Investigation on ballistic behaviour of friction stir welded rolled AZ31B magnesium alloy

Abstract

In this paper, an attempt was made to study the ballistic resistance of Friction Stir Welded (FSW) AZ31B magnesium alloy. The base metal AZ31B plates were sliced to required size and FSW was carried out using a non-consumable taper pin tool made up of HCHCr steel. Samples were taken out from the FSW plates to study the microstructure and microhardness. The FSW AZ31B contain refined grains and tiny Mg₁₇Al₁₂ precipitates which were formed because of severe plastic deformation during FSW. The FSW AZ31B targets also showed ∼7.47% increase in microhardness compared to BM target. Further, ballistic test was conducted by impacting Ø7.62 × 39 mm hard steel core projectiles at an initial velocity of 420 m/s. AA6062 material of 25 mm was used as backing plate to measure the Depth of Penetration (DOP) of the projectile. The failure mechanism and the ballistic resistance of BM and FSW AZ31B samples were studied and compared. Finally, post ballistic analysis was made to study the failure modes of the target at microscopic level. Through various experimental results, it was identified that the increase in ballistic resistance of FSW AZ31B target was mainly due to two reasons; the refinement of grain size and small strengthening precipitates.