Properties and characterization of an aluminium-silicon nitride fibre powder metal composite

In this article, we fabricated one-dimensional 0.5 vol% silicon nitride (Si3N4) fibre reinforced Alunnix123 matrix composites by the powder metallurgy method. Si3N4 is a ceramic material with high strength, stiffness and low coefficient of thermal expansion. The Si3N4 used in the study is comprised of single crystal fibres with sub-micrometre diameter and length < 25 mu m. The size of the fibre is smaller than the metal matrix powder allowing it to coat the metal powder before consolidation rather than forming agglomerations that might lead to pores and poor mechanical properties. We investigated the effects of Si3N4 fibre additions on the densification, hardness, elastic modulus and tensile strength. The experimental results found that the Si3N4 fibre effectively enhanced the mechanical properties of the composites at low additions. The microstructural analysis clearly shows the Si3N4 fibres in the sintered grain boundaries. The interface between the fibre and the Alunnix123 matrix showed good wetting and bonding with only minimal reaction. The Si3N4 fibre reinforced Alunnix123 composites have potential uses in the automobile and aerospace industries due to their improved specific mechanical properties.