Influence of shielding gas flow on pore evolution in AlSi10Mg/In718 alloy by laser powder bed fusion

Abstract

Laser powder bed fusion (LPBF) manufactured parts often suffer from porosity defects due to the rapid cooling and solidification processes, as well as the complex flow dynamics within the molten pool. These defects directly affect the mechanical properties of the manufactured components. Therefore, it is imperative to investigate control methods for mitigating pore defects and further improve the development of LPBF technology. This work delved into the evolution mechanism of multi pores in LPBF built AlSi10Mg and Inconel 718 alloys. A multi-physics coupled finite element model was developed based on the level-set method, incorporating heat transfer, Marangoni flow, and mass transfer associated with recoil pressure. The results clearly demonstrate that the shielding gas flow has a non-negligible effect on the pore evolution and significantly reduces the porosity in alloys with different dynamic viscosities. The pores are completely eliminated within two alloys as the shielding gas velocity is 2.0 m/s, 3.0 m/s, and 4.0 m/s, respectively. However, the escape time of pores in AlSi10Mg alloys increases dramatically as the velocity is too excessive to over 2.0 m/s, indicating the increase by 92.5 μs and 120.0 μs, respectively, when the velocity reaches 3.0 m/s and 4.0 m/s. The escape time of pores in Inconel 718 is in obvious contrast to that in AlSi10Mg alloy, meaning that the escape time decreases by 5.0 μs at 3.0 m/s and 40.0 μs at 4.0 m/s, respectively. The experimental results show that the shielding gas velocity significantly affects the porosity and mechanical properties of the components.

Keywords

• Laser powder bed fusion
• Shielding gas flow
• Molten pool
• Pore evolution
• Dynamic viscosity