Al-10Mg 合金热压缩过程中项链组织的形成和扩展行为

Necklace Structure Formation and Expansion Behavior In an Al-10Mg Alloy During Hot Uniaxial Compression

摘要:

本文采用旋转结晶工艺制备高镁含量的Al-10Mg合金坯料、并对其进行673K/24h固溶处理及单轴热压缩变形。通过流变应力行为及微观组织表征来分析合金动态再结晶过程中项链组织的形核及扩展行为,特别地,分析了变形温度和应变率对项链组织扩展行为的不同影响。研究表明：大角度晶界的凸出是项链组织首层再结晶晶粒的形核方式, Al-10Mg合金变形组织中有微带、应变诱发的小角度晶界和回复形成的小角度晶界等三种亚晶界。随变形温度升高,微带和回复形成的小角度晶界逐渐消失,应变诱发的小角度晶界形核及由大角度晶界迁移造成的再结晶晶粒粗化是项链组织扩展的主要方式；随应变率的降低,未再结晶的变形晶粒被划分为低取向差中心区、外层再结晶晶粒区和处于中间层的富集小角度晶界的网状结构区等三部分,应变率从6.94×10_-1/s降至6.94×10_-2/s时再结晶晶粒面积占比减小,而当应变率从6.94×10_-2/s进一步降至6.94×10_-3/s时,再结晶晶粒面积占比显著提高。

Abstract:

The formation and expansion of necklace structure in an Al-10Mg alloy have been studied. The alloy was produced by centrifugal casting, which was followed by 673K/24h solid solution treatment and hot uniaxial compression. The different effects of temperature and strain rate on expansion of necklace structure were especially clarified. In this study, bulging is the nucleation type of first layer in necklace structure, and three different types of subboundary were found in the deformation microstructure of Al-10Mg alloy. When temperature increased, microband and recovered subboundary were gradually eliminated, after which strain-induced subboundary nucleation and recrystallized grain coarsening became a main way of necklace expansion. When strain rate decreased, low angle grain boundary was accumulated. Three regions denoted by low misorientation region in interior, new grains in out layer and net structure of subboundary concentration region in middle were observed in non-recrystallized grains. The proportion of recrystallized grain area decreased when strain rate changed from 6.94×10_-1/s to 6.94×10_-2/s, then significantly increased when strain rate changed from 6.94×10_-2/s to 6.94×10_-3/s.