Abstract In the present study, we employ a multiphase-field model based on the grand chemical potential formulation to simulate the microstructural transition in a binary FeSn monotectic alloy. In a directional solidification environment, we systematically investigate the formation of monotectic microstructures. At equilibrium monotectic composition, we observe that depending on the imposed temperature gradient and the solidification velocity, the liquid L2 phase transforms into an array of droplets embedded in the solid phase matrix. Initiated at the solidification front, the minor liquid phase undergoes detachment and spherodization to form L2 droplets as a result of post-solidification ripening behind the growth front. We show that the wavelength of the oscillating phase is critical to observe a lamellar to droplet transition. A microstructural selection map at various growth conditions is delineated to illustrate the different monotectic microstructures. The present phase-field simulations, while providing significant insights into the formation of microstructures closes the gap with the in-situ observations reported earlier. In addition, the influence of lamellar spacing is investigated in detail through the Jackson and Hunt analytical relationship for the present material system.

中文翻译：

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偏晶合金的显微结构转变：相场研究

摘要 在本研究中，我们采用基于大化学势公式的多相场模型来模拟二元 FeSn 偏晶合金的微观结构转变。在定向凝固环境中，我们系统地研究了偏晶微观结构的形成。在平衡单晶组成时，我们观察到根据施加的温度梯度和凝固速度，液态 L2 相转变为嵌入固相基质中的液滴阵列。在凝固前沿开始，由于生长前沿后面的凝固后成熟，次要液相经历分离和球化形成 L2 液滴。我们表明振荡相的波长对于观察层状到液滴的转变至关重要。描绘了不同生长条件下的微观结构选择图，以说明不同的偏晶微观结构。目前的相场模拟在提供对微观结构形成的重要见解的同时，缩小了与之前报道的原位观察结果的差距。此外，通过当前材料系统的 Jackson 和 Hunt 分析关系详细研究了层状间距的影响。