EFFECT OF ISOTHERMAL HEAT-TREATMENT ON THE CREEP-BEHAVIOR OF AN AL-TICP COMPOSITE

The microstructure and steady state creep of a powder metallurgy proce ssed 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 c omposite after heat treatment has Al3Ti and Al4C3 particles in additio n to TiC. The steady state creep data of the composite show that the c reep strength increases substantially after heat treatment. The increa se in the creep strength is proportional to the duration of heat treat ment up to a certain level and is attributed to the total increase in the volume fraction of particles. The apparent stress exponent and app arent activation energy for steady state creep of the as-extruded comp osite are very high, 16 and 259 kJ mol(-1) respectively, like other al uminium matrix composites. The steady state creep data of heat-treated composite exhibit curvature indicating the possibility of a transitio n in the creep mechanism. The present results demonstrate that the cre ep strength of Al-TiC composite can be tailored to suit the requiremen t by choosing a proper heat treatment. A comparison of the creep stren gth of various aluminium matrix composites indicates that the AI-TICp composite after heat treatment has the best creep strength.