Effect of isothermal heat treatment on the creep behaviour of an AlTiCp composite

The microstructure and steady state creep of a powder metallurgy processed Al-20 vol.% TiCp composite have been characterized in as-extruded and in heat-treated conditions (heat treated at 893 K for 24, 96 and 171 h). While as-extruded composite contains only TiC particles, the composite after heat treatment has Al3Ti and Al4C3 particles in addition to TiC. The steady state creep data of the composite show that the creep strength increases substantially after heat treatment. The increase in the creep strength is proportional to the duration of heat treatment up to a certain level and is attributed to the total increase in the volume fraction of particles. The apparent stress exponent and apparent activation energy for steady state creep of the as-extruded composite are very high, 16 and 259 kJ mol−1 respectively, like other aluminium matrix composites. The steady state creep data of heat-treated composite exhibit curvature indicating the possibility of a transition in the creep mechanism. The present results demonstrate that the creep strength of Al-TiC composite can be tailored to suit the requirement by choosing a proper heat treatment. A comparison of the creep strength of various aluminium matrix composites indicates that the Al-TiCp composite after heat treatment has the best creep strength.