Recrystallization in Al-Mg Alloys after Hot Compression

Because the 5000-series aluminum alloys are not heat treatable, controlling their microstructures during de-formation processing to achieve fine grain sizes is par-ticularly important. Recrystallization during or imme-diately following hot deformation provides an opportu-nity for controlling grain size prior to cold deformation. The present study investigates the effects of magnesium concentration, temperature, and deformation rate on re-crystallization during and immediately after hot upset-ting. Three aluminum alloys with magnesium concen-trations of 0.0, 0.5, and 4.5 wt.% were upset at 400 and 500°C at fixed strain rates of 0.1, 1.0, and 10.0 s^-1. The specimens were rapidly quenched after upsetting to pre-serve their microstructures. Portions of the specimens were then annealed for 10 min. to allow static recrystal-lization. Cross-polarized optical microscopy was used to examine the as quenched and annealed specimens. These results are interpreted to explain microstructural evolution during and after hot deformation.