激光立体成形中熔池凝固微观组织的元胞自动机模拟∗

摘要

A two-dimensional multiscale model is presented for simulating laser melting process, which is the same as laser solid forming (LSF) without the addition of metallic powders into the molten pool. The metallurgical process in molten pool is simulated, including the temperature distribution, the pool shape, and the solidification microstructure. The shape of the molten pool and the microstructure in Fe-C single crystal substrate at a laser scanning speed of 15 mm/s is simulated. Results reveal the instability from planar interface to celldendrite morphologies in the molten pool. At the bottom of the molten pool, the growth morphology is planar interface, which is also called bonding zone. Epitaxial dendrite arrays can be seen to grow above the bonding zone.%本文通过采用自适应网格技术,将激光立体成形的宏观温度场模型和凝固微观组织的低网格各向异性元胞自动机模型(cellular automaton, CA)结合,建立了适用于激光立体成形的集成数值模型。模型包括基材的温度场分布,熔池形貌和熔凝过程的凝固微观组织。模拟了激光扫描速度为15 mm/s时,激光作用在Fe-C单晶基材上形成熔池的形状以及熔池内凝固微观组织。计算结果揭示了熔池内固液界面从平界面失稳到胞枝晶的非稳态凝固过程,并得到了平界面组织形成的白亮带。白亮带上方形成了外延生长的枝晶列。