Proper characterization of solute segregation during the solidification of alloys using partition coefficients (k) is essential to understand and model solidification paths and associated microstructural evolution. Traditional methods to determine k assume a constant value over the course of solidification, which leads to improper descriptions of segregation for elements with variable partitioning behavior. In this study, a novel method to determine partition coefficients as a function of fraction solid using electron probe microanalysis point grid measurements is described. The proposed method, termed the mass balance analysis (MBA), was applied to a cast 90 wt pct Co-10 wt pct Cu alloy with well-documented segregation behavior. The resultant partition coefficients indicated that k_Cu decreased as a function of fraction solid, while k_Co significantly increased in the terminal stage of solidification. The measured k values showed excellent agreement with those taken from the solidus and liquidus lines of Co-Cu binary phase diagram generated using Thermo-Calc. The MBA was also applied to a multicomponent austenitic commercial alloy. It showed a decrease in the partition coefficients for both Cr and Nb as a function of fraction solid and demonstrated the applicability of the MBA method to highly alloyed multicomponent systems.

在合金凝固过程中使用分配系数（k）正确表征溶质偏析对于理解和建模凝固路径及相关的微观结构演变至关重要。确定k的传统方法在凝固过程中采用恒定值，这导致对具有可变分配行为的元素的偏析的描述不正确。在这项研究中，描述了一种使用电子探针微分析点网格测量来确定作为分数固体函数的分配系数的新方法。所提出的方法被称为质量平衡分析（MBA），该方法用于铸件90 wt pct Co-10 wt pct Cu合金，具有良好的偏析行为。得出的分配系数表明：k _Cu随固相分数的降低而降低，而k _Co在凝固末期显着提高。测得的k值与使用Thermo-Calc生成的Co-Cu二元相图的固相线和液相线取得了极好的一致性。MBA还应用于多组分奥氏体商用合金。它显示出Cr和Nb的分配系数均随分数固体的降低而降低，并证明了MBA方法对高度合金化的多组分体系的适用性。