Non-basal slip in magnesium-lithium alloy single crystals

Abstract

Magnesium-lithium single crystals were stretched in the [112̄0] direction to investigate the deformation behavior by non-basal slip. {112̄2}〈1̄1̄23〉 second order pyramidal slip is activated in magnesium -3.5 at%, -7.5 at% and -10.6 at% lithium alloy single crystals, and its yield stress shows anomalous temperature dependence in the range from 77 K to 293 K. The yield stress due to the pyramidal slip decreases with addition of lithium. The deformation model due to the pyramidal slip is investigated by the observation of slip bands. Narrow slip bands are formed at lower temperature just after yielding. The width of slip bands at yielding increases continuously with increasing temperature and covers the whole specimen surface at 293 K. The results of the observation by TEM showed that double cross slip of (c+a) screw dislocations occur more frequently during deformation at 293 K than at 133 K. Many a and c edge dislocations are also observed in the crystals deformed at 293 K. The deformation mechanism of magnesium-lithium alloy is similar to that of cadmium.