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 {100} and {110} planes, during homogenization at 470 degrees C. The secondary Al3Er precipitates improve strength, especially the elevated temperature strength. The yield strength, at 150 degrees 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 degrees C higher than that of the alloy without addition of Er. (C) 2009 Elsevier B.V. All rights reserved.