Xu Feng, Xiong Feiyu, Li Ming-Jian, Lian Yanping
Institute of Advanced Structure Technology, Beijing Institute of Technology, Beijing 100081, China.
Materials (Basel). 2022 Sep 30;15(19):6800. doi: 10.3390/ma15196800.
The grain structure of the selective laser melting additive manufactured parts has been shown to be heterogeneous and spatially non-uniform compared to the traditional manufacturing process. However, the complex formation mechanism of these unique grain structures is hard to reveal using the experimental method alone. In this study, we presented a high-fidelity 3D numerical model to address the grain growth mechanisms during the selective laser melting of 316 stainless steel, including two heating modes, i.e., conduction mode and keyhole mode melting. In the numerical model, the powder-scale thermo-fluid dynamics are simulated using the finite volume method with the volume of fluid method. At the same time, the grain structure evolution is sequentially predicted by the cellular automaton method with the predicted temperature field and the as-melted powder bed configuration as input. The simulation results agree well with the experimental data available in the literature. The influence of the process parameters and the keyhole and keyhole-induced void on grain structure formation are addressed in detail. The findings of this study are helpful to the optimization of process parameters for tailoring the microstructure of fabricated parts with expected mechanical properties.
与传统制造工艺相比，选择性激光熔化增材制造零件的晶粒结构已被证明是不均匀且空间上非均匀的。然而，仅使用实验方法很难揭示这些独特晶粒结构的复杂形成机制。在本研究中，我们提出了一个高保真三维数值模型，以解决316不锈钢选择性激光熔化过程中的晶粒生长机制，包括两种加热模式，即传导模式和小孔模式熔化。在数值模型中，使用有限体积法和流体体积法模拟粉末尺度的热流体动力学。同时，通过元胞自动机方法，以预测的温度场和熔化后的粉末床构型作为输入，依次预测晶粒结构的演变。模拟结果与文献中的实验数据吻合良好。详细讨论了工艺参数以及小孔和小孔诱导孔隙对晶粒结构形成的影响。本研究结果有助于优化工艺参数，以定制具有预期力学性能的制造零件的微观结构。
