Effects of Magnesium Content on Ballistic Performance of Al-8Zn-SiC Composite after Heat Treatment Process

Abstract

SiC – reinforced aluminium composite - has been developed to improve the ballistic performance and mobility of the armour material. Critical to obtaining ballistic resistance is that the materials must be sufficiently hard and strong, especially at the surface where a projectile will first make impact. To achieve this resistance, aluminium alloys can be strengthened by adding Zn and Mg, and reinforced with silicon carbide. This research studied the ballistic properties of aluminium composites with varied Mg. The matrix used in this study was an Al-8Zn alloy with 3-5 wt. % Mg. Silicon carbide particulate of 15 % volume fraction was used as strengthening material, which was added to the liquid matrix by stirring at 5000 rpm. The liquid composite was then squeeze cast at a pressure of 72 MPa. Then the composites were heat-treated and coated to improve the ballistic performance. Ballistic testing was performed in accordance with ASTM F1233 by using 7.62 calibre projectiles. Microstructural observation was conducted in samples, performed with optical microscope. The results showed that the as-cast hardness of the composite increased with addition of Mg content of 3, 4 and 5 wt. %. The peak hardness after ageing at 200 °C also increased with Mg addition. However, the composites were not able to withstand the 7.62 mm calibre projectile.