In additive manufacturing (AM), the microstructure evolution is rather complex and plays a critical role in the mechanical performance. To predict the microstructure, many numerical models have been proposed, but solid-state phase transformations are usually not incorporated. In this work, we develop a Cellular Automaton (CA) model to simulate the solid-state phase transformation with alloy element partition. In this model, a mixed-mode phase transformation model is used, and both the growth and decomposition of precipitates are included. With the temperature profile from the validation experiment, the model well reproduces the precipitation process in the solidified Al 2024 alloy during Electron Beam Selective Melting (EBSM). The simulation results are in good agreement with the experimental results and illustrate the causes of some critical morphological features. The impact of temperature profile on the precipitation process is studied and the results indicate: (1) the rising of the powder-bed temperature during the fabrication process might cause precipitate decomposition; (2) the precipitates are evenly distributed and their sizes are uniform when the powder-bed temperature is low.

在增材制造（AM）中，微观结构的演变相当复杂，并且在机械性能方面起着至关重要的作用。为了预测微观结构，已经提出了许多数值模型，但是通常不包含固态相变。在这项工作中，我们开发了一个细胞自动机（CA）模型来模拟合金元素分配的固态相变。在该模型中，使用了混合模式相变模型，并且包括了沉淀物的生长和分解。利用验证实验中的温度曲线，该模型很好地再现了电子束选择性熔化（EBSM）过程中凝固的Al 2024合金中的沉淀过程。仿真结果与实验结果吻合良好，并说明了某些关键形态特征的原因。研究了温度分布对析出过程的影响，结果表明：（1）制备过程中粉末床温度的升高可能引起析出物的分解；（2）粉末床温度低时，析出物分布均匀，粒径均匀。