Response to thermal exposure of Al/K 2TiF 6/C powder blends

Abstract

Al–TiC p composites have been extensively studied in recent years owing to their attributes as wear-resistant structural materials and to their potential as efficient grain refiners. In the present work, Al–TiC p composites were synthesized in situ by the powder metallurgy route, by heat treating Al/K 2TiF 6/graphite powder blends without the benefit of mechanical milling/alloying. TiC particles formed in aluminium after a series of reactions when Al/K 2TiF 6/C powder blend was heated at 1000 °C. First, the K 2TiF 6 salt was reduced by aluminium at approximately 560 °C generating Al 3Ti particles and K–Al–F salts which make up additional consitutents in the powder blend. Further increase in the temperature led to the melting of the aluminium powder which wet and engulfed the Al 3Ti particles thus produced. K–Al–F salts are believed to have played a key role in the sintering process by cleaning and stripping the surface oxides of the aluminium powders. The Al 3Ti particles were gradually replaced by TiC particles when the powder blend was heated above 800 °C. One-hour heating at 1000 °C yielded a composite sample with predominantly TiC particles.