Effect of δ alumina fibers on the aging characteristics of 2024-based metal-matrix composites

The age-hardening precipitation reaction in aluminum matrix composites reinforced with discontinuous alumina fibers was studied using the differential scanning calorimetry (DSC) technique, microhardness tests, and transmission electron microscopy (TEM) observation. Composites fabricated with the 2024 alloy matrix were infiltrated through a ceramic preform using a squeeze-casting process. The alumina fibers had a considerable effect on the aging response of the matrix alloy in composites. Alumina fibers caused suppression of Guinier—Preston (GP) zone formation in composite that reduced the peak hardening during artificial aging. The suppression of GP zone formation in composites is believed to be due to the fiber-matrix interface, which acts as a sink for vacancies during quenching. Moreover, the presence of reinforcement does not alter the kinetics of the subsequent artificial aging of these Al₂O₃/2024Al composites.