Effect of instability of TiC particles on grain refinement of Al and Al-Mgalloys by addition of Al-Ti-C inoculants

Thermodynamic modelling shows that while TiC is a stable phase in AI-TI-C g rain refiners, it should decompose on addition of the refiners to typical A l alloys. The present work assesses the impact of melt composition on TiC s tability anti on grain refiner performance, which has been tested at variou s addition levels in Al and Al - Mg alloys. In melts with compositions that stabilise TiC, there is effective grain refinement with little fading of p erformance on holding the refiner in the melt. In melts with compositions i n which TIC is not stable, grain refinement is impaired even at short holdi ng times, and becomes markedly worse at longer holding times. It is conclud ed that in typical cases progressive decomposition of TiC does occur, and t hat this can have a significant effect on grain refinement by inoculation w ith Al-Ti-C master alloys.