The solidification characteristics and segregation behavior of Cu-15Ni-8Sn alloy were systematically investigated in the present study. The solidification characteristics were revealed with the assistance of a solidification quenching experiment, DTA analysis and Scheil simulation. The solidification microstructure of Cu-15Ni-8Sn alloy was characterized by SEM, and the results indicated that the as-cast microstructure of Cu-15Ni-8Sn alloy mainly consists of Sn-depleted α-Cu(Ni,Sn) matrix, Sn-rich γ phase and lamellar (α + γ) structure. It has been demonstrated that the solidification process begins with the nucleation and growth of primary Sn-depleted α₁ phase (\( L \to \alpha_{1} \) at 1114 °C) and terminates with the divorced eutectic reaction (\( L_{2} \to \alpha_{2} + \gamma \) at 868 °C). During the subsequent cooling process, the discontinuous precipitation (\( \alpha_{2} \to \alpha_{1} + \gamma \)) takes place in the temperature range from about 700 °C to 600 °C. In addition, the macrosegregation behavior of Sn in Cu-15Ni-8Sn alloy was investigated by adopting vertical unidirectional solidification and measuring the cooling curves at different positions. The results indicated that an inverse macrosegregation of Sn solute exists in the as-prepared ingot, which mainly segregates at the chill surface of the alloy ingot. Namely, the Sn content is higher than 8 wt pct at the chill surface and about 8 wt pct inside the ingot for Cu-15Ni-8Sn alloy.

中文翻译：

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Cu-15Ni-8Sn合金的凝固特性和偏析行为

本文系统研究了Cu-15Ni-8Sn合金的凝固特性和偏析行为。借助凝固淬火实验，DTA分析和Scheil模拟揭示了凝固特性。用SEM对Cu-15Ni-8Sn合金的凝固组织进行了表征，结果表明Cu-15Ni-8Sn合金的铸态组织主要由贫锡α - Cu（Ni，Sn）基体，Sn-组成。富集的γ相和层状（α  +  γ）结构。已经证明的是，凝固过程中与成核和初级的生长开始的Sn-贫α _1个相（\（在1114°C时L至\ alpha_ {1} \）并以离婚的共晶反应终止（在868°C时L \ {L_ {2} \至\ alpha_ {2} + \ gamma \）。在随后的冷却过程中，不连续的降水（\（\ alpha_ {2} \ to \ alpha_ {1} + \ gamma \））发生在约700°C至600°C的温度范围内。此外，通过采用垂直单向凝固并测量不同位置的冷却曲线，研究了Sn在Cu-15Ni-8Sn合金中的宏观偏析行为。结果表明，所制备的铸锭中存在锡溶质的逆宏观偏析，其主要偏析于合金锭的冷硬表面。即，对于Cu-15Ni-8Sn合金，在冷硬表面的Sn含量高于8wt％，在铸锭内部的Sn含量高于8wt％。