技术论文和演示文稿

在固化多组分液体（金属合金，硫化物哑光或氧化物炉渣系统）期间，该过程不仅高于温度，而且还取决于组成。系统的热力学特性将决定液体及其组成的相或混合物与液体的原始组成不同，从而改变了未固化的剩余液体的组成。If the solidification process is fast enough so that the system doesn’t have time to equilibrate, then the solid that was created won’t participate on the subsequent solidification step and since the liquid composition has changed, then new phases will form with different composition than the previous solids. This is known as Scheil cooling, or real solidification as it is highly unlikely that the solids will have sufficient time to equilibrate with the remaining liquid before the temperature continues to decrease during a real solidification process. The challenge is that at each time step, the composition of the remaining liquid and the new solids forming is changing, therefore, changing the shape of the “solid fraction” function that is required to model phase change. The new “solid fraction” depends on the thermodynamic properties of the system which in many real cases correspond to a non-ideal chemical solution. In this paper, a combined thermodynamic and multiphysics model was used to simulate this process using COMSOL Multiphysics® software and M4Dlib [1]. A transient heat transfer and fluid flow model in the COMSOL® software was used to model temperature and phase change of a liquid metal alloy, whereas the composition and solid fraction functions were calculated at every time step using M4Dlib, an external library of thermodynamic properties.

图1显示了在固体过程中固体和液相的组成，这是累积固体分数的函数，用于XB = 0.1的初始液体组成。与“平衡”固化案例相比，最后一个固体到沉淀的浓度比原始液体高得多。

将结果与三种情况进行了比较：一个简单的相变模型，平衡固化案例和用于Scheil冷却的分析解决方案。从M4DLIB的固体组成与经典Scheil方程的比较如图2所示。最后，计算出的固体分数功能与温度相对于温度如图3所示，在图3中，固化过程在液相液体温度下开始（tLileSUS = 1227.53K），但在1053.25K处最终确定，该液体的初始组成远低于Solidus温度（TSolidus = 1176.6K xb = 0.1）。

使用COMSOL®软件和M4DLIB提供的组合多物理学和热力学模型的优点在于，分析Scheil冷却方程的某些假设不一定在依赖空间的情况下维持。最后，从M4DLIB计算液相的浓度变化速率，并且可以通过源项耦合到传质模型。