Thermal Expansion of Pressure Infiltrated Aluminum/Hollow Cenosphere Particulate Composites

Abstract

In this article, analytical analyses on the coefficient of thermal expansions (CTE) of pure aluminum alloy containing hollow cenosphere particles were performed by considering particle wall thickness and porosity on the CTE of the composite. The particle wall thickness effect was expressed in terms of the ratio of particle wall thickness and its radius (t/R). A theoretical prediction of the CTE of hollow and solid cenosphere particles was made by using modified rule of mixtures. The average CTE of solid cenosphere particle (7.2 × 10^–6/°C) was much closer to the CTEs of SiC and Al₂O₃ compared to CTE of hollow cenosphere particle. The effective CTE of porosity, calculated using the ROM, was around three times higher than the CTE of pure aluminum and one order higher than the CTE of ceramic particles. The higher effective CTE of porosity suggests the importance of controlling pore content to reduce the CTE of the composites. The pore volume change during thermal cycle was calculated, and the result showed an increase in pore volume after thermal cycle. The CTE increase was discussed in terms of pore volume increase and residual stress.