Effect of Zr addition on the microstructure evolution and mechanical properties of extruded Al-Cu-Li-Mn alloys

Abstract

The effects of Zr addition on microstructure evolution and mechanical properties of extruded Al-Cu-Li-Mn alloy were investigated during heat treatment processing. The recrystallization and grain growth were profoundly inhibited in solid solution-treated (SST) Al-Cu-Li-Mn-Zr alloy (Zr-containing), and massive substructures were retained, which were attributed to the higher Zener pinning pressure provided by Al3Zr dispersoids. But, complete recrystallization and considerable grain growth occurred in SST Al-Cu-Li-Mn alloy (Zr-free). Besides, the deformation textures containing Brass and S components were predominant in Zr-containing alloy, which contributed to a higher average Talyor factor (M) value. The higher strength behavior in SST Zr-containing alloy mainly originated from the extra Al3Zr dispersoids apart from the higher M value and dislocation density. The higher dislocation density and Al3Zr dispersoids in Zr-containing alloy promoted the precipitation of T1 phases and narrowed the width of precipitate-free zones (PFZs). Compared with Zr-free alloy, the enhanced combination of good strength and ductility shown in T6-aged Zr-containing alloy was mostly due to the higher T1 phase density and M value, higher dislocation density, and extra Al3Zr dispersoids.