Li Jiehua, Hage Fredrik, Wiessner Manfred, Romaner Lorenz, Scheiber Daniel, Sartory Bernhard, Ramasse Quentin, Schumacher Peter
Institute of Casting Research, Montanuniversität Leoben, Leoben, A-8700, Austria.
SuperSTEM Laboratory, SciTech Daresbury Campus, Keckwick Lane, Daresbury, WA4 4AD, UK.
Sci Rep. 2015 Sep 2;5:13802. doi: 10.1038/srep13802.
Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism, and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si.
控制共晶硅的生长并将其从片状转变为纤维状是改善铝硅合金性能的关键因素。迄今为止，普遍认为杂质诱导孪晶（IIT）机制、孪晶面再入边（TPRE）机制以及TPRE机制的中毒现象在某些条件下是有效的。然而，IIT、TPRE或TPRE机制的中毒现象并不能解释所有的观察结果。在此，我们报告了一项关于铕在铝硅合金中共晶硅生长过程中作用的原子尺度实验和理论研究。实验和理论研究均揭示了三种不同的作用：（i）在硅晶面交界处吸附，诱导IIT机制；（ii）在孪晶面再入边吸附，诱导TPRE机制或TPRE机制的中毒现象；（iii）在生长的硅孪晶前方偏聚，导致共晶硅内溶质夹带。这项研究不仅为广为接受的TPRE和IIT机制中毒现象提供了直接的实验支持，还全面阐述了铕原子在共晶硅生长过程中的作用，包括共晶硅内的溶质夹带。
