A review on the correlation between microstructure, heat treatment and mechanical properties of additively manufactured AlSi10Mg by LPBF

Out of three additive manufacturing (AM) process categories for metallic materials viz., direct energy deposition (DED), powder bed fusion (PBF), and sheet lamination, PBF offers advantages in fabrication of complex geometries, reducing material waste, and creation of customized components with unparalleled design freedom. Focus of this article will be on laser-PBF (LPBF), which can produce parts with high resolution, good surface finish, and has larger range of material options compared to other AM processes. Eutectic and near-eutectic Al-Si alloys are the most suitable materials for AM due to their narrow solidification range, lower thermal expansion, and high melt pool flowability which results in low shrinkage and lower susceptibility to hot cracking. AlSi10Mg is widely used for AM and as-built LPBF AlSi10Mg exhibits cellular microstructure with Al-Si eutectic at the cell boundaries. Mechanical properties like tensile strength, ductility, and fatigue strength, of LPBF AlSi10Mg depend on its processing conditions viz., laser power, powder layer thickness, hatch spacing, and post-processing conditions like heat treatment cycle, shot peening, and other surface treatments. Both processing and post-processing conditions, affects the microstructure, which in turn is correlated with the mechanical properties. Unique microstructure of the as-built LPBF AlSi10Mg is due to rapid solidification conditions and explains the improved mechanical properties compared to as-cast counterpart. But proper post processing is required to remove residual stresses developed during processing. Heat treatment cycles used for conventionally produced aluminum alloys through casting attaining final tempers of T6, T7, T4, etc., as per ASTM B917 destroys the unique microstructural characteristics of LPBF AlSi10Mg and its associated advantages and there is a need for developing tailored heat treatment cycles for LPBF parts. The present work attempts to develop a comprehensive understanding of effect of processing conditions, heat treatments on the microstructure, and mechanical properties of AlSi10Mg produced through LPBF.