AZ91镁合金中变形孪晶与析出相交互作用结构的电子显微学研究

Electron microscopy investigation on deformation⁃twin/precipitates interaction structures in an AZ91 alloy

本文综合利用透射电子显微镜(transmission electron microscopy,TEM)及高分辨透射电子显微镜(high resolution transmission electron microscope,HRTEM)电子显微表征技术,对冲击变形时效AZ91镁合金中变形孪晶与β⁃Mg17Al12析出相交互作用引发的变形结构进行了观察和表征。结果表明:(1)β析出相阻碍{1012}孪晶生长使其界面形成台阶结构导致孪晶板条呈现粗细不均的形貌,更严重的交互作用可导致孪晶界发生大角度弯折,同时诱发基体中扭折带的形成以协调孪晶变形;(2){1011}孪晶与β析出相的交互作用会产生局域应力集中,导致连锁诱发{1012}孪晶形核,表明孪晶与析出相的交互作用可以促进孪晶形核。

In this paper,the deformation microstructures induced by the interaction of different types of twins withβ⁃Mg17Al12 precipitates(β⁃phase)in shock⁃loaded AZ91 magnesium alloy was investigated by a combination of transmission electron microscope(TEM)and high resolution transmission electron microscope(HRTEM)techniques.The results show that:(1)the growth of{1012}twins can be hindered byβ⁃phases,and this will result in forming step structure at twin boundaries,such that twin laths appear to have uneven morphology.More severe twin/precipitate interaction can allow a twin boundary to be bent to a large angle with local kinking occurring to accommodate the local stress concentration.(2)The interaction between{1011}twin andβprecipitates can produce local stress concentration of high degree,to result in nucleation of{1012}twins in sequence,indicating that the interaction between twins and precipitates can promote the nucleation twinning.