Investigation by 3D nano-holotomography of the self-healability of an Aluminium alloy produced by additive manufacturing

Al parts might be subjected to overloads leading to voids, cracks and the replacement of the part. A promising solution is to use self-healing material. A self-healing Al alloy was produced by SLM based on Al-Si and Mg powder. The microstructure is composed of a Si network and Mg2Si precipitates in a α-Al matrix. During an overload, void nucleation occurs due to fracture of the Si network and of precipitates. The idea is to use a heat treatment to trigger the diffusion of the healing agents to the cavities. The healing potential of fractured Mg2Si was already proven but the SLM microstructure is different and its influence on the healing efficiency and kinetics needs to be investigated. Nanoholotomography allows observing the same area before and after healing in order to track the damage and to assess the healing potential of the material. As the SLM microstructure will not be noticeable, FIB-SEM will be used to evidence the influence of the microstructure on the healing efficiency.

铝合金构件可能承受过载载荷，进而产生孔隙与裂纹，最终需更换该构件。采用自修复材料（self-healing material）是极具前景的解决方案。本研究基于铝硅（Al-Si）与镁（Mg）粉末，通过选择性激光熔化（Selective Laser Melting，SLM）制备了自修复铝合金。该材料的显微组织（microstructure）由α-Al基体（α-Al matrix）中的硅网络与Mg₂Si析出相构成。当承受过载载荷时，硅网络与析出相发生断裂，进而引发孔隙形核。本研究的思路是通过热处理触发修复剂向孔隙缺陷处扩散。断裂态Mg₂Si的修复潜力已得到证实，但选择性激光熔化制备的显微组织存在特殊性，其对修复效率与修复动力学的影响仍有待研究。纳米全息层析成像（nanoholotomography）可实现同一区域在修复前后的观测，从而实现损伤追踪与材料修复潜力的评估。由于选择性激光熔化制备的显微组织特征难以直接辨识，将采用聚焦离子束扫描电镜（Focused Ion Beam-Scanning Electron Microscopy，FIB-SEM）来阐明显微组织对修复效率的影响。