Microstructure and mechanical properties of AZ31 magnesium alloy sheet by hot rolling

AZ31 magnesium alloy sheets with a thickness of about 2mm were prepared by using a unique hot rolling process which was featured by heating the rolls during rolling. Two different rolling routes were used to achieve the final thickness through 6 passes of rolling. The major rolling parameters were chosen as the same for both rolling routes except that the roll temperature was set to be 400°C for route A and the 1^st to 4^th passes of route B, but lowered to 350°C for the 5^th and 6^th passes of route B. The microstructure and mechanical properties of the alloy sheets were comparatively investigated. The results showed that dynamic recrystallization occurred during hot rolling, and by choosing the processing parameters appropriately the grain size could be refined steadily with increasing rolling passes. The final alloy sheet prepared by 6 passes of rolling via the rolling route B was featured by a very fine microstructure, with the grain size being 5μm in average. Correspondingly, it presented very high strength and tensile elongation, with its yield strength and tensile elongation achieving 206MPa and 26.4% in the transverse, and 196MPa and 27.6% in the rolling direction, respectively.