ACCELERATED AGING PROCESSES IN CERAMIC REINFORCED AA-6061 COMPOSITES

An accelerated aging response, detected in AA 6061 based metal matrix composites, in age hardening curves was examined via microstructural observations. The influence of vacancies on the precipitation processes of AA 6061 alloy and its composites was also considered. In the composites, after peak aging, a higher density of dislocations and a higher density of intermediate beta' precipitates was observed. It is thought that the dislocation assisted nucleation processes reduce the apparent activation energy for precipitation, and a higher nucleation density of precipitates in the composites, compared with that in the AA 6061 alloy, leads to an earlier attainment of the peak aging condition.