合金材料锯齿形塑性失稳的实验研究与机理分析

Experimental study and mechanism analysis of the serrated plastic instability of alloy materials

轻质高强度合金具有重要的应用背景,而其机理仍未解明的锯齿型塑性失稳现象制约了它们的应用,同时该问题也是材料科学家关注的一个热点问题.基于实验力学的研究,作者所属的光测细观力学课题组提出用动态散斑方法研究合金材料锯齿形屈服剪切带,观察到带形成演化和传播的时空特征、带内应变动态分布和剪切带雪崩变形时拉伸试件的瞬态收缩变形;用固溶处理方法调节合金材料内部溶质原子浓度和析出纳米相颗粒大小与分布,观察到随之变化的锯齿与剪切带的时空特征演变,发现了溶质原子浓度与析出相颗粒这两种因素分别在不同固溶处理温度对动态应变时效起主导作用;建立了基于溶质原子与位错交互作用的物理唯象模型,得到不同加载应变率下与实验相符的锯齿形加载曲线,再现出锯齿形加载曲线和带反复传播的轨迹.

Lightweight high strengm alloys with still unclear mechanism restricts its application and attracts the attention of material scientists. Based on the research of experimental mechanics, the author＇s group proposed using speckle method to observe the shear band formation, evolution and propagation, obtained the deformation distribution in inner band and found the transient shrinkage deformation outside the shear band when an avalanche shearing deformation in the band occurs. With solute treat method to adjust the concentration of solute atoms and the particle size of precipitated phase, the corresponding changes of serrated features and spatial-tempo characteristics of band propagation were observed. They show that the concentration of solute atoms or the particle size of the precipitated phase respectively has a dominant effect on dynamic strain aging （DSA） under different solute treat temperatures. A phenomenological model based on the dynamic interaction between dislocation and diffusing solutes was developed to investigate the PLC （Portevin-Le Chatelier） effect with an emphasis on the mechanical response of the structure evolution at the microscopic scale, and three types of PLC effects at different applied strain rates were reproduced when the spatial coupling was included.