The size effect of particulate SiC on activation energy for high-strain-rate superplastic flow in powder-metallurgy processed 2124 Al composites

The true activation energies revealed after the incorporation of threshold stress for plastic flow were compared between the two PM superplastic 20%SiCp/2124 Al composites with different reinforcement sizes. There was large discrepancy between the activation energy values. though the volume fraction of SIC was same for the two composites. The composite with the finer reinforcement size (3 mu m) exhibited much larger activation energy value than the other with the relatively coarse SiC particulates (8 mu m). This difference in the true activation energy was attributed to the difference in the SiC/Al interface area per unit volume of composite.