Homogenization of a twin-roll cast thin Al-Mn strip

A sound homogenization practice was investigated for thin Al-Mn strips. The structure in the as-cast state reveals features typical of rapid solidification. The impact of subsequent hot rolling of the just solidified strip in the caster roll gap is also evident. A homogenization treatment makes a critical contribution by allowing the precipitation of excess Mn in solution. However, homogenized thin Al-Mn strips suffer coarse surface grains owing to the pinning of low and/or high angle grain boundaries by the fine dispersoids. However, homogenization improves the response to a subsequent annealing treatment in a profound way. The strip sample processed without a homogenization treatment softens very slowly, retaining high strength levels even after 3 h at 375 °C. In contrast, the homogenized strip samples soften fully when annealed at temperatures below 350 °C. Homogenization at the cast gauge is identified as the best practice, as prior cold rolling does not improve the grain structure or accelerate the softening behaviour of thin Al-Mn strip.