Non-basal slips in magnesium and magnesium-lithium alloy single crystals

Magnesium and magnesium - lithium single crystals were stretched in [1120] direction to investigate the deformation behavior by:non-basal slips. In the case of magnesium, {1122}< 1123 > second order pyramidal slip is active in a range from 77K to 293K and the yield stress decreases with increasing temperature in a range from 77K to 133K, while the stress increases with increasing temperature above 133K. Second order pyramidal slip is also 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 similar to the case of pure magnesium. The deformation mode due to the pyramidal slip is investigated by observation of slip band. 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 293K. The results of the observation by TEM showed that double cross slip of (c+a) screw dislocations occur more frequently during deformation at 293K than at 77K. At 293K, there are few (c+a) edge dislocations, while many a and c edge dislocations are observed in the crystals. The yield stress due to the pyramidal slip decreases with addition of lithium.