Achieving superior high-temperature strength in nanostructured Al-Cu-Mn alloy with Sc addition

The microstructure evolution and mechanical behavior at elevated temperatures have been studied in 90% cold-rolled Al-4Cu-0.8Mn and Al-4Cu-0.8Mn-0.2Sc alloys. The strength of the two alloys is similar at room temperature, while at 250°C and 300°C the strength of the Sc-containing alloy is almost twice that of the Sc-free alloy. It is demonstrated that the addition of Sc promotes θ′ precipitates, which stabilize the nanoscale microstructure induced during heavy rolling. The stabilized microstructure enables substantial boundary strengthening at elevated temperatures, contrary to the common assumption that this type of strengthening is not effective for improving high-temperature strength of aluminum alloys.