Fabrication and Ballistic Performance Evaluation of B₄C/AA7075 Functionally Graded Materials for Armor Applications

Functionally graded materials have shown a better ballistic performance against high-velocity ballistic impacts by increasing the ceramic reinforcement percentage in the metal matrix. In this study, B₄C/AA7075 FGM samples of 50 × 50 mm in size were prepared through the hot compaction powder metallurgy route. The three-layered FGMs were prepared based on the power law index (m = 1 and 2.5). The areal density of fabricated FGMs was less than 30 kg/m², and their ballistic performance was measured against a 7.62 × 39 mm HSC bullet. Relative density values of more than 98% were found in two types of samples. The maximum microhardness of the top hard layer of the type N2 (m = 2.5) FGM sample was found to be 13.35% higher compared to the type N1 (m = 1) FGM sample. The depth of penetration (DOP)-based ballistic performance results at 750 m/s have shown N2 FGM samples with 17.59% improved ballistic efficiency than the N1 FGM sample. After the bullet impact, the microstructure and morphology of the target surface were examined; this revealed the formation of micro-cracks, microvoids, and melted metal getting rapidly solidified. Furthermore, the abrasive and adhesive wear also contributed to reducing the projectile velocity.