Continuous and discontinuous grain coarsening in a fine-grained particle-containing Al-Sc alloy
Continuous and discontinuous grain coarsening in a fine-grained particle-containing Al-Sc alloy
复制标题
DOI：
10.1016/j.actamat.2004.11.006
复制
发表时间：
2005-02-01
期刊：
影响因子：
9.4
通讯作者：
Humphreys, FJ
中科院分区：
文献类型：
--
作者：
Ferry, M;Hamilton, NE;Humphreys, FJ
对Al-0.2wt%Sc合金进行固溶处理，通过等通道角挤压（ECAP）变形至9.2的有效真应变，然后在350 ℃下时效3小时，以产生包含大部分（类似于0.7）的大角度晶界（HAGB）的细晶粒（0.8 μ m直径）显微组织。该老化处理还产生了5 nm直径的Al 3Sc颗粒的相对均匀的分散。使用SEM、EBSD和TEM研究了在高达550 ℃的温度下的晶粒稳定性。结果表明，在500 ℃以下，细晶组织非常稳定，晶粒逐渐粗化，晶粒尺寸分布、织构和晶界特征无明显变化。这种均匀的粗化行为通常称为连续再结晶。在此制度下，细晶粒组织和Al 3Sc颗粒都表现出三级粗化动力学，dR/dt与dr/dt成比例，这表明晶粒粗化受颗粒生长速率控制，后者受钪在Al基体中的体扩散控制。在500 ℃下的延长退火期间以及在更高温度下的短时间内，存在从连续到不连续的晶粒粗化的显著过渡，由此少量晶粒快速生长以产生粗（>10 μ m）晶粒尺寸。一个分析平均场模型的晶粒粗化在含颗粒的合金被证明是充分预测这种转变的粗化行为。(C)2004 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
An Al-0.2 wt% Sc alloy was solution treated, deformed by equal channel angular pressing (ECAP) to an effective true strain of 9.2 then aged for 3 h at 350 degreesC to produce a fine-grained (0.8 mum diameter) microstructure containing a large fraction (similar to0.7) of high angle grain boundaries (HAGBs). This ageing treatment also generated a relatively uniform dispersion of 5 nm diameter Al3Sc particles. Grain stability was investigated at temperatures up to 550 degreesC using SEM, EBSD and TEM. It was found that the fine-grain structure was remarkably stable at temperatures up to 500 degreesC with grain coarsening occurring gradually with no marked change in the grain size distribution, texture and grain boundary character. This homogeneous coarsening behaviour is usually termed continuous recrystallization. In this regime, both the fine-grained microstructure and Al3Sc particles exhibit third order coarsening kinetics with dR/dt proportional to dr/dt which indicates that grain coarsening is controlled by the rate of particle growth with the latter controlled by bulk diffusion of scandium in the Al matrix. During extended annealing at 500 degreesC and for short times at higher temperatures, there is a notable transition from continuous to discontinuous grain coarsening whereby a small number of grains grow rapidly to produce a coarse (>10 mum) grain size. An analytical mean field model of grain coarsening in particle-containing alloys was shown to adequately predict this transition in coarsening behaviour. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.