Effects of yttrium on creep behavior and deformation substructures of magnesium

Compressive creep behavior and deformation substructures of binary Mg-Y(-Zn) alloys were investigated at 550K similar to 650K under 4 similar to 200MPa. Creep strength of magnesium is significantly improved by addition of yttrium as compared with Mg-3mol%Al solution hardening: alloy. The small addition of zinc (less than 0.1mass%) to Mg-Y binary alloys is effective to decrease creep rate by more than one order of magnitude. This effect is remarkable in solid-solution state and diminishes in precipitation-hardening alloys. TEM observations reveal that many 'planer defects' with a+c-component are introduced on the basal planes in Mg-Y-Zn alloys. These defects can act as the obstacles for dislocation motion and high strain-hardening increases creep resistance of Mg-Y-Zn alloys.