Numerical and experimental ballistic performance of welded magnesium (AZ31B) plates

In this work, the mechanical properties and ballistic performance of a friction-stir-welded magnesium (Mg) alloy (AZ31B) were studied using numerical and experimental techniques. The tensile properties and microhardness of the weldment were determined as per the ASTM E 08 and E 384-05 standards. The values of tensile properties and microhardness of the weldments were observed to be lower than those of the base metal (BM). Microstructural analysis of the nugget zone showed a discontinuous dendritic structure and less β-Mg₁₇Al₁₂ phase. The ballistic impact performance of the magnesium weldment and BM was analysed using a numerical code and validated by ballistic experiments. An armour-piercing projectile of 7.62 mm with an initial projectile velocity of 456 ± 10 m/s was considered for both studies. Primarily, numerical analysis was performed using the Abaqus 6.14 finite-element software with the Johnson–Cook failure criterion. For each ballistic impact test, the residual velocity of the projectile was measured. To validate the numerical observations, an experimental ballistic test was conducted as per the National Institute of Justice standard. The experimental residual velocity of each target was estimated using the Recht–Ipson analytical model. It was found that the ballistic performance of weldments was inferior (26%) compared with that of the BM target. A good correlation of residual velocity was noted for the numerical and experimental methods. Scanning electron microscopy analysis of the friction-stir-welding fracture surface showed adiabatic shear bands.