Thermal-activation parameters for asymmetric {211} slip in Li-Mg alloy crystals

Abstract

Differential deformation tests in compression have been made on Li-65% Mg alloy single crystals at temperatures between 4·2 and 293 K. Crystals covering a range of axial orientations were used and the strong temperature dependence of the flow stress was found to begin at ∼200 K. The results divide into two sets of data depending on the sense of shear on {211} slip planes. The activation volumes and enthalpies calculated from the data are not consistent with the classical asymmetric Peierls barrier model. It is suggested that the barrier energy is dependent on the sense of slip and that this is responsible for the stress asymmetry.