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相场方法模拟AZ31镁合金的静态再结晶过程

高英俊罗志荣胡项英黄创高

金属学报 doi:10.3724/SP.J.1037.2010.00272

为了获得合金静态再结晶前的变形晶粒组织, 应用网格畸变模型与相场模型结合, 生成变形合金再结晶前的初始晶粒组织; 针对合金不同变形区域的特征和体系储存能分布不均匀的特点, 分别引入反映不同变形区域的储存能分布的权重因子和变形区域的特征状态因子, 构造多状态的非均匀自由能密度函数. 在此基础上,应用相场动力学方程模拟了AZ31镁合金的静态再结晶过程的微结构演化,系统地分析了再结晶转变动力学曲线和Avrami曲线, 以及储存能释放规律和再结晶晶粒尺度分布. 模拟得到的动力学规律符合JMAK理论, 所得的Avrami曲线可近似看成一条直线, 对应于真应变ε=0.25, 0.50, 0.75和1.00,该直线的平均斜率分别为2.45, 2.35, 2.19和2.15. Avrami时间指数随变形量的增加而降低. 变形程度大的合金, 储存能释放的速度快, 完成静态再结晶所需的时间短.基于本文提出的模型, 结合相场方法计算模拟所得的结果与已有的理论结果和实验结果符合良好.

关键词: 相场模型 , static recrystallization , plastic deformation , microstructure , AZ31 Mg alloy

55SiMnMo钢断口微坑形成过程的研究

梁思祖 , 梁耀能 , 刘正义

金属学报

采用扫描电镜拉伸装置,对55SiMnMo钢正火组织进行拉断观察,发现其断口为微坑型延性断口。微坑形核于铁素体片内,其尖细的撕裂棱是由奥氏体经受强烈的范性变形而形成的。

关键词: 微坑 , plastic deformation , ductile fracture , steel 55SiMnMo

ZMl Mg合金的表面滚压强化

冯忠信 , 张建中 , 陈新增

金属学报

研究了表面滚压对ZM1Mg合金疲劳强度和疲劳缺口敏感度的影响。结果表明,滚压可使其光滑疲劳极限提高57%,缺口疲劳极限提高200%,大大降低疲劳缺口敏感度,使q出现负值。hcp的ZM1Mg合金滚压时以滑移和孪生方式变形和形变强化,引入高的残余压应力,有利于提高缺口疲劳极限和降低疲劳缺口敏感度,形变强化有助于发挥残余压应力的有利作用

关键词: 镁合金 , fatigue sensitivity , fatigue strength , plastic deformation , residual stress

固体范性形变与断裂的介观力学物理原理(英文)

V.E.Panin

金属学报

本文回顾了建立在物理介视力学基础上的固体范性形变与断裂的研究概况,从物理介现力学角度看,处于载荷下的固体是一个多层次的自治体系.依尺度不变原理,在微观、介观、宏观尺度上的范性流变,本质上是相互关联的.整体介观体积在介观尺度上按照“切变加旋转”的方式运动.固体范性形变与断裂可考虑为同样过程的二个阶段.

关键词: 介观力学 , plastic deformation , fracturel

5052铝合金板材热轧过程塑性变形及应力分布的三维热力耦合模拟

彭建 , 王永建 , 钟丽萍 , 孙勇 , 彭龙飞

材料热处理学报

对5052铝合金板材热轧过程进行了三维热力耦合模拟,综合考虑热轧过程中轧制速度、变形温度、道次压下量和摩擦系数等因素对热轧过程中轧件变形区内塑性变形和应力分布的影响,建立了多参数的热力耦合热轧模型.结果表明,在轧件变形区内,因加工硬化与动态软化的综合作用,其流变应力呈典型的动态再结晶特征.在变形区内轧件表面因金属流动剧烈,其等效塑性应变和应变速率远远大于轧件心部,塑性变形显著.轧制速度是轧件温度场分布最重要的影响因素之一,轧制速度越大,轧件的温升就越高;而温度是影响等效应力大小的主要因素,温度升高和应变速率降低都使得流变应力降低.

关键词: 5052铝合金 , 热轧 , 热力耦合 , 塑性变形 , 应力场

INVESTIGATION OF THE EFFECT OF TEMPERATURES ON TENSILE LOAD DROPS OF TITANIUM ALLOY

Z Zhang , ZH Tu , L.F. Li , L.Z. Zhaoand D. Jin (Cryogenic Laboratory Chinese Acaderw of Sciences , Beijing 100080 , China )H.J Lu (Beijing Institute of Aerospace Materials and Technology , Beijing 100076 , China)

金属学报(英文版)

Low temperature may greatly affect the mechanical properties of materials. Some in-teresting mechanical phenomena were detected at very low temperature. In this study,a multi-sample tensile installation was designed to study the plastic deformation be-havior for Ti-5Al-2.5Sn extra-low-interstitial (ELI) alloy at liquid helium temperature.The special geometrical instability phenomena in low temperature, serrated deforma-tion and multi necking, was studied in detail in this project. Slip and twinning were determined in the process of plastic fiow by SEM/TEM analysis. Efficts of temper-ature and sequential straining on load drops in tensile stress-strain curves were also studied. Optical measurement method was used to gauge the geometrical characteristic of multi-necking specimens. The sensitivity of partial thermoplastic deformation and the equivalency of low tempemture with high velocity of this material were studied by using micro-mechanics analysis.The criterion of geometrical instability has been discussed. A computer simulation of the low temperature instability of plastic fiow in Ti-5Al-2.5Sn ELI alloy has been carried out. A computer model has been established which links the hot dtffusion and the plastic fiow of hcp alloys under assumption that the tempemture is homogeneous within the specimen and that the heat exchange with the thermal bath is the control-ling step in the heat release. The computer simulation of the deformation curves as a function of several mechanincal, geometrical and thermal parameters provides a re-alistic description of the experiments. The experimental data available are discnssed in the light of the computer simulation model.

关键词: mechanical property , null , null

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