Abstract
In-situ SEM observations of fracture processes in two 6061Al alloy composites reinforced with coarse and fine SiC particles, respectively, were carried out to clarify their fracture mechanisms. It was found that in the coarse particle reinforced composite, voids were formed in the matrix around SiC particles ahead of the main crack tip, then coalesced with each other, and finally connected with the main crack tip, causing propagation of the main crack. However, in the fine particle reinforced composite, multiple micro-cracks were formed at the boundaries between SiC particle clusters and surrounding matrix or within the clusters, then connected with each other, and finally joined with the main crack tip, leading to crack branching and growth of the main crack. Crack branching, multiple cracking and crack deflection were proposed to contribute to the enhanced fracture toughness in the fine particle reinforced composite compared with the coarse particle reinforced composite.
