A microscopic model for the thermal conductivity of a porous 380-aluminium alloy
Alejandro Ramírez, Francisco Beltran, J Yañez-Limón, Yuri Vorobiev, Jesús González-Hernández
The effective values of thermal diffusivity, specific heat, and thermal conductivity of a porous 380-aluminium alloy were investigated as a function of the volume percentage of porosity in the range 0% – 10.35%. The samples of the alloy were prepared by melting in a gas-fired furnace. The sample characterisation was carried out by means of differential calorimetry, photoacoustics, density measurements, and a computer image analysis. The thermal conductivity obtained on samples with the low degree of porosity is in good agreement with the data published for the solid 380-aluminium alloy. The measured thermal diffusivity of the porous samples shows only a weak dependence on porosity, whereas the thermal conductivity and the specific heat have an approximately linear decrease with the increase in the amount of porosity. To explain the experimental results, the existing phenomenological models were analysed; in addition, a new microscopic approach is proposed which takes into account the features of the motion of the electrons and phonons in a porous media. The microscopic model fits the experimental results well.