Rapid Grain Growth of Hot Extruded Al-Zn-Mg-Cu-(Sc) Alloy during Heat Treatment

Rapid grain growth and artificial aging characteristics during heat treatment is investigated for hot extruded Al-Zn-Mg-Cu-(Sc) alloys. Two Al-0.1wt%Sc alloys with different alloying element content are hot extruded to make T-shape bars at 380°C, and then the bars are solution treated for 2 hours at 480oC followed by artificial aging for 24 hours at 120°C. Microstructural evolution of the hot extruded bar is analyzed with optical microscope and electron back scattered diffraction (EBSD) mapping. Two kind of extruded bar shows different grain growth behavior at surface region and different artificial aging characteristics. The interaction between the precipitates and the grain growth during the heat treatment is thought to be responsible for the different grain growth behavior.