Effect of pre-oxidation treatment of TiH₂ and foaming temperature on cell structure of Al-7Si closed-cell aluminum foams

Abstract

A powder metallurgy rapid foaming method was used to prepare Al-7Si closed-cell aluminum foam, and the influence of the preparation process parameters on the expansion rate, porosity, cell number and pore diameter of the aluminum foam after using high thermal conductivity foaming mold was studied. The results show that the TiH2 which is pre-oxidation treated isothermally at 450-500 ℃ for 1 h can refine the particle size, increase the onset decomposition temperature and the peak hydrogen release temperature of TiH2. Excessive pre-oxidation treatment of TiH2 reduces the gas released and expansion rate of aluminum foam. The increase of foaming temperature is beneficial to increase the expansion rate and the number of cells, and has little effect on the porosity and average pore size, but too high temperature can increase the distribution range of low-circularity crack-like cells on the top of the sample. The foaming mold can constrain the direction of expansion and improve the uniformity of the pore size during the cooling process. The powder metallurgy rapid foaming method can obtain aluminum foams with uniform cell structure. The aluminum foams can be obtained with the porosity of 78.1%, the pore diameter of (2.29±0.8) mm and the optimal structure,when TiH2 pretreated at 450 ℃ for 90 min and foaming temperature at 720 ℃ for 160 s.

Keywords

• pre-oxidation treatment of tih₂
• foaming temperature
• powder metallurgy rapid foaming method
• closed-cell aluminum foam