Effect of Mn Content on Tensile Properties of Rolled AZ31 Magnesium Alloy Sheet

Samples of Mg-3%Al-1%Zn(AZ31) alloy containing 0∼0.5 mass%Mn were prepared. They were then hot rolled and subsequently annealed. The effect of the amount of Mn content on their microstructures and deformation behavior during tensile tests was investigated. As Mn content increases, a large amount of Al-Mn compounds is crystallized in the alloys. The grain sizes of hot rolled specimens are significantly reduced but there is only a slight difference in the grain size of each alloy. After annealing for 1 h, significant grain growth occurs in 0%Mn alloy. On the other hand, the grain growth is sufficiently suppressed at 0.15%Mn content but it is hardly affected by further Mn addition. The tensile strength and 0.2% proof stress are improved by Mn addition of 0.05% or more, but those of the 0.1%∼0.5%Mn alloys are almost the same, because particles of Al-Mn compounds do not contribute to the strength of the alloys. In the annealed specimens, larger elongations are obtained in 0.15%Mn-containing alloy than in other alloys due to activation of non-basal slip and uniform elongation without deformation band.