Characterization of as-cast microstructure of aluminum foams by melt foaming method

•The anodization treatment can clearly reveal the as-cast microstructure of Al foams.•α-Al grains in cell-walls are much smaller than those in the pore-free layer.•The morphology of α-Al grains is irregular due to the restriction of cell-walls.•The cooling curve of aluminum foams indicates CaAl4 was formed during solidification.