tension. The shear fracture under compression and tension does not occur along the maximum shear stress plane. This indicates that the fracture behavior of the metallic glass does not follow the Tresca criterion. The fracture surfaces show remarkably different features, i.e., a uniform vein structure (compressive fracture) and round cores coexisting with the radiating veins (tensile fracture). Under cyclic tension-tension loading, fatigue cracks are first initiated along localized shear bands on the specimen surface, then propagated along a plane basically perpendicular to the stress axis. A surface damage layer exists under cyclic compression-compression loading. However, the final failure also exhibits a pure shear fracture feature as under uniaxial compression. The cyclic compression-compression fatigue life of the metallic glass is about a factor of 10 higher than the cyclic tension-tension fatigue life at the same stress ratio. Based on these results, the damage and fracture mechanisms of the metallic glass induced by uniaxial and cyclic loading are elucidated.

关键词: mechanical-properties;crack-propagation;zr-ti;enhanced plasticity;amorphous-alloys;high-strength;hydrostatic-pressure;matrix;composites;flow;deformation

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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Fatigue-Creep Interaction Fracture Maps and Life Prediction under Combined Fatigue-Creep Stress Cycling

CHEN Guoliang University of Science and Technology Beijing , Beijing , 100083 , China.

材料科学技术（英文）

The purpose of this paper is to introduce sys- tematically the theory of fatigue-creep interaction fracture map and its application.

关键词: fatigue-creep interaction fracture map , null

A QUANTITATIVE INVESTIGATION OF FATIGUE FRACTURE SURFACES BY USING THE FOURIER-TRANSFORM METHOD

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

In the present paper, the Fourier transform method (FTM) was applied in a study of fatigue fracture surfaces of commercial aluminum in order to relate the geometrical parameters on the fracture surface to the microstructure of the material. The results indicate that the power spectrum and the wave number are inversely related. An exponent n was indexed by curve fitting the power spectrum peaks of the fracture profile and was shown to correlate with the crack propagation rate da/dN, and da/dN can be inferred approximately from the correlation function.

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