Linking printing layer thickness to performance-critical microstructure and corrosion in LPBF AlSi7Mg

Unlocking the potential of laser powder bed fusion (LPBF) AlSi7Mg for high-performance applications hinges on a deep understanding of its microstructural response to processing parameters. Previous studies investigating the layer thickness influence on LPBF AlSi7Mg have primarily focused on thicker printing layers (30 μm–100 μm), which neglects the potential impact of very thin layers (e.g., 20–30 μm) on the microstructure and overall properties like service stability. This study aims to fill this knowledge gap by systematically examining the effect of printing layer thickness within this thin critical range on the microstructural evolution and subsequent corrosion behavior of LPBF AlSi7Mg (after T6 heat treatment). Our results demonstrated that the 30 μm printing thickness condition consistently exhibited superior microhardness and corrosion resistance. The detailed microstructural and phase formation analysis revealed that layer thickness has a direct impact on cooling rate and resultant element distribution, which can induce the formation of different Fe-bearing phases like π-AlFeMgSi and β-AlFeSi. Along with different phase formations, the grain boundary (GB) and Si-rich phase concentration and distribution significantly influenced performance by disturbing the passivation layer, which provides valuable insights for optimizing LPBF processing parameters, enhancing the reliability of AlSi7Mg components, and advancing the understanding of this critical material for demanding applications.