A hypereutectic alloy is a metallic alloy which has a composition beyond the eutectic point. As the temperature of a non-eutectic composition is lowered, the liquid mixture will precipitate one component of the mixture before the other. In the present paper, Ni–Si hypereutectic composites at the different solidification rates were prepared by a modified Bridgman directional solidification technique. Primary dendrite arm spacings of the Ni–Si hypereutectic composites were calculated at the different solidification rates according to Kurz–Fisher model, Hunt–Lu model and Trivedi model, respectively. Relation between micro-hardness and primary dendrite arm spacing was obtained. The selected area electron diffraction was adopted to confirm the preferential orientation of Ni–Si hypereutectic composites. It is found that primary dendrite arm spacing of the experimental results are very close to Kurz–Fisher model, while deviating from that predicted from Hunt–Lu model and Trivedi model. Therefore, Kurz–Fisher model is much more suitable to describe primary dendrite arm spacing of Ni–Si hypereutectic.

中文翻译：

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不同凝固速率下 Ni-Si 过共晶复合材料的初生枝晶臂间距和优先取向

过共晶合金是成分超过共晶点的金属合金。随着非低共熔组合物的温度降低，液体混合物将先于另一种成分沉淀混合物的一种成分。在本文中，采用改进的布里奇曼定向凝固技术制备了不同凝固速率下的 Ni-Si 过共晶复合材料。分别根据 Kurz-Fisher 模型、Hunt-Lu 模型和 Trivedi 模型计算了不同凝固速率下 Ni-Si 过共晶复合材料的初级枝晶臂间距。获得了显微硬度与一次枝晶臂间距之间的关系。采用选区电子衍射来确认 Ni-Si 过共晶复合材料的优先取向。发现实验结果的初级枝晶臂间距与Kurz-Fisher模型非常接近，而与Hunt-Lu模型和Trivedi模型的预测存在偏差。因此，Kurz-Fisher 模型更适合描述 Ni-Si 过共晶的初生枝晶臂间距。