Interface characterization, precipitate evolution, and quantitative modeling of the microstructure/strength relationship in SiCp/2024Al composite

In this research work, 35vol% SiC particle-reinforced 2024 aluminum alloy matrix composite was prepared by a powder metallurgy method. The interface microstructure and effect of different aging treatments on the precipitate evolution were investigated. A comprehensive quantitative model that considered the synergistic effects caused by different strengthening mechanisms has been estimated to predict the yield strength of the composite. The description of the precipitate evolution has been introduced into this model, including type, size, and volume fraction, which correlate with the strengthening response in the hot-pressed and aged composite. The results indicate that the SiC/Al interface is clean and semi-coherent. The precipitated phases are coarse micron intermetallic particles in the hot-pressed composites, while they change to nanosized plate or rod-shaped particles after aging treatments. With the increase in aging time from 20min to 40h at 190 degrees C, the size of the precipitate increases, while the quantity of the precipitate first increases and then decreases. The relationship between precipitate and Al matrix interfaces first is coherent, and then semi-coherent and incoherent in the end. Quantitative model based on the aging kinetics can accurately describe the growth of precipitates, and the comprehensive quantitative yield strength model predictions broadly agree with the experimental data for both hot-pressed composites and aged composites.