Characterization of deformation behaviour and fracture mode of recycled aluminium alloys (AA6061) subjected to high-velocity impact

Abstract

Recycling aluminium alloys have been shown to provide great environmental and economic benefits. The global demands placed upon recycled aluminium and its product has further increased the need for better understanding and prediction of the deformation behaviour of such materials subjected to various dynamic loading conditions. It is also a topic of high interest for both the designer and the user of metal structures, specifically in the automotive industry. Even though numerous efforts have been made to improve recycling processes of aluminium alloys, very little attention is given on the fracture behaviour related damage and anisotropy during impact. In this study, therefore, the anisotropic-damage behaviour of the recycled aluminium alloys (AA6061) is examined via Taylor Cylinder Impact test. A gas gun was used to fire the projectiles towards a target at impact velocity ranging from 170m/s to 370 m/s. The deformation behaviour, including the fracture modes, digitized footprint and side profile of the deformed specimens, are observed and analysed. Scanning Electron Microscope (SEM) is further used to observe the damage behaviour, including microstructural changes of the impact surface. The damage progression is also analysed by observing the microstructural behaviour of location 0.5 cm from the impact area. General speaking, there are three different types of ductile fracture modes (mushrooming, tensile splitting and petalling) can be observed in this study within the impact velocity range of 170m/s to 370m/s. The critical impact velocity is defined at 212 m/s. The digitized footprint analysis exhibited a non-symmetrical (ellipse-shaped) footprint where the footprints showed plastic anisotropic behaviour and localized plastic strain in such recycled material. The damage evolution of the material is increasing with the increase in impact velocity.