Evolution of foamed aluminum melt at high rate tension: A mechanical model based on atomistic simulations.

Dynamics of foamed metal melt relates to the following problems: cavitations in melt at negative pressure; ablation and nanostructuring of the surface layer of materials under the action of powerful sub picosecond laser pulses; additive manufacturing; and production of solid foamed metals. We propose a mechanical model of the foamed melt evolution at the stage of bubble enlargement—after the completion of their nucleation and before the breaking of the inter-bubble walls. The foamed melt is considered as a system of strongly connected bubbles; their size variations are driven by surface forces. The interconnected system of equations for the second time derivatives of the bubble radii is derived by using the Lagrange formalism. The model is verified by comparison with the molecular dynamic (MD) simulation data for aluminum melt at high-rate uniform tension. An algorithm for searching of individual pores is developed and used to analyze the MD data. The size distribution of pores in the melt at the considered stage of enlargement is found to be close to the normal distribution on a finite interval. Evolution of the foamed melt structure is completely determined by the surface tension. The surface tension makes the largest bubbles growing and all the smaller bubbles collapsing, which leads to rapid reduction of the total number of bubbles. The foamed melt maintains negative pressure determined only by the size distribution of bubbles and the surface tension coefficient. [ABSTRACT FROM AUTHOR]