Melting or re-melting accompanies solidification in many technical castings. For example, during ingot casting, some crystal fragments or equiaxed grains can enter the superheated region and re-melt, while solidification continues in other regions. Solidification and remelting occurring simultaneously at different locations present an important species/energy transport mechanism, which impacts the structural/compositional homogeneity of the castings. The re-melting is typically understood as a reduction in the equiaxed grain size, but it can also lead to the destruction (disappearance) of equiaxed grains. Existing process-based models cannot treat the solidification/melting by considering both grain nucleation and destruction properly. Therefore, a new model is proposed based on a two-phase volume-average approach. In this model, nucleation of equiaxed grains occurs when inoculants (free growth sites) are activated by undercooling, while destruction of equiaxed grains occurs only when the equiaxed grains are completely re-melted by superheating. The mass, momentum, species, and enthalpy conservation equations are solved for the solidification/melting. The transport equations for the number densities of equiaxed grains and inoculants are calculated separately. A test casting (Al–7 wt.% Si) is calculated to illustrate the modelling features. This study improves understanding of grain melting and grain destruction as well as their impact on the as-solidified structure.

在许多技术铸件中，熔化或重熔都伴随着凝固。例如，在铸锭期间，一些晶体碎片或等轴晶粒可以进入过热区域并重新熔化，而在其他区域则继续凝固。同时发生在不同位置的凝固和重熔呈现出重要的物种/能量传输机制，这会影响铸件的结构/组成均匀性。重熔通常被理解为等轴晶粒尺寸的减小，但是它也可能导致等轴晶粒的破坏（消失）。现有的基于过程的模型无法通过同时考虑晶粒成核和破坏来处理凝固/熔化。因此，提出了一种基于两阶段体积平均方法的新模型。在这个模型中 当通过过冷激活孕育剂（自由生长部位）时，等轴晶核就发生了，而等轴晶的破坏只有在过热使等轴晶完全融化时才会发生。求解质量，动量，种类和焓守恒方程，以进行固化/熔化。等轴晶粒和孕育剂数量密度的传输方程是分别计算的。计算了一个试验铸件（Al–7 wt。％Si）以说明建模特征。这项研究提高了对晶粒熔化和晶粒破坏及其对凝固组织的影响的理解。求解凝固/熔化的动量，种类和焓守恒方程。等轴晶粒和孕育剂数量密度的传输方程是分别计算的。计算了一个试验铸件（Al–7 wt。％Si）以说明建模特征。这项研究提高了对晶粒熔化和晶粒破坏及其对凝固组织的影响的理解。求解凝固/熔化的动量，种类和焓守恒方程。等轴晶粒和孕育剂数量密度的传输方程是分别计算的。计算了一个试验铸件（Al–7 wt。％Si）以说明建模特征。这项研究提高了对晶粒熔化和晶粒破坏及其对凝固组织的影响的理解。