International journal of cast metals research vol:22 issue:1-4 pages:70-73
International Conference on Advances in Solidification Process edition:2 location:Graz, Austria date:17-20 June, 2008
During directional solidification of a near-eutectic Al-Mn-Si alloy the univariant eutectic is formed, following the reaction: L ->alpha Al+alpha(AlMnSi)+L' and reveals a non-faceted alpha-Al/faceted alpha(AlMnSi) structure. The addition of titanium diboride (TiB2) promotes the nucleation of intermetallic alpha(AlMnSi) silicide phase at solid/liquid interface as particles, which are pushed and periodically engulfed by the advancing planar interface. This type of growth, called symbiotic growth, leads to a layered microstructure. To study the influence of TiB2 upon the morphology of alpha(AlMnSi) phase various amounts (from 0.05 up to 2.00 wt-%) of TiB2 were added to alloys with identical composition. The results show that the behaviour and the influence of the inoculant is not trivial. Both the presence of titanium diboride at the solid/liquid interface and its inoculation effect determine the final morphology of the silicide phase.