异种金属在激光熔覆、焊接等热加工成型过程中易出现偏析带，偏析带常与凝固裂纹伴生，直接影响加工成型后的力学性能。为了研究异种金属材料在冶金结合时偏析带形成机制及其演化规律，本工作将元胞自动机方法和Eulerian多相流算法相结合，建立了在316L不锈钢上激光熔覆IN718合金的二维熔化凝固模型，系统研究了激光熔覆过程中的温度场、熔池形貌、熔体流动以及元素分布的演化过程。通过对比熔池几何尺寸和晶粒取向验证了模型的合理性，对比x方向和y方向上的Fe元素含量分布来验证模型的可靠性。模拟结果表明，316L不锈钢基板上激光熔覆IN718合金冶金结合过程中出现了Fe、Ni元素富集、贫瘠交替分布的偏析带，与实验结果吻合较好。通过分析熔池中Fe元素的分布、熔池形貌和熔体流态的演化过程，该偏析带是熔池凝固过程中流体流动与熔池形貌变化不协调的结果。

During laser cladding, welding, and other hot forming processes, dissimilar metals can form segregation bands. These bands often lead to solidification cracks that can directly affect the mechanical properties of the processed and formed materials. To study the formation mechanism and evolution of segregation bands during metallurgical bonding of dissimilar metal materials, a two-dimensional melting and solidification model for laser cladding of IN718 on 316L stainless steel was used. This model was established using the cellular automata method and Eulerian multiphase flow algorithm. The evolution of the temperature field, molten pool morphology, melt flow, and element distributions during laser cladding was comprehensively analyzed. The rationality of the model was confirmed by comparing the melt pool geometry and grain orientation. Additionally, the reliability of the model was confirmed by comparing the distribution of Fe element content in the x- and y-directions. The simulation results reveal that during the metallurgical bonding process of laser cladding IN718 alloy on the 316L stainless steel substrate, distinct segregation zones are observed, which are characterized by the enrichment of Fe and Ni elements and an unideal alternating distribution pattern. This finding is in high consistency with the experimental results. The Marangoni force drives more Fe elements from the bottom of the melt pool (substrate) to the rear end of the melt pool, increasing the temperature of the liquidus at that location. This solidification promotion at the rear end of the melt pool causes actual solidification liquidus temperature(T_a) to be biased toward substrate liquidus temperature(T_b), resulting in the formation of a region with a high concentration of Fe elements. The rear end of the melt pool takes on a “bulging” shape, increasing the melt flow rate within the pool. This increase rolls more Fe elements from the front end of the melt pool (powder) to the rear end of the pool. Consequently, the liquidus temperature at the rear end of the melt pool decreases, biasing T_a toward the liquidus temperature of the powder(T_p). This process hinders solidification at the rear end of the melt pool, resulting in the formation of a region with a reduced concentration of Fe elements. The rear end of the melt pool flattens gradually, decreasing the melt flow rate and drawing more elements from the front to the rear end. This change results in the formation of a segregation zone with an alternating distribution of high and low Fe element content, which is consistent with the experimental results. Through the analysis of the distribution of Fe elements in the melt pool, the morphology of the melt pool and the evolution of the melt flow state, it is evident that this segregation zone arises from the mismatch between fluid flow dynamics and the morphological changes of the melt pool during the solidification process. The rate at which the solid-liquid interface moves can be calculated by finding the difference in the solute concentration between the interface neighboring cells. Fluctuations in the molten pool flow cause the morphology of the rear end of the molten pool to constantly change, resulting in varying concentrations of Fe element after solidification. Therefore, increasing the homogeneity of element mixing in the molten pool can reduce the degree of segregation. During the experimental process, appropriate increase in the laser power and scanning rate reduction can improve the quality of the cladding layer.