Dynamic strain aging at the room temperature of near-α MgLi alloy: A study of dislocation substructures

As-casted Mg-5.5 Li-0.5 Y alloy was tension at different strain rates. A serrated flow with several remarkable drops was only observed when samples deformed at 10⁻⁴ s⁻¹. The sudden drop of flow stress mainly existed in the strain lower than 0.03, and the plastic instability disappeared at the larger strain. The strain rate jump test proved that the alloy exhibited a negative strain rate sensitivity at 10⁻⁴ s⁻¹, which is a sign of dynamic strain aging (DSA). The difference in flow behavior indicates the deformation behavior of MgLi alloys largely depends on strain rate. The dislocation configuration in the samples deformed at different strain rates is different. The dislocation density of the DSA sample is relatively low and most of the dislocations were basal <a > slip. DSA promoted jog climb of dislocation and the climb induced the dislocation transferred to another basal plane and further glide, which forms a series of dislocation bows and dipoles. Besides the job climb, the formation of stacking faults is another characteristic of the sample deformed at 10⁻⁴ s⁻¹. The solute atoms are segregated at the stacking faults, which shows a strong pinning effect on dislocation movability. Inhabitation of the glide induced a high strength and work hardening rate when the sample tension was at 10⁻⁴ s⁻¹.