激光时序调制下增材制造镍基合金熔池动态凝固机制与组织调控研究

近年来开发的激光时序调制工艺有望解决传统连续激光增材制造镍基高温合金存在的组织生长与脆性相控制难题，但该工艺下熔池复杂热物过程及动态凝固机制尚不清楚，这极大限制了该工艺的发展与应用。针对上述问题，本项目拟采用数值模拟与实验研究相结合的方法，开展激光时序调制下熔池热质传输规律与动态凝固机制研究。通过建立熔池三维瞬态数学模型，结合熔池实验监测，研究激光时序调制下熔池动态特征与热质传输规律；通过系统的微观结构表征及力学性能分析，结合凝固理论，研究激光调制参数对组织及性能的影响规律及机理。本项目旨在阐明激光时序调制下熔池凝固条件的动态演变规律，揭示凝固条件的动态波动对显微组织的影响机理，建立工艺-熔池行为-组织-性能之间的映射关系，实现对熔池凝固过程与成形件组织及性能的主动调控。项目研究成果将拓展现有非平衡金属快速凝固理论，为成形件组织及性能的主动调控提供新的技术途径。

In recent years, laser modulation technique is expected to control the solidification structure and brittle phase in traditional continuous-wave laser additive manufacturing of nickel-based superalloys. However, the thermal-physical process and the dynamic solidification mechanism of the molten pool under laser modulation are still unclear, which greatly limits the development and application of this process. This project intends to investigate the heat and mass transfer law and the dynamic solidification mechanism of the molten pool under the laser modulation using the combined numerical simulation and experiment approach. In this project, the dynamic features and the heat and mass transfer behaviors of the molten pool are investigated by establishing a three-dimensional transient mathematical model, combined with the experimental monitoring of the molten pool. The effects of laser modulation parameters on solidification microstructures and mechanical properties of the parts are studied by the systematic characterization of microstructure and the test of mechanical property, combined with the analysis of solidification theory. This project aims to clarify the dynamic fluctuation laws of solidification conditions under laser spatial-temporal modulation and to reveal the influence mechanism of the dynamic fluctuation of solidification conditions on the microstructure and property. The relationship among process parameter, molten-pool behavior, microstructure and mechanical property will be established. The active control of the molten-pool solidification process and the microstructure of the fabricated part will be realized. This project not only enriches the existing non-equilibrium rapid solidification theory of metals, but also provides a new technical approach for the control of solidification structure and mechanical properties of the fabricated part.