Effect of oxygen content on impact toughness of a fine-grained magnesium alloy

Fine-grained Mg-3Al-Zn alloys with various oxygen contents were prepared by a powder metallurgy process, and the effect of oxygen content on the impact toughness of the fine-grained magnesium alloys was quantitatively investigated. It is found that the impact toughness of magnesium alloys with mean grain size smaller than 3 μm is extremely high when the oxygen content is less than 400 pp, but it becomes very low as the oxygen content is higher than 1000 ppm. Both magnesium oxides and hydroxides are detected in the magnesium alloys. The presence of excessive magnesium oxides and hydroxides deteriorates the dynamic plastic deformation ability of the fine-grained magnesium alloys.

► The effect of oxygen content on impact toughness of Mg alloy is quantitatively investigated.
► High toughness is achieved as mean grain size < 3 μm and oxygen content < 400 ppm.
► When the oxygen content is more than 1000 ppm, the toughness becomes very low.
► Magnesium oxides/hydroxides deteriorate plastic deformation ability of Mg alloys.