Effect of α-Al and Si Precipitates on Microstructural Evaluation and Corrosion Behavior of Laser Powder Bed Fusion Printed AlSi10Mg Plates in Seawater Environment

AlSi10Mg is a hypoeutectic alloy that has remarkable characteristics and implemented in diverse areas. Most of the AlSi10Mg parts are fabricated via traditional processes. The AlSi10Mg parts made by these processes have coarser microstructure, reduced mechanical behaviors, and minimum lifespan. This study is aimed at manufacturing the AlSi10Mg parts by Laser Powder Bed Fusion (LPBF) process followed by analyzing their mechanical properties. The microstructure evolution was examined from the micrographs of Optical Microscope (OM), Field Emission Scanning Electron Microscope (FESEM), Electron Backscatter Diffraction (EBSD), and Transmission Electron Microscope (TEM). Tafel, Nyquist, Bode and surface plots were used to determine the corrosion resistance and surface roughness at different intervals. FESEM micrographs revealed the existence of bimodal equiaxed α-Al grains containing Si phase as their grain boundaries. After solidification, the secondary precipitates (Mg₂Si) were segregated in the printed sample which accounts for enhancing the mechanical characteristics. More grain growth and textures were noticed along the building direction of the sample and this direction exhibits higher hardness compared with the scanning direction. Further, TEM analysis confirmed that the formed microstructure is rich in equiaxed α-Al with Si eutectics. Corroded X-ray Diffraction (XRD) plot showed that the maximum intensity of MgAl₂O₄ is observed at 25 h immersion test sample. Among the various samples, 25 h LPBF sample provides significant resistance toward corrosion based on the values of current density, polarization resistance and average surface roughness. This is due to the formation of stable passive film on its surface thereby providing better anti-corrosion characteristics. Graphical abstract: [Figure not available: see fulltext.].