Deformation structures and flow stress in aluminium containing short whiskers

This study reports observations of the effect of a small content (2 vol.%) of SiC whiskers (fibres) on the deformation behaviour at low and medium strains (0.1-10%) of powder-consolidated aluminium. Direct comparisons were made between the material with and without whiskers, and showed that the addition of whiskers did not significantly affect the yield stress, but caused a significant increase in the flow stress and work-hardening rate over the whole of the strain range studied. The yield stress was related to contributions from the thermal residual stress and to dislocations introduced during cooling, and the effects of those two factors were estimated to counterbalance each other. The effect of the whiskers on the flow stress was attributed mainly to a combination of two factors, these being the presence of a mean matrix stress and dislocation strengthening. The relative contributions of these two strengthening components changed with strain. The flow stress of the material at 10% strain could be accounted for reasonably well by linear addition of the various strength contributions.