Negative Strain-Rate Sensitivity of Mg Alloys Containing 18R and 14H Long-Period Stacking-Ordered Phases at Intermediate Temperatures

The strain-rate sensitivity of a Mg-10Dy-1Zn (wt pct) alloy containing different long-period stacking-ordered (LPSO) phases has been investigated in the strain rate range of 10−3 to 1 s−1 from room temperature to 673 K (400 °C). Both alloys containing 18R-LPSO and 14H-LPSO phases show negative strain-rate sensitivity (–0.02 to –0.01) at intermediate temperatures [423 K to 523 K (150 °C to 250 °C)]. The serration behavior of the Mg-10Dy-1Zn alloy containing 18R-LPSO phase is related to dynamic strain aging. However, the appearance of serrated flow in the Mg-10Dy-1Zn alloy containing 14H-LPSO phase is mostly rooted in the formation of microcracks in \( \left\{ {10\overline{1} 2} \right\} \) planes.