Preparation and characterisation of Al alloys composites discontinuously reinforced by ceramic particles - Development of chemically activated foundry processes and in situ methods

Properties of MMC composites reinforced by ceramic particles depends on the properties of interface particle/metallic matrix. Theoretical studies and researches showed that particles of SiC are more stable in the Al with increased content of Si and Mg. The possible way for the forming of composite is thus the introduction of SiC particles into Al-Si-Mg alloy with later correction of the matrix compositon. Improvement of wetting by chemical activation of surface of particles is one of the most important parameters at foundry method of MMC production, but the processes at the interface are not well known. Reserch showed also an important influence of dissolved hydrogen. The nucleation of micropores with high pressure hydrogen at the interface particle/matrix hinders the benefits of improved wetting. The problems with wetting and hydrogen induced microcraks can be avoided by consolidation of MMC composite from mixture of powders. Hot rolling of Al/SiC powder mixture in Al-container was tested.