As a typical solidification microstructure, anomalous eutectic is still not known of its growth mechanism. Mullis et al (2018, Acta Mater. 145:186) experimentally showed that the volume faction of anomalous eutectic was not consisted with the predictions by any model invoking partial remelting of primary solidified microstructure. In the present article, the anomalous eutectic microstructure of Ni–Sn alloy solidified from undercooled melts and laser remelting melt pool has been investigated through experiments and cellular automaton (CA) simulations. Computational and experimental results showed that the nucleated α-Ni particulates grew into globular, lamellar or ‘tadpole’ morphology. The ‘tadpole’ morphology, which has a globular ‘head’ and a lamellar ‘tail’, is an intermediate pattern between globular and lamellar morphologies, and would be seen as an evidence of the globular to lamellar transition (GLT). The occurrence of the GLT or not determines that the solidified microstructure is either anomalous eutectic or lamellar eutectic. CA simulations showed that the GLT was mainly influenced by the temperature gradient G and pulling velocity V . For positive G and V , representing the directional solidification at the bottom of melt pool, the GLT prefers to occur at high G and low V ; for negative G and V , which refers to the solidification in undercooled melts, the GLT prefers to occur at low absolute value of G and V . The GLT was also experimentally observed under 5Authors to whom any correspondence should be addressed. 0965-0393/20/065014+18$33.00 © 2020 IOP Publishing Ltd Printed in the UK 1 Modelling Simul. Mater. Sci. Eng. 28 (2020) 065014 W Lei et al the above two circumstances. The GLT growth mechanism abstained from CA simulations well explains the experimental results.

中文翻译：

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异常共晶生长过程中的球状到层状转变

异常共晶作为典型的凝固组织，其生长机制尚不清楚。Mullis 等人 (2018, Acta Mater. 145:186) 实验表明，异常共晶的体积分布与任何调用初级凝固微观结构部分重熔的模型的预测不符。在本文中，通过实验和元胞自动机 (CA) 模拟研究了过冷熔体和激光重熔熔池凝固的 Ni-Sn 合金的异常共晶组织。计算和实验结果表明，成核的 α-Ni 颗粒生长成球状、层状或“蝌蚪”形态。“蝌蚪”形态具有球状“头部”和层状“尾部”，是球状和层状形态之间的中间模式，并且将被视为球状到层状转变（GLT）的证据。GLT 的出现与否决定了凝固组织是异常共晶还是层状共晶。CA 模拟表明 GLT 主要受温度梯度 G 和拉速 V 的影响。对于正的 G 和 V ，代表熔池底部的定向凝固，GLT 倾向于发生在高 G 和低 V 处；对于负 G 和 V ，这指的是过冷熔体中的凝固，GLT 更倾向于在 G 和 V 的绝对值较低时发生。GLT 也在 5Authors 下进行了实验观察，任何通信都应向其发送。0965-0393/20/065014+18$33.00 © 2020 IOP Publishing Ltd 英国印刷 1 Modeling Simul。母校。科学。英。28 (2020) 065014 W Lei 等 对上述两种情况。从 CA 模拟中放弃的 GLT 生长机制很好地解释了实验结果。