Microstructure and mechanical properties of the AA6082 aluminium alloy with small additions of Sc and Zr

The effect of Sc and Zr addition on microstructure and hardness development in a commercial as-cast and solution-treated (530 degrees C/45 min) AA6082 alloy was studied. The electrical resistivity decrease and hardness increase in the temperature range 180-300 degrees C are caused by precipitation of beta '' and/or beta' needles of the Mg-Si system. Precipitation and morphology changes of Al-Mn-Fe system phases in AA6082 and AA6082-ScZr alloys influence the resistivity significantly, but have a negligible effect on hardness. The initial hardness of Sc and Zr containing AA6082 alloys is higher mainly due to the presence of Al(3)(SC, Zr) particles. This difference is less pronounced in the peak-hardening state. Natural ageing of solution-treated allos influences microstructure development in both alloys when annealed subsequently up to 240 degrees C.