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Selective laser-melted (SLMed) 7075 aluminium alloy is prone to cracking. Erbium (Er) could modify the aluminium alloys to prevent cracking in traditional manufacturing processes. In the present study, Er-modified 7075 aluminium alloy powders are prepared to investigate the influence of Er element on crack reduction in SLM. The evolution of Er is characterised by a scanning electron microscope (SEM), a X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The results show that the crack density is reduced with Er addition, but the porosity increases, a new discovery. Based on the SEM and TEM results, Er addition exists in the form of unmelted particles and Al3Er of sub-micrometer scale. The Er particles in the molten pool deteriorate the fluidity and result in higher porosity. The coherency between aluminium matrix and Al3Er favours the grain refinement, therefore the crack reduction.

Laser powder bed fusion (LPBF) is a promising additive manufacturing technique that allows layer-by-layer fabrication of metallic powders. Distinguished thermal dynamics result in the microstructure of intrinsic features. This review aims to provide a thorough insight into the solidification fundamentals and the microstructural tailoring during LPBF. It begins with the introduction of the LPBF and the challenges of its applications with aluminium alloys. The thermal dynamics and its influence on the microstructure in LPBF were thereafter discussed. The attempts to tailor microstructures by refinement in LPBF fabrication of various aluminium alloys were summarised. Finally, the review provides a conclusive remark on the microstructural controlling and an outlook on the remaining challenges and potential research topics in LPBF with Al alloys.