EFFECT OF DISLOCATIONS ON THE AGING BEHAVIOR OF HIGH VOLUME FRACTION SiC_P/2024Al COMPOSITE

2024 aluminum matrix composite reinforced by SiC particles with 45% volume fraction and 1 μm diameter was successfully fabricated by a squeeze-exhaust casting method. The effect of dislocations on the aging behaviors of SiC_P/2024Al composite was investigated. The results showed that the high-density dislocations in the composite cause the annihilation of quenched-in vacancies, so the GP zone formation is suppressed to some extent. However, the high-density dislocations decrease the thermal diffusion activation energy for the other precipitate formation and accelerate the nucleation of precipitates. Moreover, the high-density dislocations can supply the pathway for pipe diffusion of solute and accelerate the growth of precipitates. So the aging behavior of composite is accelerated and the aging peak of composite appears earlier than that of 2024Al alloy. The high-density dislocations, as preferential nucleation sites for precipitates, bring about the tiny and dense precipitates in the composite.