5456铝合金PLC效应的两种临界机制研究
收稿日期: 2012-05-14
修回日期: 2012-07-22
网络出版日期: 2012-12-11
基金资助
国家重点基础研究发展计划项目2011CB302105, 国家自然科学基金项目51271174, 11072233和11102201及中国博士后科学基金项目20100480684资助
STUDY ON TWO CRITICAL MECHANISMS OF PLC EFFECT OF 5456 Al–BASED ALLOY
Received date: 2012-05-14
Revised date: 2012-07-22
Online published: 2012-12-11
Supported by
Supported by National Basic Research Program of China (No.2011CB302105), National Natural Science Foundation of China (Nos.51271174, 11072233 and 11102201) and China Postdoctoral Science Foundation (No.20100480684)
在不同温度下对5456铝合金进行拉伸实验, 观察到低温下的正常临界行为和高温下的反常临界行为. 对比不同温度下的应力--应变曲线, 分别定义上下包络线. 临界应变之前的应力在低温时遵循下包络线, 在高温时遵循上包络线. 锯齿状应力-应变曲线在上下包络线之间振荡, 且在低温时, 锯齿方向朝上; 高温时锯齿方向朝下. 通过对应力和微观位错运动的分析讨论, 提出了分别对应于上下包络线的2种稳定塑性变形, 并给出相应的位错运动情况: 下包络线对应着位错没有被溶质原子钉扎,上包络线对应着一部分位错已经被溶质原子钉扎但未能脱钉. 正常临界行为取决于第一次钉扎, 而反常临界行为取决于第一次脱钉.
关键词： 5456铝合金; Portevin-Le Chatelier (PLC) 效应; 动态应变时效; 位错; 拉伸实验
符师桦 程腾 张青川 曹鹏涛 胡琦 . 5456铝合金PLC效应的两种临界机制研究[J]. 金属学报, 2012 , 48(12) : 1453 -1458 . DOI: 10.3724/SP.J.1037.2012.00270
The normal critical behavior at low temperature and inverse critical behavior at high temperature of 5456 Al–based alloy were observed via tension tests at different temperatures. By comparing the stress–strain curves at different temperatures, the lower and upper envelope curves were identified. Before the critical strain, the stress followed the lower envelope curve at low temperature while followed the upper envelope curve at high temperature. The subsequent serrations, which were upward at low temperature but downward at high temperature, waved between the two envelope curves. Furthermore, in relation with stress and dislocation motion, two types of dislocation motion for stable plasticity corresponding to the upper and lower envelope curves were presented, respectively. The lower envelope curve implied few dislocations were pinned by solute, while the upper envelope curve implied some dislocations were pinned by solute prior to escape. Finally, two critical mechanisms were proposed that the critical strain depended on the first pinning process in normal behavior and on the first unpinning process in inverse behavior.
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