Formation of Adiabatic Shear Bands in a Tempered Steel under Dynamic Loading and their Damage Effects

Abstract

Abstract In this study a low alloyed steel was selected and heat treatments including austenization, quenching and tempering were applied to it to obtain a hardened matrix. After heat treatments two steel plates ha-ving hardnesses of 315 and 320 HV were subjected to ballistic shots as target materials. The shots were carried out at 0° from a distance of 30 m to the target materials using API 55-7.62 mm armor piercing projectiles with a velocity of 835–840 m/s. Metallographical and fractographical examinations were carried out after the shots to investigate the behaviour of matrix under dynamic loading and to observe the formation as well as type of adiabatic shear bands and their effects on the nucleation and propagation of cracks within the matrix, in addition to the inclusions. In the etched samples a degenerated matrix compared to the original tempered martensitic-bainitic matrix was observed in the regions close to the penetration. On the other hand deformed and transformed types of adiabatic shear bands were observed as white bands. It is concluded that both types of adiabatic shear bands directly play an important role in the nucleation and propagation of cracks in addition to the inclusions within the matrix.