Effect of Mg addition on the τ phase distribution of an AlMn alloys modified with zinc

The effect of Mg addition on the τ phase formation of an AlMn alloys modified with Zn, has been investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy, complemented by micro vickers hardness and galvanic efficiency. The results show the τ precipitates are formed when aged at 450 °C for 5 h in AlMnZn-(Mg) alloy with upper to 5.49% Mg addition. The hardness and galvanic efficiency value of the aged alloy with 5.49% Mg is always distinctly higher than that of the alloy in as-cast condition with the same composition. Based on microstructural and galvanic efficiency results the quantity of τ phase with Mg addition is discussed, in order to relate the τ distribution with the galvanic efficiency.