Abstract
Unhomogenized commercial purity Al-1%Mn alloys containing Si about 0.4% or more have an exceedingly coarse recrystallization structure when rapidly heated for a short annealing time. Prolonged annealing or slow heating to the annealing temperature leads to a fine grained structure, because a number of nuclei generate in such a coarse recrystallized structure depending on the annealing time even in such Al-Mn alloys. Si0.2% or more in the homogenized Al-1%Mn alloy remarkably intensifies the effect of heating rate on the grain size of the alloy, but such an effect of Si is moderated with Si0.4% or more. These effects of Si on the grain size are prevented to an appreciable degree by coexistence of Fe or Mg and Si. The addition of Mg about 0.2% to Al-1%Mn alloy is effective to refine recrystallized grains.
