静磁场下IN718合金SLM微熔池凝固组织演变及强韧化机制研究

随着选区激光熔化（selected laser melt, SLM）成型工艺在航空航天和高端装备制造领域的快速推广应用，基于拓扑结构设计并具备复杂形状的高性能镍基高温合金SLM零件需求日益增加。目前由于缺乏对微小熔池的凝固过程的控制和缺陷产生机理的研究，使“缺陷、变形与尺寸超差”成为制约金属构件SLM成形技术发展和应用的三大难题。本项目选择大量用于航空发动机热端部件的IN718合金为研究对象，通过外加静磁场对SLM熔池流动进行主动控制，定量化描述静磁场条件下熔池在超高温度梯度和强约束下的凝固行为，研究静磁场作用下微熔池内多尺度热电磁效应及凝固组织演变规律，揭示静磁场下SLM成形的孔隙形成机理与抑制手段；构建“熔道表面形貌-孔隙-微观组织”的相关性，揭示静磁场作用下SLM合金强韧化机制，为SLM及其他激光增材成型零件的可控制备提供理论依据。

With the rapid promotion and application of selective laser melting (SLM) in aerospace and high-end equipment manufacturing; the demand for nickel-based superalloy SLM parts with complex shape based on topological structure design is increasing. Due to the lack of understanding of solidification process and effective research on the mechanism. Defects, deformation, defects, and size tolerance have become three major problems in the development and application of SLM forming technology. In this project, IN718 SLM parts used for hot end parts of aero-engine is selected as the research object, the external static magnetic field is applied to the SLM molten pool to study the solidification behavior of the molten pool under the condition of ultra-high temperature gradient and strong constraint quantitatively. The multi-scale thermoelectric magnetic effects and solidification structure evolution rule in the molten pool under the effect of static magnetic field are studied, the mechanism and contorl method of porosity in SLM under the static magnetic field will be studied. The research results will show that the strength and toughening mechanism of SLM alloy with the assistance of static magnetic field, which also provides a theoretical basis for the controllable preparation of SLM and other laser fabricated parts.