Contributions of multimodal microstructure in the deformation behavior of extruded Mg alloys containing LPSO phase

The control mechanisms of the plastic deformation of two-phase extruded alloy composed of Mg and long-period stacking ordered (LPSO) phase were clarified by comparison with those of other Mg solid-solution alloys. The stress-strain curves for each grain in the alloys could be imaginary estimated using neutron diffraction analysis during the tensile test. The deformation behaviors of the worked and recrystallized grains are significantly different in all the Mg-extruded alloys owing to the strong plastic anisotropy in Mg with hexagonal close-packed (hcp) structure. Therefore, the deformation behavior is controlled by a composite-like deformation mechanism. In Mg-Y-Zn ternary alloys, the recrystallized Mg grains exhibited significant lattice softening at the initial stage of yielding. However, the worked grains acted as strengthening components. In the Mg/LPSO two-phase alloy, the composite-like deformation behavior was enhanced, and the LPSO phase significantly contributed to the strengthening of the alloy. Moreover, it was hypothesized that the LPSO phase contributes not only to the alloy’s strength but also to its elongation by increasing the work-hardening rate. Kink-band strengthening in the LPSO phase is believed to be one of the reasons for the increase in the work-hardening rate of the extruded LPSO-phase grains in the Mg/LPSO two-phase alloy.