Effect of precipitates on the dominant active slip systems in Mg-4.5Zn (wt.%) alloy

The dominant active slip systems during plastic deformation of an extruded Mg-4.5Zn (wt.%) alloy with and without β1′ precipitates were investigated by means of advanced electron back-scattered diffraction techniques and transmission electron microscopy. Planar slip traces were found in 92% of the grains with slip traces in the sample without precipitates and, among them, the primary active slip systems were basal slip and pyramidal II <c + a> slip. However, non-planar slip traces were observed in 76% of the grains with slip traces in the sample with precipitates, and among them, prismatic slip exhibited the highest activity, followed by pyramidal II <c + a> slip. The change in the dominant active slip systems with precipitation was attributed to the strong hardening induced by β1′ precipitates on basal slip. This favoured the cross-slip of basal slip dislocations to prismatic plane and plastic deformation progressed by the glide of prismatic slip dislocations parallel to the precipitates.