AZ91D变形镁合金的动态应变时效现象

镁合金

第20卷第8期 Vol.20 No.8 中国有色金属学报 2010年8月 The Chinese Journal of Nonferrous Metals Aug. 2010

文章编号:1004-0609(2010)08-1455-06

AZ91D变形镁合金的动态应变时效现象

林 娜1,曾绍峰1, 2,彭开萍1,陈文哲1, 2

(1. 福州大学 材料科学与工程学院,福州 350108; 2. 福建工程学院 材料科学与工程系,福州 350108)

摘 要:在应变速率为1.11×10 4~1.67×10 3 s 1、温度为248~523 K的条件下,对固溶态AZ91D变形镁合金进行拉伸试验。结果表明: 在一定的拉伸应变速率和温度区间拉伸时,AZ91D镁合金在形变过程中发生动态应变时效(DSA)现象,其典型特征表现为其拉伸曲线出现锯齿波,所对应的锯齿波类型分别呈A型及A+B混合型;应变速率敏感性系数为负值;且出现加工硬化速率峰值;出现锯齿屈服的临界应变量随变形温度升高而减小,而随应变速率增加而增大;当形变温度大于323 K时,加工硬化速率随着温度升高反而急剧增大,在368 K时达到峰值。 关键词:AZ91D变形镁合金;动态应变时效;锯齿屈服;负应变速率敏感系数;加工硬化速率 中图分类号:TG113 文献标志码:A

Dynamic strain aging phenomenon of

AZ91D wrought magnesium alloys

LIN Na1, ZENG Shao-feng1, 2, PENG Kai-ping1, CHEN Wen-zhe1, 2

(1. College of Materials Science and Engineering, Fuzhou University,Fuzhou 350108, China;

2. Department of Materials Science and Engineering, Fujian University of Technology, Fuzhou 350108 China)

Abstract: A series of tensile tests of as-solid-solution treated AZ91D wrought magnesium alloys were carried out at strain rates ranging in 1.11×10 4 1.67×10 3 s 1 and temperatures ranging in 248 523 K. The results show that there occurs a dynamic strain aging (DSA) phenomenon during deformation of AZ91D magnesium alloy in certain ranges of temperature and strain rate. The typical characteristics of DSA include serrated flow, the corresponding related serrated types are defined as type A and type A+B. Negative strain-rate sensitivity and peak of work-hardening rate appear. The critical plastic strain for the onset of serrations decreases with increasing deformation temperature, while it increases with increasing strain rate. Moreover, the work-hardening rate increases sharply with increasing temperature when the deformation temperature is higher than 323 K, and reaches the peak value at 368 K.

Key words: AZ91D wrought magnesium alloy; dynamic strain aging; serrated yielding; negative strain-rate sensitivity; work-hardening rate

许多工业上常用的合金在塑性变形过程中会出现不稳定流变,其拉伸曲线不再光滑而表现反复的锯齿这种现象是由于动态应变时屈服流变。研究表明[1 3],效(Dynamic strain aging,简称DSA)效应引起的,动态应变时效的本质是运动的位错和扩散的溶质原子交互作用的结果。迄今为止,大多数研究主要是针对低碳

基金项目:国家自然科学基金资助项目(50441013) 收稿日期:2009-09-29;修订日期:2010-02-01

通信作者:陈文哲,教授,博士;电话:0591-22863009;E-mail:chenwz@http://www.wendangwang.com

钢和面心立方合金产生此效应的宏观现象、影响因素、但对微观组织、产生的机理和各种模型进行研究[3 8], 密排六方结构材料DSA的研究报道还比较少见[9 11]。

镁合金的比强度和比刚度均优于钢及铝合金,且具有良好的减震降噪性能、电磁屏蔽性能、机械加工性能和易于回收等优点,被广泛应用于汽车、航空领

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