成核
过冷
材料科学
共晶体系
粒度
枝晶(数学)
微观结构
各向异性
合金
晶界
冶金
热力学
作者
Zhe Ren,Zhenpeng Pu,Dongrong Liu
标识
DOI:10.1016/j.commatsci.2021.111131
摘要
Control of grain size during solidification is an important issue according to the desired usage properties. In this study, both microstructure characterizations and numerical simulations are performed for as-cast hypoeutectic Al-Si alloys to understand the mechanism of grain-size transition with initial Si contents. An improved three-dimensional (3D) sharp-interface model is developed that couples cellular automaton (CA) approach with a deterministic mesh-anisotropy reduction (DMAR) algorithm. The improved sharp-interface model is able to accurately calculate interface curvature and reproduce reasonable dendrite morphology within a wide range of cooling rates. It is found that grain size first decreases with increasing the initial Si content to 3 wt% and then increases with further Si additions. The nucleation undercooling significantly increases with increasing the Si content from 3 wt% to 10 wt% due to a Si-poisoning effect. The grain-size transition is mainly determined by the variations in the nucleation undercooling. Analysis using the Interdependence model also supports that a wide nucleation-free-zone is formed during solidification of Al-10 wt% Si alloy induced by a large nucleation barrier and a decreased growth velocity.
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