Influence of Cold Rolling and Annealing on the Mechanical and Corrosion Properties of an AA5182 Al-Mg Alloy

Abstract

Wrought Al-Mg alloys are important and promising material for application in transportation industry primarily due to favorable strength to weight ratio. As a result of their usage in the field of transportation, the weight of vehicle constructions become reduced, resulting in a decrease of fuel consumption and carbon dioxide emissions. In addition to these advantages, one of the important demands on the application of Al-Mg alloys as a light weight structural material, is providing a high strength, corrosion resistance and good surface quality without relief caused by yield point phenomena and serrated flow. Such a good combination of properties can be achieved by a variation and optimization of thermomechanical processing parameters including a degree of deformation and annealing conditions. In this study we investigated the effect of cold rolling reductions and different annealing conditions, on the corrosion resistance and mechanical properties of an AA5182 type Al-Mg alloy. Material was industrially produced and supplied by Impol-Seval Aluminium Rolling Mill, Sevojno, Serbia, as hot rolled 12 mm thick plates. Further lab-processing of hot rolled plates included cold rolling with 40-85% reduction in thickness, and annealing in the range of temperatures 280-350°C, in a different period of time. Annealed specimens were used for room temperature tensile testing while corrosion testing was performed on the annealed and sensitized specimens. Intergranular corrosion (IGC) susceptibility was determined by nitric acid mass loss test (NAMLT) for the selected states. The results showed that corrosion resistance, tensile strength and yield point elongation were mostly affected by a degree of cold deformation. It was found that increasing in cold rolling reduction from 40-85% before annealing causes an improved strength level due to grain size refinement. However, yield point elongation became more pronounced and a tendency towards Lüdering as undesirable surface appearance was increased. NAMLT testing showed that the material was corrosion resistant in as-annealed condition while it became susceptible to intergranular corrosion after sensitization treatment. IGC susceptibility of sensitized specimens increases with cold rolling reduction and a raise of annealing temperature.