Impact of P and Sr on solidification sequence and morphology of hypoeutectic Al-Si alloys: Combined thermodynamic computation and phase-field simulation
Impact of P and Sr on solidification sequence and morphology of hypoeutectic Al-Si alloys: Combined thermodynamic computation and phase-field simulation
复制标题
DOI：
10.1016/j.actamat.2015.06.056
复制
发表时间：
2015-10-01
期刊：
影响因子：
9.4
通讯作者：
Schmid-Fetzer, Rainer
中科院分区：
文献类型：
--
作者：
Eiken, Janin;Apel, Markus;Schmid-Fetzer, Rainer
即使少量的磷和锶也会强烈影响亚共晶铝硅合金的微观结构。 P 是商业铝合金中不可避免的微量元素，它会导致 AlP 颗粒的形成，作为共晶 (Si) 的有效成核位点。相比之下，特意添加 Sr 是为了将共晶 (Si) 的形态改变为细珊瑚状纤维。据推测，Sr 不仅会改变 (Si) 的生长动力学，而且还可以防止由于 Al2Si2Sr 形成中和 AlP 颗粒而导致的有害 (Si) 成核。这假定 AlP 和 Al2Si2Sr 均先于 (Si) 沉淀。使用新评估的 Al-Si-Sr-P 系统热力学数据库，在平衡和 Scheil 条件下评估并绘制了 AlP 和 Al2Si2Sr 硅前形成的临界 P 和 Sr 阈值。通过3D相场模拟进一步研究了AlP、Al2Si2Sr和(Si)的竞争析出及其对共晶形貌演化的影响。 (Si) 界面迁移率的有效各向异性函数考虑了 Sr 诱导的内部孪晶。根据选择亚临界还是超临界的 P 和 Sr 含量，可以再现精细层状结构、粗片状结构或目标精细纤维共晶结构。 (C) 2015 Acta Materialia Inc. 由 Elsevier Ltd 出版。保留所有权利。
Even small amounts of Phosphorus and Strontium strongly affect the microstructure of hypoeutectic Al-Si alloys. P is an unavoidable trace element in commercial Al-alloys which causes formation of AlP particles as potent nucleation sites for eutectic (Si). Sr, in contrast, is purposely added to modify the morphology of eutectic (Si) towards fine coral-like fibers. It is hypothesized that Sr does not only alter the growth kinetics of (Si), but additionally prevents detrimental (Si) nucleation due to neutralization of AlP particles by Al2Si2Sr formation. This presumes that both AlP and Al2Si2Sr precipitate prior to (Si). Using a newly assessed thermodynamic database for the Al-Si-Sr-P system, critical P and Sr thresholds for pre-silicon formation of AlP and Al2Si2Sr were evaluated and mapped under equilibrium and Scheil conditions. The competitive precipitation of AlP, Al2Si2Sr and (Si) and its impact on the evolution of the eutectic morphology was further studied by 3D phase-field simulations. Effective anisotropy functions for the (Si) interface mobility considered Sr-induced internal twinning. Depending on whether subcritical or supercritical P and Sr contents were selected, either a fine lamellar structure, a coarse flaky structure, or the targeted fine fibrous eutectic structure was reproduced. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.