Void formation and fracture in a high strength low alloy steel during rapid deformation

Microstructural evaluation of a high strength low alloy steel that is subjected to rapid deformation under high velocity impact is carried out to determine the mechanism of crack initiation and propagation. Prior to crack initiation, the deformation process is dominated by extreme strain localization along shear bands, which occurs as a result of localized adiabatic heating and thermal softening. The susceptibility of the shear bands to micro-cracking and fracture depends on the microstructure of the steel before impact. During deformation, microvoids are initiated inside the shear band. These microvoids subsequently cluster to initiate microcracks which grow along the shear bands leading to fracture. The mechanism, as well as, the microstructural model for the voids' nucleation and growth inside the shear band are presented and discussed. © AES-Advanced Engineering Solutions.