The role of trace element segregation in the eutectic modification of hypoeutectic Al-Si alloys
The role of trace element segregation in the eutectic modification of hypoeutectic Al-Si alloys
复制标题
DOI：
10.1016/j.jallcom.2009.09.138
复制
发表时间：
2010-01-21
影响因子：
6.2
通讯作者：
Suzuki, Y.
中科院分区：
文献类型：
--
作者：
Nogita, K.;Yasuda, H.;Suzuki, Y.
亚共晶Al-Si合金中共晶硅的改性引起硅相从针状到细纤维形态的结构转变，并且在工业中广泛地进行以改善机械性能。已经证明，化学改性合金中的纤维硅相是严重孪晶的。有人提出，这种增加的孪晶密度的结果，从吸附的杂质元素在固液界面永久进一步增长，根据一个孪晶面凹边（TPRE）模型。在本文中，我们讨论了这种机制的共晶改性光同步辐射获得的实验数据和预测的基础上，理论计算。这项研究利用了mu-XIRF（X射线荧光）技术在SPring-8同步辐射设施的X射线源，并揭示了不同的元素，理论上满足几何要求的杂质引起的TPRE模型不具有相同的效果在凝固过程中的硅的生长。例如，铕相对均匀地分布在硅相中，而在硅相中根本没有发现镱。这对亚共晶铝硅合金共晶变质的基本机制具有重要意义。(C)2009 Elsevier B.V.保留所有权利。
Modification of the eutectic silicon in hypoeutectic Al-Si alloys causes a structural transformation of the silicon phase from a needle-like to a fine fibrous morphology and is carried out extensively in industry to improve mechanical properties. It has been documented that the fibrous silicon phase in chemically modified alloys is heavily twinned. It has been proposed that this increased density of twinning results from the adsorption of impurity-elements at the solid-liquid interface perpetuating further growth according to a twin plane re-entrant edge (TPRE) model. In this paper, we discuss this mechanism of eutectic modification in light of experimental data obtained by synchrotron radiation and predictions based on theoretical calculations. This research utilizes a mu-XIRF (X-ray fluorescence) technique at the SPring-8 synchrotron radiation facility X-ray source and reveals that different elements which theoretically satisfy the geometric requirements of the impurity-induced TPRE model do not have the same effect on the growth of silicon during solidification. Europium for instance is distributed relatively homogeneously in the silicon phase while ytterbium was not found in the silicon phase at all. This has important implications for the fundamental mechanisms of eutectic modification in hypoeutectic aluminium-silicon alloys. (C) 2009 Elsevier B.V. All rights reserved.