Influence of shielding gas on melt-pool solidification in AlSi10Mg/ Inconel 718 alloys by laser powder bed fusion

The correlation between melt-pool solidification and cooling rate in the laser powder bed fusion (LPBF) process is essential for optimizing parameters to achieve the desired mechanical properties of manufactured parts. In this study, we investigated the effect of the shielding gas (SG) velocity on the solidification and microstructure of AlSi10Mg and Inconel 718 melt pools during LPBF additive manufacturing. A multi-physics finite element model was used to simulate the melt pool evolution, which was validated by in situ temperature monitoring. The results demonstrate that increasing the SG velocity intensifies convective heat transfer, which in turn modulates the Marangoni flow and surface tension gradients. A pivotal discovery lies in the material-specific sensitivity to SG dynamics: For Inconel 718, an optimal processing window was identified at 2.0 m/s, where stabilized fluid dynamics effectively mitigated residual stress and defect proliferation. More interestingly, for AlSi10Mg, high SG velocity (4.0 m/s) triggered dynamic recrystallization via localized thermal-stress coupling. This mechanism facilitated significant grain refinement, yielding superior synergy between strength and ductility. These findings reveal a novel correlation between atmospheric flow regulation and microstructural engineering, thereby offering a new paradigm for optimizing LPBF parts.