In-situ neutron diffraction study of cryogenic deformation behavior in AZ31 magnesium alloy

Gong, W.   ; Harjo, S.   ; Kawasaki, Takuro   ; Aizawa, Kazuya  ; Tsuji, Nobuhiro*

Magnesium (Mg) and its alloys, as the lightest structural metallic materials, have potential for application under various environments. Here, in-situ neutron diffraction experiments were conducted for investigating the deformation mechanisms at cryogenic temperature in an AZ31 Mg alloy. A commercial extruded AZ31 alloy was used, while the loading direction was parallel to the extrusion direction. In-situ neutron diffraction experiments during tensile and compressive deformation at 21K and 298K tests were performed using a time-of-flight engineering diffractometer -TAKUMI at Japan Proton Accelerator Research Complex (J-PARC). The yield stress increased significantly with decreasing deformation temperature in tensile deformation, but increased slight in compressive deformation. Interestingly, the fracture strain and stress at 21 K increased simultaneously compared to that at 298 K in compressive deformation. The lattice strain and the volume fraction of extension twins were calculated by the variation of diffraction profile. The deformation mechanisms including basal slip, extension twinning, and contraction twinning were quantitatively evaluated by lattice strain and texture results. The different sensitivities of various deformation modes to temperature are responsible for the variation of macroscopic deformation behavior with temperature in AZ31 alloy.