Understanding Segregation to Predict Solidification
Solidification paths may be calculated from segregation equations, and may be used to pinpoint optimum alloy compositions for your castings.
GEOFFREY SIGWORTH, GKSENGINEERING SERVICES, DUNEDIN, FLORIDA 了解偏析 预测凝固
凝固路径可以通过偏析方程计算，并且可以用于确定铸件的最佳合金成分。 佛罗里达州，达尼丁，GKS 工程服务公司，Geoffrey SiGworth。
Tis article is the second in a two-part series on solidification in alu- minum castings. While the series focuses on solidification principles in aluminum alloys, many can be applied to other metals, as well.
there is a redistribution of alloying elements and impu- rities called segregation. Segregation has a significant influence on casting quality. Understanding the process is useful for the casting engineer or metallurgist. Te two types of segregation are microsegregation and macrosegregation. Microsegregation is the variation in composition on a very small scale: between dendrites and dendrite arms. Te Al-Cu alloy system
W
will be used to illustrate how segregation occurs. Researchers have examined this alloy system in great detail by researchers. It forms the basis for the high strength family of 2xx cast- ing alloys.
hen a metal is liquid, it is homoge- neous. That is, the metal properties (especially composition) are the same everywhere. However, during freezing
这篇文章是铝铸件凝固系列的第二部分。虽然该系列文章 着重于铝合金凝固原理，但是文章中许多原理也可应用到 其它金属。
当
金属处于液态时，它是均匀的。即各处的 金属特性（尤其是成分）都是相同的。然 而，凝固过程中存在合金元素及杂质的重
新分配，即偏析。偏析对铸件质量影响显著。了解这个 过程对铸造工程师或冶金学家十分有益。 偏析有两种类型即微观偏析和宏观偏析。微观偏析是 指在枝晶和枝晶臂之间非常微小范围内的成分偏差。 文章以Al-Cu合金系为例阐述偏析如何发生。研究人 员对该合金系开展了大量 详细的实验研究。奠定了 2xx高强度铸造合金系列 的基础。
图1所示是完整的 Al-Cu相图。该体系中有 许多金属间化合物。铝铸 造企业主要关图中（注： 该图指的是前面提到的图
Fig. 1. This is the Al-Cu phase diagram.
Al-Cu二元合金相图 54 |
FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION September 2014
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