Al-Cu多晶合金中锯齿形屈服现象的时序统计研究

合金中溶质原子和可动位错之间的交互作用引起材料的固溶硬化,这一交互作用在合适的应变率和温度条件下可重复发生,称为动态应变时效(DSA),从而导致锯齿形的应力屈服,同时伴随着变形带的产生,被称为Portevin-Le Chartelier(PLC)效应。本文对Al-Cu多晶合金锯齿形屈服现象中应力跌幅、跌落时间等多个特征物理量时序演化规律进行了系统的研究。结果显示,跌落时间对应变不敏感;1mm和2mm厚度试件的应力跌幅和再加载时间都近似随应变线性增加,3mm厚试件的统计结果则显示出一个明显的转变点。最后本文结合动态应变时效原理和晶体位错学,分析了实验条件(应变率和试件尺寸)对各特征物理量的影响。

Temporal Statistical Analysis of Serrated Yielding in Al-Cu Polycrystals

The interaction of mobile dislocations with solute atoms results in solid solution hardening in dilute alloys.This interaction may repeat itself when the metallic solid solutions are subjected to the plastic deformation in a proper range of strain rate and temperature.It is commonly called as dynamic strain aging(DSA),which may lead to the occurrence of the Portevin-Le Chartelier (PLC) effect,known for its typical phenomenon including the serrated yielding and the emergence of the PLC band.In this paper,a systematic statistical analysis of the influence of the experimental conditions,including both the imposed strain-rate and the dimension of the samples,on the characteristics of this phenomenon,including the stress drop amplitude and the duration of the serration,etc.,has been carried out,considering the DSA principle and the dynamics of dislocation.Drop duration is found to be almost constant under particular conditions.The stress drops and the reloading time of the 1mm and 2mm thick samples approximately increase with strain,while these of the 3mm thick samples exhibit a prominent convertion.