Deformation mechanisms of β-Li in Mg-Li dual-phase alloy and effects of surface oxide layer

This study investigates the deformation mechanisms of beta-Li micropillar prepared from a Mg-7Li dual-phase alloy with or without surface oxide layer. The beta-Li micropillar with three cross-sectional sizes, 2.5 x 2.5 mu m2, 4.0 x 4.0 mu m2 and 5.5 x 5.5 mu m(2), are studied. The results show that the oxide layer improves the strength of micropillar due to the dislocation trapping effect. When increasing the micropillar size, the oxide layer having nanoporous structure becomes relatively thinner, and the strengthening effect resulting from the oxide layer decreases. Regardless of the existence of the surface oxide layer, all beta-Li micropillars show continuous deformation characteristics. This is ascribed to the interactions between pre-existing dislocations and non-planar dislocations activated during compression, which induces low-angle grain boundary and effectively traps the dislocations at the central area.