Behavior of Thermo-Mechanically Processed AA 6082 Aluminium Alloy Impacted by Conical Projectiles

AA 6082-T6 extruded flat bars were reduced to four different thicknesses, viz., 2 mm, 3 mm, 4 mm and 5 mm, using room temperature rolling and subsequently solution treated to obtain homogenized grain structure. These solution treated plates were subjected to cryogenic temperature rolling by immersing in liquid nitrogen before each pass to achieve thickness reductions of 50%, 66.66%, 75% and 80% to 1 mm final thickness. These samples with different cryogenic rolling strains and the same final thickness, clamped on the periphery, were subjected to normal high-speed impact by conical nosed cylindrical projectiles over a velocity range of 50–250 m/s and the projectile impact and residual velocities were recorded. These experimentally measured projectile impact and residual velocities were fitted into Lambert and Jonas model to characterize its parameters. Predicted Lambert and Jonas ballistic limit velocity wise, the samples with 75% reduction performed better when compared with other reductions. The maximum (i.e. 72.5 J) and the minimum (i.e. 15.28 J) energies were dissipated by the sample with 66.66% reduction shot at impact velocity of 216.99 m/s and the sample with 80% reduction impacted at velocity of 243.49 m/s, respectively. The samples with 66.66% reduction demonstrated outstanding energy dissipation, especially at higher impact velocities, in contrast to the samples with other reductions.