Effects of twin-boundary precipitates on twin stability and yield strength of a Mg-Nd-Ag-Zr alloy

Abstract

The effects of precipitates at {10 1‾ 2} twin boundaries on twin stability and yield strength of a Mg-Nd-Ag-Zr alloy are investigated by transmission electron microscopy and electron back-scattered diffraction. Twin-boundary precipitates are observed in the pre-deformed alloys after subsequent ageing treatments over a temperature range of 200–450 °C. Such twin-boundary precipitates significantly enhance the thermal stability of {10 1‾ 2} twins, which remain relatively stable even at 480 °C. The stress stability of {10 1‾ 2} twins is also improved due to the pinning effect of the twin-boundary precipitates, leading to a strengthening effect on the alloy. More twin boundaries can be introduced via pre-deformation at a much higher strain rate of 1000 s−1, and such dynamic pre-compression with subsequent ageing treatments is more effective in improving the yield strength due to the formation of more stable {10 1‾ 2} twin boundaries.