Abstract
Herein, a uniform aluminum alloy foam was fabricated by the addition of TiH2 as a blowing agent to Al-6.4 mass % Si in the semi-solid state and subsequent solidification. This was aimed at propounding the stabilization mechanism of the proposed foaming process. The microscopic images, which were the cross section on the center of the foam etched with Weck’s reagent, showed the primary crystals in the semi-solid state and solidifying segregation surrounding the crystals. Thus, it became evident that the area ratio of primary crystals in the semi-solid state approximately equals to the set solid fraction. According to the percolation theory for the cell wall model, the drainage in the cell walls with primary crystals above the percolation threshold was found to be inhibited. By considering that each cell wall is a flow path of the foam, the percentage of the cell walls with inhibited drainage to all the other cell walls was observed to exceed the percolation threshold of the lattice model (0.33) as per the percolation theory. Therefore, it can be concluded that the primary crystals inhibit drainage in some cell walls, ensuring that the stability of the foam is maintained.
Highlights
In recent years, the transportation equipment industry has required lighter and more durable materials to reduce the environmental burden [1]
A three-dimensional assessment and percolation required. In this we examine whether the stabilization mechanism in exact model for percolation theory required
The stabilization mechanism of the aluminum alloy foam was discussed by observing the primary crystals with regard to the percolation theory
Summary
The transportation equipment industry has required lighter and more durable materials to reduce the environmental burden [1]. Metal foam has attracted significant attention in recent years because its lightweight and high shock-absorbing ability render it suitable for the aforementioned requirement. Metal foam has other unique properties such as sound absorption and heat dissipation. These properties are exhibited by the structures of metal foams with closed cells [2]. Fabrication of metal foams via a melt route has commonly been adopted. In this method, gas released from a blowing agent by thermal decomposition forms bubbles in the molten melt. If the pores become coarse by cell wall ruptures, metal foams cannot offer the desired properties
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