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Experimental ballistic performance determination of friction stir welded magnesium (AZ31B) targets

Abstract Nowadays there is an increasing demand to develop light weight defense vehicles, fighter aircrafts and warships in order to enhance their mobility and fuel economy. It can be achieved by using the light weight structures made up of Aluminum and Magnesium plates which will reduce the weight, increase the payload carrying capacity and efficiency of the vehicles. In the present work, experimental ballistic performance of Magnesium (AZ31B) Base Metal (BM), friction-stir-welded (FSW) and post-weld-heat treated (PWHT) target plates have been determined by using the 7.62 mm Armor Piercing Projectiles (APP). Prior to ballistic testing, Magnesium joints were prepared by the FSW process for various tool rotational and welding speeds. Defect-free welds with better tensile and impact properties, were obtained with tool rotational speed of 1200 rpm and the welding speed of 50 mm/min. PWHT was carried out with the annealing temperature at 250 °C for about 1 hour. Microhardness and microstructure of the FSW and PWHT joints were investigated. Highest hardness (67 HV) was obtained for fine grain structure and precipitated particles were observed for PWHT targets. Depth of Penetration of PWHT target plates was approximately 17.55% and 16.31% lower than the BM and FSW target plates respectively. Scanning Electron Microscopic observation of projectile penetrated channel showed the formation of Adiabatic Shear Bands (ASBs). Due to a larger number of ASB lines, ballistic impacted FSW surface showed more number of macro cracks compared to PWHT surface. The PWHT joints showed the absence of fragmentation failure, lesser cracks and ASB lines which increased the ballistic performance.