Metal matrix composite parts fabricated by additive manufacturing are of interest due to their fine grain structures and superior mechanical properties. In this study, a phase-field (PF) model is developed to simulate the grain evolution of TiB₂/316L stainless steel composite during the selective laser melting (SLM) process. The reinforcing TiB₂ particles are explicitly incorporated into the PF model, and the influences on grain evolutions are comprehensively considered, including the induced heterogeneous nucleation and the pinning effect on grain boundaries. The simulation results demonstrate that with the addition of TiB₂ particles, both columnar and equiaxed grains are formed in the scanning track. While the columnar grains are due to epitaxial growth from the molten pool boundary, the TiB₂ particles act as the nucleation sites inside the molten pool, resulting in the formation of equiaxed grains. The grain boundaries become complicated due to the pinning of grain boundaries by TiB₂ particles. As the content of TiB₂ particles increases, the grain size decreases and the equiaxed grains are closer to the fusion boundary of the scanning track, which are attributed to the increasing nucleation sites and the retarded grain growth during solidification. In addition, the grain coarsening in previous layers is restrained due to the Zener pinning effect. The simulated grain morphology and the predicted influence trend of the TiB₂ content on grain morphology are in good agreement with the experimental observations in the literature.

通过增材制造制造的金属基复合材料部件由于其细晶粒结构和优异的机械性能而受到关注。在本研究中，开发了一种相场 (PF) 模型来模拟 TiB ₂ /316L 不锈钢复合材料在选择性激光熔化 (SLM) 过程中的晶粒演化。增强的TiB ₂颗粒被明确地纳入PF模型，并综合考虑了对晶粒演化的影响，包括诱导的异质成核和对晶界的钉扎效应。模拟结果表明，添加 TiB ₂在扫描轨迹中形成柱状和等轴状颗粒。虽然柱状晶粒是由于从熔池边界外延生长，但 TiB ₂粒子作为熔池内部的成核点，导致等轴晶粒的形成。由于TiB ₂颗粒钉扎晶界，晶界变得复杂。作为 TiB ₂的含量颗粒增大，晶粒尺寸减小，等轴晶粒更接近扫描轨迹的熔合边界，这归因于凝固过程中形核位置的增加和晶粒生长的延迟。此外，由于齐纳钉扎效应，前几层的晶粒粗化受到抑制。模拟的晶粒形貌和预测的 TiB ₂含量对晶粒形貌的影响趋势与文献中的实验观察结果非常吻合。