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MECHANICAL BEHAVIOUR OF GRAPHITE AND ITS ADJACENT ZONE TO MATRIX INTERFACE IN CAST IRON

HE Zerong JI Song LIN Guoxiong Fuzhou University , Fuzhou , China professor , Department of Mechanical Engineering , Fuzhou University , Fuzhou , 350002 , China

金属学报(英文版)

The micro-processes on tensile deformation and fracture of graphite-matrix interface in cast iron with ferrite matrix under SEM have been observed in situ.It was revealed that the graphite in cast iron would not be regarded as a cavity and not formed yet notch stress concentration.A new explanation on the effect of graphite on strength of cast iron was suggested.

关键词: cast iron , null , null

EFFECT OF DYNAMIC STRAIN AGING ON PURE BENDING FATIGUE STRENGTH OF AUSTENITIC STAINLESS STEEL

CHEN Wenzhe QIAN Kuangwu FuZhou University , Fuzhou , Fujian , China Lecturer , Dept.of Mechanical Engineering , Fuzhou University , Fuzhou , Fujian , China

金属学报(英文版)

The effect of various dynamic strain aging(DSA)pre-treatment processes on pure bending fatigue strength of an 18-8 austenitic stainless steel was investigated.The results show that DSA pre-treatment processes increase remarkably the fatigue strength and the strengthening effects increase with increasing pre-strain temperature and pre-strain.The fatigue limit of specimens pre-treated by DSA is 87% higher than that by solution treatment,and 20% high- er than that by cold-working.TEM observations show that the uniform and stable dislocation networks with high density formed after DSA pre-treatment,which suppress effectively the initiation and propugation of fatigue cracks and increase the fatigue strength of materials.

关键词: dynamic strain aging(DSA) , null , null

GRAIN SIZE AND ACTIVATION ENERGY OF SERRATED YIELDING

XIAO Lingang QIAN Kuangwu Fuzhou University , Fuzhou , Fujian , China Correspondent:QIAN Kuangwu Professor , Institute for Materials Research , Fuzhou University Fuzhou , Fujian 350002 , China

金属学报(英文版)

The apparent activation energy of serrated yielding was measured by two different methods for a commercial brass H68.The results showed that the apparent activation energy of serrat- ed yielding measured by a method involving(m+β)values increases with the grain size.In contrast,those measured by another method without involving(m+β)values are all the same for specimens with different grain sizes.Combining with the observation of the microstructures,the above phenomena have been explained.The method to measure the true activation energy of serrated yielding has also been proposed.

关键词: serrated yielding , null , null , null

EFFECT OF DYNAMIC STRAIN AGING ON LOW CYCLE FATIGUE BEHAVIOUR OF 18-8 AUSTENITIC STAINLESS STEEL

PENG Kaiping CHEN Wenzhe OIAN Kuangwu Fuzhou University , Fuzhou , China teaching assistant , Department of Mechanical Engineering , Fuzhou University , Fuzhou 350002 , China

金属学报(英文版)

Studies were made of the symmetric tensile-compressive low cycle fatigue behaviour and the influence of dynamic strain aging(DSA)pre-treatment of 18-8 austenitic stainless steel. Within the testing amplitude range of strain.±0.5 % to±1.5 %,the three processes of cyclic hardening,cyclic saturation and cyclic softening were observed.In the same amplitude of strain,the peak stress of the samples pre-treated by DSA is higher than that of solid-solu- tion and cold working pre-treatment,but no remarkable differences of the fatigue lives of them were found.TEM observation shows that the uniform and stable dislocation networks with high density form after DSA pre-treatment,which increases the cyclic peak stress.The cyclic softening results from the low dislocation density and elongated cell structure with low energy.

关键词: 18-8 austenitic stainless steel , null , null

FEATURE OF SERRATED YIELDING IN HIGH STRENGTH Al-Zn-Mg-Cu ALLOY

QIAN Kuangwu LI Xiaoqi ZHANG Haoguo Fuzhou University , Fuzhou , Fuiian , China

金属学报(英文版)

The temperature dependence of critical strain for serrated yielding in high strength A1-Zn-Mg-Cu alloy may be divided into two temperature regions.Their temperature coefficients of critical strain will be negative and positive,respectively.

关键词: serrated yielding , null , null , null

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