Modeling the Age-Hardening Behavior of SiC/Al Metal Matrix Composites

A model for the age-hardening behavior of SiC/Al metal matrix composites has been developed to describe the variation of the yield strength with aging time. The model incorporates the heterogeneous nucleation and growth of the precipitates along the dislocations to describe the accelerated aging behavior. It has been shown that the size and volume fraction of the SiC particles as well as aging temperature influence the age-hardening behavior. Increasing the aging temperature accelerates the aging process by increasing the velocities of the total nucleation rate (the sum of the nucleation per unit time) and growth of the precipitates due to the enhanced diffusion velocity of the solute atoms. Decreasing the size and increasing the volume fraction of the SiC particles also accelerate the aging process by enhancing the total nucleation rate due to the increased dislocation density. It was found that the yield strengths have been well predicted by the model for both SiC-reinforced Al-Cu-Mg alloy and Al-Mg-Si alloy, which have plate-shaped and needle-shaped precipitates, respectively.