Abstract: Closed-cell aluminum foam with different amounts of Mg and carbon fiber were prepared by the method of molten body transitional foaming process， and the effect of Mg element on foaming process and pore structure of aluminum foams was discussed. The main results are as follows: when the addition of Mg element increases， the expansion rate of foam increases significantly and the range of the pore size distribution becomes broader， associated with the increasing number of small stomata. The microstructures of the inner and surface of the pore wall show that the pore wall can be smoother， thinner and more stable after adding Mg， because the surface tension of molten aluminum is reduced， the wettability between aluminum and oxide particles is improved and the gas release during the foaming process increases. As a result of Mg addition， it is achieved that the porosity of aluminum foam can be more than 90%.

Key words: aluminum foam, Mg, expansion rate, distribution of pore size, stability of pore wall