THE EFFECT OF PARTICLE-SIZE AND VOLUME FRACTION ON THE AGING BEHAVIOROF A LIQUID-PHASE SINTERED SIC ALUMINUM COMPOSITE/

The aging response of a SiC particulate reinforced powder metallurgy a luminum composite was examined as a function of particle size and volu me fraction. The addition of SiC particles ranging in size from 24 to 142 mu m at 9 vol pet had no effect on the aging kinetics of the compo sites. Acceleration of the aging behavior or inhibition of the initial stage of the age-hardening process was observed at 18 and 27 vol pet. The accelerated aging kinetics were consistent with smaller particles creating larger thermal misfit dislocation densities. In addition, it was shown that different combinations of ceramic particle size and vo lume fraction lead to similar effects on the aging behavior. Loss of t he initial hardening response was attributed to the suppression of Gui nier-Preston (GP) zone formation due to the annihilation of excess vac ancies at the thermal misfit dislocations.