Microstructural changes in high interstitial stainless austenitic steels due to ballistic impact

Austenitic steels containing 18–19 mass% Cr and Mn each and about 1 mass% of C + N were impacted by 7.62 mm projectiles. In spite of their outstanding fracture energy in common tensile tests, discs of 5 and 10 mm thickness were perforated at a velocity of 830–840 m/s. A microscopic investigation revealed a net of adiabatic shear bands which localised the deformation and prevented the high absorption of energy encountered at slow speed. Cold work hardening by prestraining may improve the ballistic behaviour but would be difficult to apply to passenger car bodies.