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RHEOLOGICAL BEHAVIOURS OF CAST STEEL DURING SOLIDIFICATION

LIN Jialiu ZHU Shigen YU Zhenzong Tsinghua University , Beijing , China

金属学报(英文版)

The stress-strain relation for cast low alloy carbon steel at solidification temperature has been examined by the authors' own desingned apparatus for rheological properties measurement.The rheology model,the stress-strain constitutive equation and the rheological parameters therefrom of the cast steel were proposed.Thus the theoretical basis and calcula- ting data for computerized s#nulation on the stress-strain relation and thermal cracking of the cast steel were suggested.

关键词: rheological behaviour , null , null , null , null

FRACTAL GEOMETRY STUDY OF CORRELATION BETWEEN IMPACT TOUGHNESS OF STEEL AND PARAMETERS OF FREE-CUTTING PHASE

JIANG Laizhu CUI Kun Huazhong University of Science and Technology , Wuhan , China

金属学报(英文版)

Studies were made of the calculation of fractal dimension of transverse impact fracture sur- face,and of the correlation between impact toughness of steel and parameters of free-cutting phase by means of the developed fractal geometry model of crack propagation.It is believed that the area fraction,f,of free-cutting phase is negligibly influential to the longitudinal im- pact toughness,as f1 .While the aspect ratio,saying ratio of length to width,of free-cut. ting phase is inversely influential to the transverse impact toughness.This may .be the reason why the transverse impact toughness of free-cutting steel containing more rare earth contrast to sulphur is even higher than the low sulphur containing steel.

关键词: fractal geometry , null , null

FRICTION MARTENSITE AND ITS TEMPERING CHARACTERISTICS

Liu Zhengyi Fu Jian Zhuang Yuzhi South China University of Technology , Guangzhou , China Correspondent:LIU Zhengyi professor , Dept.of Mechanical Engineering No.2 , South China University of Technology , Guangzhou , China

金属学报(英文版)

The nature of“white layer”found in 55SiMnMo steel subjected to friction test has been stu- died using TEM,SEM,X-ray diffraction and EPMA techniques.It is shown that the struc- ture of the“white laver”on the rubbing surface is duplex,consisting of a special martensite and some austenite.This layer may be 25—50 μm thick.It is ultrafine,with grain diametric approximately 30 nm.Its micro-hardness may be as high as Hm 1500 and is capable of cut- ting glass.It has superb corrosion resistance and resists tempering.Its mierostructure and hardness undergo changes only when the steel is tempered above 500℃.

关键词: friction , null , null

含Nb-Ti低碳微合金钢中纳米碳化物的相间析出行为

李小琳 , 王昭东

金属学报 doi:10.11900/0412.1961.2014.00582

采用热膨胀实验研究了等温温度对Nb-Ti微合金钢组织、性能及析出行为的影响规律,利用TEM对不同温度等温后试样的析出行为进行观察和分析.结果表明,不同温度等温后试样中均可观察到相间析出碳化物,且降低等温温度可显著细化相间析出碳化物所在面面间距、相间析出碳化物所在面内析出物间距及相间析出碳化物尺寸.具有层状分布特征的相间析出碳化物所在面呈现弯曲和平直2种形态,其中平直型相间析出碳化物所在面平行于铁素体的{011},{012},{013}和{035}面.经HRTEM确定相间析出碳化物具有NaC1型晶体结构,晶格常数为0.434 nm,且与铁素体基体符合Baker-Nut-ting(B-N)关系,经EDS分析确定相间析出碳化物为(Nb,Ti)C.利用Orowan机制对析出强化量进行估算,结果表明不同等温温度下析出强化量均大于300MPa.

关键词: Nb-Ti微合金钢 , 相间析出 , Vickers硬度 , 高分辨透射电子显微术 , 取向关系 , 错配度

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