Microstructural evolution upon heat treatments and its effect on corrosion in Al-Zn-Mg alloys containing Sc and Zr

Abstract Different contents of Sc and Zr were alloyed into Al-Zn-Mg alloys: Alloy A (0 pct Sc + 0 pct Zr), Alloy B (0.19 pct Sc + 0.09 pct Zr), and Alloy C (0.19 pct Sc + 0.18 pct Zr). The combined alloying of Sc and Zr promoted the primary phase of Al-Zn-Mg alloys to dissolve into the matrix during cold rolling, and produced Al3(Sc,Zr) precipitates by subsequent aging. The combined alloying of Sc and Zr restrained the recrystallization of Al-Zn-Mg alloys, and caused finer and more uniform grains by the two-stage solution. The distribution of texture was important to understand the microstructural evolution of alloys. The combined alloying of Sc and Zr with the two-stage solution promoted the increase of the cubic texture {001} . The microstructural evolutions including the Al3(Sc,Zr) precipitates, the precipitation free zone (PFZ) width, the textures and the recrystallizations were the main factors affecting the corrosion resistance of the Al-Zn-Mg alloys containing Sc and Zr. Alloy C after the two-stage solution treatment followed by the two-stage aging had the best stress corrosion cracking (SCC) resistance and the highest electrochemical corrosion resistant properties.