Response to thermal exposure of the mechanically alloyed Al–Ti/C powders

Al–TiC_p composites have been extensively studied in recent years not only because of their attributes as wear-resistant structural materials but also on account of their potential as very efficient grain refiners. Al–Ti–C alloys of various compositions have already been commercialized as grain refining master alloys and have long been in use in aluminium foundries world wide. The present work was undertaken to investigate the possibility of manufacturing Al–TiC_p grain refiner master alloy tablets by the mechanical alloying route. Carbon was mechanically alloyed into Al–Ti alloy powder grains via high energy ball milling. The Al–Ti/C powder blend thus obtained was heat treated to promote the precipitation of TiC. Al₄C₃ was the first phase to form inside the powder grains upon thermal exposure. The Al₄C₃ particles which were too small to be identified with the optical microscope until 750 °C, have grown until 850 °C where they have started to react with Al₃Ti to produce TiC. A very fine dispersion of TiC particles was thus generated inside the powder particles while the Al₃Ti phase has almost vanished.