Influence of self-repair mechanism of internal oxide film on the preparation of aluminum foam fabricated using a non-thickening foaming process

Aluminum foam, as a typical multifunctional porous metal material, has demonstrated significant potential for application in modern industries. However, the addition of stabilizers to enhance foaming stability resulted in a brittle failure mode of aluminum foam, which limited its practical applications. Therefore, this paper improved the non-thickening foaming technology for fabricating closed-cell aluminum foam, where a slight amount of CaCO3 served as an internal oxide film self-repair agent was introduced into the foaming mixtures. The addition of CaCO3 caused a shift in the temperature at which the 1st endothermic peak was observed, from 522.8 °C to 576.9 °C, and contributed to the occurrence of an exothermic reaction within a temperature range of 670 °C–690 °C. The gradual release of CO2 altered the composition of oxidizing gas within the enclosed bubbles, leading to the self-repair of the ruptured oxide film caused by the growth of bubbles. Consequently, the microtopography of the bubble surface was modified. However, the excessive CaCO3 led to the deterioration of pore structures and an increased bubble-free layer. The results of the three-point bending test indicated that sample fabricated using 0.3 g CaCO3 exhibited excellent load-bearing capacity, with an approximate enhancement of 60.4 % in bending capacity observed under the same deflection of 10 mm. The predominant failure mode of non-thickened aluminum foam was characterized by ductile fracture.