SOLID SOLUTION STRENGTHENING OF MAGNESIUM SINGLE CRYSTALS .2. EFFECT OF SOLUTE ON EASE OF PRISMATIC SLIP

Single crystals of Mg and a series of alloys containing Zn and Al solute have been deformed in tension over a range of temperatures in an orientation such as to induce first order {101̄0}〈112̄0〉 prismatic slip while suppressing both basal slip and {101̄2} twinning. At low temperatures the CRSS for prismatic slip decreases continuously with the addition of solute. At higher temperatures, however, the CRSS increases at low solute concentrations followed by a decrease at higher solute levels. The results can be best explained in terms of an increase in the athermal component and a decrease in the thermally activated component of the flow stress, with alloying. The observations also suggest that the decrease in the height of the Peierls' barrier, which is shown to be the rate controlling step in prismatic slip of Mg and its alloys, is not necessarily associated with a decrease in the axial ratio ( c a) nor with the monovalent nature of the solute. © 1969.