Abstract
High-temperature plastic deformation behavior and the resulting microstructures of magnesium (Mg)-based supersaturated solid-solution alloys containing zinc (Zn) and/or yttrium (Y) have been thoroughly examined in a comparative study by means of various electron microscopy combined with microanalytical techniques. According to the results of compression tests measured for the alloys at constant testing temperatures ranging from room temperature (RT) to 300°C, it is admittedly found in common to the respective alloys that twinning of {1012}-tensile type dominates the deformation at lower temperatures but this gives way to dislocation-slip with a rise in temperature. Above all, Mg–Y–Zn ternary solid-solution alloys yield remarkably higher levels of flow stresses capable of withstanding high temperatures than binary counterparts. The solid-solution alloy of Mg–0.6Y–0.3Zn (at%) subjected to compression at 300°C, in fact, has many deformation-induced stacking-faults on the (0001) basal planes significantly decorated by Y/Zn-solute segregation, providing the definite evidence that Suzuki effect actually contributes to a substantial enhancement of the flow stresses at elevated temperatures. This study demonstrates that the Suzuki effect is measurably activated in Mg-based solid-solution alloys, especially when those containing an adequate amount of combined solutes of Y and Zn, e.g. 0.6∼1 at%Y and 0.3∼0.5 at%Zn, are plastically-deformed at a temperature of 300°C and at a strain rate of 1.0 × 10−3 s−1.
Fig. 12 Atomic resolution HAADF-STEM images showing dislocation structure typically found in the 300°C-compressed alloy of Mg–0.6Y–0.3Zn, which were taken in the [2-1-10] incidence.
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