Abstract: By the analysis of foam stability mechanism in the gas injection aluminum foaming process, the particle coverage ratio on gas/liquid interface is suggested as the criterion of foam stability for considering the effect of both particle amount and wettability on the foam stability. Critically stable foaming experiments with different particle amount, different particle size and different particle wettability are performed. The criterion is proved to be true by measuring particle coverage ratio on critically stable foam cell wall under different conditions. A model of critical particle coverage ratio on gas/liquid interface is established, and a criterion equation is deduced which contains the volume percentage of ceramic particle, the immersion depth of gas injection nozzle, diameter of particle, critical particle coverage ratio on gas/liquid interface, adsorption coefficient of particles by the bubble and particle wettability. Based on the criterion equation, the product of particle volume percentage and the immersion depth should be greater than a certain critical value for foam stability. This critical value depends on particle diameter, critical gas/liquid interface coverage ratio, adsorption coefficient of particles and wettability. Therefore, this model is useful for selecting the main parameters in foaming process.

Key words: Aluminum foam, Gas injection foaming, Stability