Aging response affected by the solutionizing time in a 6061 aluminum alloy reinforced with Al2O3 particles

The effect of solutionizing time (ST) at 540 degrees C on the aging characteristics of a composite containing 6061 aluminum alloy matrix reinforced with Al2O3 particles has been compared with 6061 aluminum alloy in its monolithic form (will now be referred to as the alloy). The time required to achieve the peak hardness (TPH) value has been found to decrease from ST of 1.5 to 5 hours while it increases from 5 to 20 hours in a composite containing 0.1 volume fraction of alumina particles (VFAP) at an aging temperature of 200 degrees C. Similar treatment on the alloy, however, shows the opposite behavior. The aging response in the alloy appears to be influenced by the processing of the samples prior to solutionizing (history dependent). The solutionizing of the composite can result in concentration of vacancies and dislocation densities which may be time dependent. The dislocations may be generated from the solutionizing and quenching operation by the coefficient of thermal expansion (CTE) effect and improved bonding between the particle and the matrix. The various proportions of the concentration of Vacancies and dislocation densities appear to control the precipitation sequence in the composite during aging.