Electron back-scatter diffraction study of inoculation of Al

The microstructure of cast commercial-purity aluminium inoculated by addition of an AI-TI-C grain refiner has been studied by scanning electron microscopy and electron back-scatter diffraction (EBSD). It is found that a small fraction of the TiC particles present in the melt act as nucleation centres for grains. EBSD shows that the aluminium grains have a crystallographic cube-cube orientation relationship with the particles on which they nucleate. Nucleation occurs only on the largest particles, consistent with model predictions. Despite potential thermodynamic instability, TiC particles are effective nucleating agents.