Evolution of Microstructure and Precipitates with Cycle Annealing Temperature of an Al–6Mg–Mn–Sc–Zr Alloy

Abstract

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 Al3 (Sc, Zr) precipitates.