EFFECT OF DELTA-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 di fferential scanning calorimetry (DSC) technique, microhardness tests, and transmission electron microscopy (TEM) observation. Composites fab ricated with the 2024 alloy matrix were infiltrated through a ceramic preform using a squeeze-casting process. The alumina fibers had a cons iderable effect on the aging response of the matrix alloy in composite s. Alumina fibers caused suppression of Guinier-Preston (GP) zone form ation in composite that reduced the peak hardening during artificial a ging. The suppression of GP zone formation in composites is believed t o be due to the fiber-matrix interface, which acts as a sink for vacan cies during quenching. Moreover, the presence of reinforcement does no t alter the kinetics of the subsequent artificial aging of these Al2O3 /2024Al composites.