A method based on the centroid of segregation points: A Voronoi polygon application to solidification of alloys
A method based on the centroid of segregation points: A Voronoi polygon application to solidification of alloys
复制标题
基于偏析点质心的方法：Voronoi 多边形在合金凝固中的应用
DOI：
10.1016/j.jallcom.2018.05.160
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发表时间：
2018-09-25
影响因子：
6.2
通讯作者：
Chang, Yi
中科院分区：
文献类型：
--
作者：
Hou, Zibing;Guo, Dongwei;Chang, Yi
利用Voronoi多边形法建立了一种基于合金宏观组织中独立偏析点质心的精细偏析控制新方法。发现Voronoi多边形面积近似服从对数正态分布，这表明一个多边形可能反映了一个新的凝固单元。研究了不同位置的Voronoi多边形特征与碳偏析程度(偏析比)的关系。在纯柱状晶区，偏析程度随着Voronoi多边形尺寸的减小而恶化；在等轴晶区，偏析程度随着尺寸的增大而恶化。研究了多边形在不同条件下的近平衡凝固模型，其结果与上述偏析比的结果是一致的。与二次臂间距相比，凝固组织的分维可以更好地描述凝固组织的特征和相应偏析时Voronoi多边形的尺寸变化。因此，本研究提出了一种新的实验方法，从一个不同的角度来描述宏观组织，即用偏析点代替凝固组织。凝固过程中偏析产生的Voronoi多边形的形成应分为两个阶段，即偏析点的出现和多边形轮廓的确定。可以通过改变相应的Voronoi多边形的尺寸来控制偏析程度，这是一种独特的改善元素分布均匀性的替代策略，而不是像偏析形成的复杂过程那样同时考虑形核形成、凝固组织生长和液体流动。(C)2018爱思唯尔B.V.保留所有权利。
A new method for controlling segregation delicately based on the centroid of independent segregation points in an alloy macrostructure is established using Voronoi polygon method. Voronoi polygon area is found to nearly obey the log-normal distribution, which shows that a polygon may reflect a new solidifying unit. The relationship between Voronoi polygon characteristics and carbon segregation extent (segregation ratio) is investigated at different locations. In a pure columnar grain zone, the segregation extent worsens as the Voronoi polygon size decreases; in an equiaxed grain zone, this extent worsens as the size increases. A near-equilibrium solidification model for polygons under different conditions is studied, and the results are consistent with the aforementioned finding of segregation ratio. Compared with a secondary arm spacing, the fractal dimension of the solidification structure may be a better method to describe the characteristics of the solidification structure and the size change of Voronoi polygons as to relevant segregation. Thus, this study proposes a new experimental method that depicts the macrostructure from a different perspective, i.e., the segregation point instead of the solidification structure. The formation of Voronoi polygons created by segregation points during solidifying should be divided into two stages, i.e., appearance of the segregation point and determination of the polygon's outline. The segregation extent can be controlled by altering the size of the relevant Voronoi polygon, which is a unique alternative strategy for improving the uniformity of element distribution rather than simultaneously considering nucleus formation, solidification structure growth, and liquid flow as to the complex process of segregation formation. (C) 2018 Elsevier B.V. All rights reserved.