A Micromechanical Mechanism of Fracture Initiation in Discontinuously Reinforced Metal–Matrix Composite

Fracture initiation by cracking of silicon particles during plastic deformation has been studied for the Al–17wt.% Si-nucleated alloy. The number of cracked particles increases with the applied strain. The larger and longer particles are more prone to cracking. In coarser structures, particle cracking occurs at low strains, while in more homogeous structures the progression of damage is more gradual. The variation of the fraction of broken silicon particles with stress, strain, and cleavage plane orientation has been obtained. The features of cracking reveal that cracking of silicon particles is a very localized event. A dislocation pile up mechanism is the most probable one among all crack initiation theories for explaining the behavior. A relationship between the fraction of broken particles and metallurgical factors was found.