Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al-Mg alloys
Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al-Mg alloys
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DOI：
10.1016/j.actamat.2011.11.044
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发表时间：
2012-02-01
期刊：
影响因子：
9.4
通讯作者：
Fan, Z.
中科院分区：
文献类型：
--
作者：
Li, H-T.;Wang, Y.;Fan, Z.
研究了通过改变Mg含量和施加熔体强剪切细化Al-Mg合金晶粒的机理。结果表明，在正常熔炼条件下，Al-Mg合金中形成的氧化物为MgAl_2O_4，其形貌为等轴状，{111}面作为自然表面暴露出来。取决于Mg含量，MgAl 2 O 4颗粒在稀Al-Mg合金（Mg < 1 wt.%）中以氧化膜形式存在，或在更浓的Al-Mg合金（Mg > 1wt%）中作为自然分散的离散颗粒。这种MgAl 2 O 4颗粒可以作为α-Al晶粒成核的有效位点，MgAl_2O_4和α-Al之间存在良好的立方对立方取向关系。Al-Mg合金中增强的异质形核可以归因于晶格失配度为1.4%的MgAl_2O_4颗粒的高效力MgAl 2 O 4颗粒的数密度增加是由于Mg含量的增加而自然分散或通过强烈的熔体剪切而强制分散。研究还发现，强烈的熔体剪切导致显着的晶粒细化稀Al-Mg合金的有效分散的MgAl 2 O 4颗粒截留在氧化物膜，但它有边际效应的晶粒细化浓缩Al-Mg合金，其中MgAl 2 O 4颗粒已自然分散成单个颗粒的Mg含量的增加。(C)2011 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The mechanisms involved in the grain refinement of Al-Mg alloys through varying the Mg content and applying intensive melt shearing were investigated. It was found that the oxide formed in Al-Mg alloys under normal melting conditions is MgAl2O4, which displays an equi-axed and faceted morphology with {1 1 1} planes exposed as its natural surfaces. Depending on the Mg content, MgAl2O4 particles exist either as oxide films in dilute Al-Mg alloys (Mg < 1 wt.%) or as naturally dispersed discrete particles in more concentrated Al-Mg alloys (Mg > 1 wt.%). Such MgAl2O4 particles can act as potent sites for nucleation of alpha-Al grains, which is evidenced by the well-defined cube-on-cube orientation relationship between MgAl2O4 and alpha-Al. Enhanced heterogeneous nucleation in Al-Mg alloys can be attributed to the high potency of MgAl2O4 particles with a lattice misfit of 1.4% and the increased number density of MgAl2O4 particles due to either natural dispersion by the increased Mg content or forced dispersion through intensive melt shearing. It was also found that intensive melt shearing leads to significant grain refinement of dilute Al-Mg alloys by effective dispersion of the MgAl2O4 particles entrapped in oxide films, but it has marginal effect on the grain refinement of concentrated Al-Mg alloys, where MgAl2O4 particles have been naturally dispersed into individual particles by the increased Mg content. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.