Shock induced amorphization as the onset of spall

Spall formation in the glass-forming alloy Cu-Ti was studied via molecular dynamics simulations. It is shown that spall initiation is a combined process where void nucleation is accompanied by local amorphization. The amorphous regions nucleate at the surfaces of the voids at a critical stress and then grow, allowing the voids to grow faster in the mechanically less stable amorphous region. Dislocations are emitted from the amorphous regions and form shear bands between the amorphous regions. Subspall events result in the formation of a damaged layer, including voids, amorphous regions, and shear bands. The simulations are consistent with recent experimental observation of intergranular amorphous bands in shocked boron carbide.