激光增材制造IN 718合金微观结构取向控制的疲劳性能各向异性行为研究

Selective laser melting (SLM) is an additive manufacturing (AM) technique, which has attracted much attention and been extensively developed over the past ten years. However, the crystallographic texture and a complex spatial topological structure with multi-track and multi-layer molten pools are easily introduced into the SLM manufactured components, which are regarded as main reasons for the obvious anisotropy in mechanical properties, especially for anisotropic fatigue properties. In order to clarify this key scientific question, fully-dense IN 718 specimens fabricated by SLM, with specific orientations (<100>//scanning direction，<110>//building direction，<110>//transverse direction ) and two types of distinct textures via different scanning patterns (bidirectional scanning with and without a rotation of 90° between the layers), are selected to investigate the influence of two microstructure orientation parameters (the spatial topological structure with multi-track and multi-layer molten pools and the crystallographic texture) on the anisotropic behavior of mechanical property, respectively. It is expected that models based on various microstructure analysis strategies and theoretical calculations will be proposed to elucidate the role of microstructure orientation in determining the anisotropic mechanical property. The findings and results from the project will provide a theoretical basis on SLM process design and fabrication of structural components with high-fatigue reliability by tuning the microstructure orientation parameters.

作为增材制造技术之一的选区激光熔化技术(SLM)近年来得到了广泛的发展和应用。但SLM技术易在材料中引入多层熔池界面拓扑结构和晶体学织构，从而导致SLM成形材料力学性能，特别是疲劳性能的各向异性。针对这一关键科学问题，本项目拟选取SLM成形的高致密度IN718合金为模型材料，针对熔池界面拓扑结构和晶体学织构两个主要控制参量，设计制备具有特定取向(<100>//扫描方向SD，<110>//打印方向BD，<110>//横向TD)的样品和以两种扫描方式（交叉打印和平行打印）引入的不同晶体学织构样品，分别考察多层多道熔池界面拓扑结构和晶体学织构对IN 718合金疲劳性能各向异性行为的影响规律；结合各种微观结构分析手段和理论计算，建立微观结构取向与合金疲劳性能各向异性间关系的理论模型。项目研究结果将为SLM成形制造工艺设计及高疲劳性能所需的结构控制参量的优化提供理论参考依据。

作为增材制造技术之一的选区激光熔化技术(SLM)近年来得到了广泛的发展和应用。但SLM 技术易在材料中引入多层熔池界面拓扑结构和晶体学织构，从而导致SLM成形材料力学性能， 特别是疲劳性能的各向异性。针对这一关键科学问题，本项目选取了SLM成形的高致密度IN718 合金为模型材料，针对熔池界面拓扑结构和晶体学织构两个主要控制参量，设计制备了具有特定取向(<100>//扫描方向SD，<110>//打印方向BD，<110>//横向TD)的样品和以两种扫描方式(交叉打印和平行打印)引入的不同晶体学织构样品，分别了考察多层多道熔池界面拓扑结构和晶体学织构对IN 718合金疲劳性能各向异性行为的影响规律；阐明了扫描方式对组织结构演化行为的影响规律；通过调控扫描方式，可以在不显著降低合金拉伸塑性的情况下，有效提升合金的室温拉伸强度和疲劳强度。通过对比三种热处理态合金样品发现，均匀化+时效态合金表现出最佳的强塑性能匹配以及更高的疲劳极限，其疲劳极限相较其余两类样品进一步提高了约10%。结合各种微观结构分析手段和理论计算，建立了微观结构取向与合金疲劳性能各向异性间关系的理论模型。项目研究结果不仅为通过调控扫描方式，实现增材制造合金零部件特定位置的组织结构和力学性能设计提供了理论指导，且为后续通过热处理调控组织结构，制备高疲劳可靠性的SLM成形合金以及制定针对SLM成形Inconel 718合金的标准热处理制度提供了理论指导。