Effect of deep cryogenic treatment on the microstructural, mechanical and ballistic properties of AA7075-T6 aluminum alloy

Abstract

The study focused on investigating the effect of Deep Cryogenic Treatment (DCT) on the mechanical and ballistic properties of AA7075-T6 aluminum alloy. The microstructure, microhardness, tensile strength, and impact strength of the Base Material (BM) and DCT-treated 7075 samples were analyzed through metallographic analysis and mechanical tests. The microstructure of the DCT-treated 7075 samples revealed fine grains and a distribution of secondary phase particles. The tensile strength, impact strength, and microhardness of DCT-treated samples increased by 7.41%, 4%, and 9.68%, respectively, compared to the BM samples. The fractography analysis of the tensile samples showed cleavage facets, microvoids, and dimples in both the samples. The ballistic behavior of the BM and DCT target plates were studied by impacting hard steel core projectiles at a velocity of 750 ± 10 m/s. The target plates failed due to petaling and ductile hole enlargement, and the depth of penetration (DOP) of the DCT target was less than that of the BM target, indicating a higher ballistic resistance. The post-ballistic microstructure examination of the target plates showed the formation of an Adiabatic Shear Band (ASB) without any cracks. It was concluded that the DCT treatment improved the mechanical and ballistic properties of the aluminum alloy due to grain refinement and high dislocation density.

Keywords

• Deep cryogenic treatment
• AA7075-T6
• Mechanical properties
• Ballistic
• Adiabatic shear band