THE CRACKING MECHANISM OF SILICON PARTICLES IN AN A357 ALUMINUM-ALLOY

The cracking of Si particles in an A357 Al alloy has been investigated over a spectrum of stress and strain by varying aging strength and ap plying different tensile strains. The variation of the fraction of bro ken Si particles with stress, strain, and cleavage plane orientation h as been obtained. The features of cracking reveal that cracking of Si particles is a very localized event. A dislocation pileup mechanism is the most probable one among all crack-initiation theories for explain ing the behavior. Based on this mechanism, further deduction has been made to obtain the relationship between the fraction of broken particl es and metallurgical factors. The present data, along with Gurland's a nd that of Low et al., have been found to verify this relationship for the effect of stress, strain, and cleavage plane orientation.