金属增材制造过程中材料微观组织演化的模拟研究

金属增材制造是集设计、制造一体化的一种新型金属构件制造技术, 在航天航空、交通运输、生物医疗等领域具有广阔的应用前景. 金属增材制造材料的力学性能与其材料微观组织密切相关. 因此, 发展金属增材制造过程中材料微观组织的模拟方法, 有助于指导和优化金属增材制造的工艺参数和流程, 从而制备出性能优异的金属材料. 本文发展了基于连续体假设的热传导模型与元胞自动机相结合的模拟方法, 并利用生死单元方法, 考虑晶粒的重熔和再生长过程, 解决了金属增材制造中多层粉末制造的数值模拟问题. 本文采用该方法模拟了镍基合金IN718、不锈钢316L和高熵合金FeCoCrNiMn的增材制造过程, 并获得了这些增材制造合金的典型材料微观组织, 其模拟结果与实验结果相吻合. 同时, 将该方法拓展到三维尺度的模拟, 研究了镍基合金IN718增材制造过程中三维晶粒的形核和生长. 最后, 对金属增材制造过程中材料微观组织演化的模拟研究中的主要问题进行了总结和展望. 

Numerical simulations for microstructure evolution during metal additive manufacturing

As an emerging manufacturing technology, metal additive manufacturing has broad application prospects in aerospace and aeronautics, transportation, and biomedical engineering. The mechanical properties and performances of materials produced through metal additive manufacturing are determined by their microstructures. It is of great importance to develop the numerical simulations for microstructure evolution during metal additive manufacturing. These simulations can guide and optimize the processing (especially the processing parameters), leading to fabricating the metallic materials with excellent properties and performances. Here, we develop a numerical method for metal additive manufacturing that integrates the heat conduction model with the cellular automaton method. This method can be used for the simulations of multilayers powder fabrication in metal additive manufacturing by utilizing the element birth and death technique and by considering both remelting and regrowth processes of grains. We use this method to predict the typical microstructures of nickel-based superalloy IN718, stainless steel 316L, and FeCoCrNiMn high-entropy alloys fabricated through metal additive manufacturing. The predictions from numerical simulations are consistent with the experimental results. Furthermore, we extend this method to simulate the three-dimensional microstructure evolution of nickel-based superalloy IN718 during metal additive manufacturing. Finally, we point out some important issues and challenges for future research on the numerical simulations for the process of metal additive manufacturing.