Solute strengthening of prismatic slip, basal slip and {101?2} twinning in Mg and Mg-Zn binary alloys

摘要

Mg-Zn binary alloys with concentrations between 0 and 2.8 wt% Zn have been prepared and processed via hot rolling and annealing to produce specimens with a strong basal texture and a range of grain sizes. These have been deformed in three different strain paths: tension, compression and shear, in order to promote the dominance of prismatic slip, {101?2} twinning and basal slip, respectively. This experimental data has been used to create Hall-Petch plots for each deformation mode. It has been found that the prismatic slip system has a plateau in its Hall-Petch plot above grain sizes of ～30 μm, and solute softening of the prismatic system was found to be operative only at grain sizes above ～50 μm. In compression, the stress required to activate twinning was found to be insensitive to Zn concentration. It is proposed that solute softening and anomalous Hall-Petch behaviour of prismatic slip be understood in terms of the dominance of the cross-slip stress in coarse grained materials. The effect of grain size on the relative strength of basal slip, prismatic slip and {101?2} twinning is also discussed.