Phase Field Modeling of Thermal Transport for Predicting and Preventing Porosity and Solidification Cracking in Additive Manufacturing

该项目考虑了航空航天、汽车、海军、石油和能源行业中使用的高端增材制造金属产品的几何精度和机械质量。对高温过程的基本了解，例如激光加热如何与金属粉末相互作用，以及粉末熔化和熔合过程中表面缺陷如何演变，是增材制造成功的关键。通过理论分析和实验验证，本项目的重点是预测和防止包括凝固裂纹在内的表面缺陷的形成。该项目将帮助美国制造业制定战略，以提高增材制造关键金属部件的机械性能。具体而言，该项目将使金属材料供应商，制造机械设计师，产品设计师和最终用户受益。高等教育和多样化的劳动力培训是制造业领域下一代工程师的重点。高强度合金增材制造的主要障碍是几何精度、表面质量和对机械性能的追求。增材制造中的孔隙、缺口和裂纹等缺陷通常由粉末的不完全熔化、界面不稳定性、蒸发和反冲、球化、飞溅和固化期间的开裂引起。因此，迫切需要在粉末和微观结构水平上对工艺动态进行预测建模，以减轻上述机制造成的缺陷。本项目的目标是为此建立一个完整的相场理论框架。该项目包括三项具体任务：（i）通过完全耦合的热、流体、相变和微结构演化模型来解析孔隙度的动态和分布，（ii）将热流体动力学与弹性、塑性、晶粒微结构演化和凝固裂纹的敏感性相结合，（iii）使用NIST增材制造基准测试系列的可用数据进行实验验证和不确定性分析该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project considers the geometry accuracy and mechanical quality of high-end additively manufactured metal products used in aerospace, automobile, naval, petroleum, and energy industries. Basic understanding of the high temperature process such as how laser heating interacts with metallic powders and how surface defects evolve during powder melting and fusion is key to the success of additive manufacturing. Through theoretical analysis and experimental validation, this project focuses on predicting and preventing the formation of surface defects including solidification cracks. The project will help manufacturing industry in the U.S. to develop strategies to increase mechanical performance of critical metallic parts made by additive manufacturing. Specifically, this project will benefit metallic material suppliers, manufacturing machine designers, product designers and end users. Higher education and workforce training with diversity are emphasized for the next generation of engineers in manufacturing field. The primary road block on additive manufacturing of high strength alloys is geometric accuracy, surface quality, and the quest for mechanical performance. Defects such as pores, notches, and cracks in additive manufacturing are often caused by incomplete melting of powders, interfacial instability, evaporating and recoiling, balling, spattering, and cracking during solidification. There is a great need on predictive modeling of the process dynamics at powder and microstructure levels to mitigate defects caused by above mechanisms. The project goal is to establish an integrated phase field theoretical framework for this purpose. The project includes three specific tasks: (i) resolve the dynamics and distribution of porosity by a fully coupled thermal, fluids, phase transition, and microstructure evolution model, (ii) integrate thermal fluid dynamics with elasticity, plasticity, grain microstructure evolution, and susceptibility of solidification cracking, (iii) perform experimental validations and uncertainty analysis using available data from NIST Additive Manufacturing Benchmark Test Series (AM-Bench) ranging from microstructure to thermal mechanical analysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.