Deformation behavior of a dual-phase Mg-Li alloy at cryogenic temperatures investigated using in-situ neutron diffraction

Gong, W.; Gholizadeh, R.*; 川崎 卓郎; 相澤 一也; Harjo, S.

no journal, , 

The Mg-Li alloys consisting of hcp and bcc dual-phase microstructures exhibit superior ductility at room temperature, which has attracted significant attention in recent years. In contrast, these alloys consistently show poor work-hardening ability and resultant low strength at room temperature. The lack of work-hardening ability is likely due to the easy dislocation recovery in the bcc phase. It is well known that dislocation recovery can be suppressed by decreasing the deformation temperature. However, studies on the cryogenic deformation behavior of these dual-phase Mg-Li alloys are very limited. In-situ neutron diffraction, as a powerful microstructure probe, is reliable for tracking globally averaged crystallographic information associated with microstructure evolution and deformation behavior in structural materials at various environments. In the present study, we investigated the deformation behavior of a dual-phase Mg-Li alloy at cryogenic temperatures using in-situ neutron diffraction. The yield stress of the alloy increased consistently with decreasing deformation temperature. The work hardening was remarkably enhanced at 77 K and 20 K, leading to simultaneous improvements in ultimate stress and uniform elongation compared to 298 K. Dislocation multiplication was much faster at cryogenic temperatures, contributing to the improved work-hardening ability.