Sc Microalloying Improved Heat and Corrosion Resistance of an Al-Cu-Mg Alloy Under Varied Heat Treatment Processes

Abstract

2××× series Al-Cu-Mg alloys with high specific strength (strength/weight ratio), good formability, corrosion and heat resistance are widely used in the aerospace industry (e.g. fuselage structures). This paper reveals the effect of 0.2 wt% Sc microalloying on the hardness, heat and corrosion resistance as well as microstructure of an Al-4.3Cu-1.6Mg (wt.%) alloy under varied heat treatment processes using high-angle annular dark-field in scanning transmission electron microscopy and differential scanning calorimetry etc. The results show that Sc minor addition contributes to the improved heat and corrosion resistance of the peak-aged Al-Cu-Mg-Sc alloy under different solution and aging treatment parameters, despite of a slight decrease in peak hardness. The improved corrosion resistance of the peak-aged Al-Cu-Mg-Sc alloy is related to the formation of discontinuous grain boundary precipitates and narrower precipitation free zones. The increased heat resistance and slightly reduced peak hardness of the Al-Cu-Mg-Sc alloy compared to Al-Cu-Mg alloy are mainly due to the increased formation temperature and decreased number density of the main strengthening S precipitates by Sc.

Keywords: Al-Cu-Mg alloys, Sc microalloying, heat treatment process, Property, microstructure