Influence of the microstructure on the compressive behaviour of porous aluminas: From microstructural characterisation to fracture mechanisms

Abstract

The mechanical response of porous aluminas under compressive loading was studied and compared with the fracture mechanisms. Aluminas with a wide range of pore sizes and porosity rates (1–60%) were produced to deconvolve the effects of pore rate, size and morphology on mechanical response. A transition from brittle to quasi-brittle behaviour appears when the porosity rate reaches 60% and a decrease in mechanical properties as the porosity rate increased. At a porosity rate of 20%, a first alumina was produced with micrometric, interconnected pores, while a second was produced with isolated spherical and mesometric pores. The Young’s modulus is little affected by pore size and morphology, while failure stress decreases with increasing pore size. At iso-density, different grain arrangements lead to different fracture mechanisms despite a similar mechanical response: the more compact the grain arrangement, the more transgranular the crack propagation.