The effect of solid particles on the foaming process of aluminum melt

The effects of in-situ or introduced solid particles on bubble nucleation and stabilization were studied in this paper in the process of producing aluminium foam by direct foaming of the melt. Also analyzed were the state of the solid particles in the aluminium melt and their remaining distribution in the foam block. The results show that the existence of solid particles, which were generated by adding Ca into the aluminum melt and introduced by TiH2 particles as foaming agents, provides the necessary conditions for the heterogeneous nucleation of bubbles. These solid particles can be suspended in the melt and be trapped in the course of bubble nucleation. The solid particles that can't act as nucleating agents may adhere to the generated bubble surface spontaneously and increase its stabilization in the aluminium melt. In the interior of the resulting foam block, these solid particles are mainly concentrated in the foam layer whilst a few of them appear in the bubble-free layer.