Microhardness characterisation in developing high strength, high toughness and superior ballistic resistance low carbon Ni steel

To develop new steels that exceed the ballistic resistance, strength and toughness of current naval ship steel plates, we designed optimally quenching-lamellarising-tempering treated low carbon 10%Ni steel plates. These plates displayed exceptional properties in all aspects; when compared to the widely used HSLA-100 steel plates, they showed superior toughness and an improvement of over 15% in strength and 20 mm fragment simulation projectile ballistic limit V-50. A preliminary vibrating sample magnetometer study on the effect of quenching-lamellarising-tempering process and dynamic deformation on the microstructure evolution of the 10%Ni steel during ballistic impact was valuable to our understanding of the steel. The data led us to conclude that dynamic deformation during ballistic perforation induced an austenite to martensite phase transformation, which improves the global dynamic plasticity and ballistic resistance of the steel target. This mechanism, similar to the transformation induced plasticity effect, can be appropriately named ballistic induced plasticity. Characteristics of the microhardness maps of the sectioned craters created by ballistics are consistent with ballistic induced plasticity.