The role of strontium in modifying aluminium-silicon alloys
The role of strontium in modifying aluminium-silicon alloys
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DOI：
10.1016/j.actamat.2012.03.031
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发表时间：
2012-05-01
期刊：
影响因子：
9.4
通讯作者：
Banhart, J.
中科院分区：
文献类型：
--
作者：
Timpel, M.;Wanderka, N.;Banhart, J.
少量的锶可以将存在于Al-Si铸造合金中的共晶硅相的形态从粗片状转变为细纤维状网络。为了理解这一工业上重要但迄今尚未充分理解的效应，通过原子探针层析成像以原子分辨率和通过透射电子显微镜以纳米分辨率研究了锶分布。联合调查表明，Sr共偏析与Al和Si的共晶Si相。发现了两种类型的偏析：（i）纳米薄棒状共偏析的类型I是负责在Si晶体中形成多个孪晶，并使其在不同的结晶方向上的生长;（ii）类型II偏析来作为更扩展的结构，限制Si晶体的生长，并控制其分支。我们展示了Sr如何使先前在文献中假设的两种机制，即“杂质诱导的孪生”（通过I型）和共晶Si相的生长限制（通过II型）。(C)2012 Acta Materialia Inc.由Elsevier Ltd.出版。保留所有权利。
Small amounts of strontium can transform the morphology of the eutectic silicon phase present in Al-Si casting alloys from coarse plate-like to fine fibrous networks. In order to understand this industrially important but hitherto insufficiently understood effect, the strontium distribution was studied in atomic resolution by atom probe tomography and in nanometre resolution by transmission electron microscopy. The combined investigations indicate that Sr co-segregates with Al and Si within the eutectic Si phase. Two types of segregations were found: (i) nanometre-thin rod-like co-segregations of type I are responsible for the formation of multiple twins in a Si crystal and enable its growth in different crystallographic directions; (ii) type II segregations come as more extended structures, restrict growth of a Si crystal and control its branching. We show how Sr enables both kinds of mechanisms previously postulated in the literature, namely "impurity-induced twinning" (via type I) and growth restriction of eutectic Si phase (via type II). (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.