Evolution of microstructure and precipitates with cycle annealing temperature of an Al-6Mg-Mn-Sc-Zr alloy

The effect of cycle annealing temperature on the grain structure and precipitates of an Al-6Mg-Sc-Zr alloy was studied. It was found that the deformation grain structure was very stable between 200-500°C, and the alloy maintained a microhardness of about 110 HV/Mpa up to 450°C, indicating recrystallization of the cold rolling alloy was strongly inhibited in cycle annealing treatment. The evolution of the primary Al₃(Sc, Zr) and (Fe, Mn)Al₆ precipitates in alloy was inconspicuous. The size of β-phase precipitates changed from fine dots into large, and it is distributed homogenously as a fine dispersion at lower temperature, then evolves into discrete, discontinuous particles along boundaries at 500°C. It is believed that this evolution of grain structure and precipitates with cycle annealing temperature was mainly due to the existence of the secondary Al ₃ (Sc, Zr) precipitates.