Influence of particle additions on the foaming behaviour of AlSi11/TiH2 composites made by semi-solid processing

The influence of Al2O3 and SiC particles on the foaming behaviour of thixocast AlSi11 precursor material was investigated using mechanical and X-ray expandometry, image analysis of X-ray images and optical analysis of metallographic sections. A significant improvement of maximum expansion, collapse behaviour and pore structure could be obtained by addition of 1–5 wt.% particles, with higher efficiency of smaller particles. The role of the particles and the observed variations of efficiency are explained by differences in the way of particle agglomeration on or near cell wall surfaces.