Investigation Of The Physical Properties Of Open-cell Aluminum Foams

The unique structure of aluminum foams endow them with great potential applications in mechanical engineers and high technology for decades. In this paper open-cell aluminum foams samples with basically controllable pore structure and uniform distributed pore were prepared by infiltrating process. Properties of electrical conductivity, thermal conductivity and thermal expansion were investigated. At same time, we also have studied the thermal conductivity of the aluminum matrix composites.Firstly, the open-cell aluminum foams have been produced by pressure infiltrating process, and the structural parameters such as cell size and porosity of the aluminum foams were controlled by adjusting process parameter. The electrical conductivity of the aluminum foams of different parameters was measured by the "four point"method to investigate their relationship with the relative density and pore size of the foams. The results show that the electrical conductivity of the aluminum foams increases with increasing in their relative density, and the power law function can be successfully applied to describe the dependence of electrical conductivity of foams. For the aluminum foams with a roughly same relative density, more defects were created in the foam of smaller pore size, and a lower electrical conductivity is obtained, compared with that of larger pore size.Secondly, the thermal conductivity of aluminum foams has been measured as a function of cell size and relative density. The results show that the thermal conductivity of foam rapidly decreases with the increase of porosity or the decrease of relative density, and the percolation theory can be successfully applied to describe the dependence of the thermal conductivity of aluminum foams on the relative density. The cell diameter has a minor influence on the thermal conductivity of foam and appears to have a negligible effect.On the base of the thermal conductivity of the open-cell aluminum foams, we also have studied the thermal conductivity of the aluminum matrix composites. At the graphite at the 50 percent, the Gr/Al composites possess relatively excellent thermal properties, and the thermal conductivities of Gr/Al matrix composites are larger than pure aluminum but smaller than graphite. The power law function canbe successfully applied to describe the dependence of electrical conductivity of foams. The thermal conductivity of Gr/Al composites decrease with the increase of Gr additions to the matrix, but the influence of cell diameter (>0.3mm) on this property is almost negligible.Lastly, thermal expansion coefficient of the open-cell aluminum foams was tested using PCY ultra-temperature horizontal dilatometer. The important geometric parameter that affects the properties of foams, such as cell diameter and relative density, has been examined. Both cell diameter and relative density on this property are almost negligible and the results were compared with a model of Gibson.