Investigation on a ferrite-based low-density steel composite plate with crossed-laminated structure and its ballistic penetration characteristics

In this study, from the viewpoint of reducing the weight of a steel/steel composite plate, a ferrite-based low-density steel composite plate composed of A-side with density of about 7.15 g·cm−3 and B-side with density of about 7.10 g·cm−3 was fabricated using electroslag remelting followed by hot forging. The microstructure and properties of the composite plate and its ballistic penetration characteristics were investigated. The microstructures of the A-side and B-side were characterized by crossed-laminated microstructure composed mainly of banded δ-ferrite and α-ferrite distributed between the bands. The content, length, and width of the banded δ-ferrite on the A-side were respectively lower or smaller than those on the B-side. The hardness and compressive strength of the A-side respectively being about 420 ± 6 HV0.5 and 2250 MPa were higher than those of the B-side respectively being about 326 ± 12 HV0.5 and 1808 MPa. The microstructure and composition of the miscibility zone with a thickness of about 45 µm between the A-side and B-sid had no obvious difference with its adjacent side. No intermetallic compounds could be identified in the miscibility zone. The composite plate could resist the vertical ballistic penetration of 7.62 mm-caliber armor piercing incendiary projectile with an initial velocity of about 800 m/s at 50 m from the plate. When ballistic penetration was conducted from the A-side, the projectile could not reach the miscibility zone and the microstructure and fracture characteristics of the projectile hole was dominated by shear bands (SBs) and dimples. When ballistic penetration was conducted from the B-side, the projectile could pass through the miscibility zone and reach A-side but could not penetrate the A-side; and the microstructure and fracture characteristics of the projectile hole was dominated by cracks and local rheological. The main reasons for the different ballistic penetration characteristics near the projectile hole formed by ballistic penetration from A-side and B-side were attributed to the different microstructure and properties between both sides. The crossed-laminated structure in A-side has a positive effect on the anti-penetration properties of the composite plate.