| Summary: | This study focuses on the generation of the bubble-free layer during the fabrication of the metal foam using the direct melt foaming method. The theoretical models for the three stages during the foaming process have been established, and the boundary conditions have been discussed. The results from the theoretical study indicated that the bubble number of the liquid foam played a critical role in the generation of the bubble-free layer, thus, improving the bubble number retards the velocity of the bubble-free layer generation. The liquid film rupture led to the expansion of the local cross-sectional area of the Plateau border channel and increased the drainage velocity, thus, resulting in an enhancement in the bubble-free layer. Additionally, the verification experiments were conducted by employing the graphene nanoflakes (GNFs) as the heterogeneous nucleation agent. The findings indicated that the generation of the bubble-free layer was hindered, and the bubble-free layer was altogether absent in case the content of the heterogeneous nucleation agent was enhanced.
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