Comparing the Influence of Mn and Fe Content on the Fracture of a AA6XXX Series Alloy in Different Aged States

Abstract

The objective of this study was to investigate and compare the influence of Mn and Fe additions on the fracture behaviour of AA6000 series alloys in under, peak and overaged conditions. Testing was completed under uniaxial tension and the microstructures of the alloys were observed using optical and Transmission Electron Microscopy. Alloys with very low levels of both Mn and Fe underwent a transition from transgranular to intergranular fracture and a reduction in strain-tofracture when heat treated from the under aged (UA) to peak aged (PA) condition. Increasing Mn and Fe content prevents this transition in fracture mode such that the stain-to-fracture is similar in the UA and PA states. Despite the change in fracture mode, when comparing the strain-to-fracture for a given ageing condition, increasing Fe systematically reduces the strain-to-fracture. Conversely, increases in Mn systematically increase the strain-to-fracture for a given ageing condition.