Additive Manufacturing of Al-12Si Alloy by Powder Laser Bed Fusion: an Investigation into its Microstructural Processes Formation and its Effects on Mechanical Behavior

Additive manufacturing (AM) has evolved as an innovative approach to building 3D objects by addition of layer-upon-layer of material, which has brought some added industrial benefits from the microstructural processes and mechanical behavior aspects. In the current study, Al-12Si (wt.%) alloy has been fabricated based on AM utilizing the laser powder bed fusion (L-PBF) technique. Its mechanical behavior and microstructural processes formation were investigated and compared to those of a cast alloy with a similar elemental composition. It was observed that the former alloy exhibits a hierarchical microstructure consisted of cellular sub-structures (~ 600 nm), melt pool, and grain boundaries which is outstandingly different from that of cast alloy. The cast form of this alloy exhibit a needle-like eutectic Si structure. However, L-PBF processed of the same alloy shows a finely dispersed phase of Si. This difference in microstructure substantially affect the mechanical properties (elastic-plastic behaviour) of the material. Based upon indentation examination (hardness testing), the nanohardness of the L-PBF fabricated alloy (1.3 – 1.09 GPa) was found to be about 1.85 times higher than that of the cast alloy (0.62 GPa). Furthermore, a remarkable improvement in shear strength of the L-PBF processed alloy, between 0.40 -0.41 GPa, was achieved in comparison to that 0.32 GPa of the cast alloy.