The effect of erbium on the microstructure and mechanical properties of Al–Mg–Mn–Zr alloy

The influences of erbium (Er) on the microstructure and mechanical properties of Al–Mg–Mn–Zr alloys have been investigated. It has been found that about 0.2 wt.% Er can be dissolved in the matrix, excess Er atoms segregate at grain boundaries to form primary Al3Er. Addition of 0.4 wt.% Er refines the grain size of the as-cast alloy due to the formation of primary Al3Er. The solid solution decomposes to form a dispersion of secondary Al3Er, with facets parallel to {1 0 0} and {1 1 0} planes, during homogenization at 470 °C. The secondary Al3Er precipitates improve strength, especially the elevated temperature strength. The yield strength, at 150 °C, of the alloy with 0.2 wt.% Er is 50% higher than that of the Er-free alloy. The recrystallization temperature of the alloy with 0.4 wt.% Er is about 25 °C higher than that of the alloy without addition of Er.