Work Hardening of Magnesium Single Crystals Deformed to Stage~B at Room Temperature

Magnesium single crystals of purity (99.8 wt%) deformed to stage B on the work-hardening curve at the temperature of 293 K and at a strain rate of $10^{-3} s^{-1}$ were investigated. The modified Bridgman method was used to obtain the crystals of the preferred orientation of (0001)〈$11\overline{2}0$〉 as primary slip system. By using the method based on the experimental gradient matrix, the activity of slip systems was obtained in magnesium single crystals deformed to shear strain 1.2 γ, where well developed stage B of work hardening was observed. It was shown that primary (0001)〈$11\overline{2}0$〉 slip system was dominant in the whole investigated range of the examined deformation. The observation and analysis of etch pits on the {$\overline{1}2\overline{1}0$} plane showed the heterogeneous distribution of dislocations formed during deformation into walls of dislocations perpendicular to the (0001) slip plane. The suggested model of work hardening of magnesium single crystals, which is worth taking into consideration, shows the influence of the long-range stress field derivating from the groups of dislocations arranged in dislocation walls.