Effect of twinning on the mechanical behavior in Mg-Zn-Y alloys

In the present work, the effect of twinning on the mechanical behavior of Mg-Zn-Y alloys has been investigated by controlling the process condition and modifying the matrix. In order to study the effect of the deformation speed, we examined as-rolled Mg-6Zn-1.2Y by changing rolling speeds (32-64 mm/s). Dynamically recrystallized grain structure was developed under a lower rolling speed of 32 mm/s, while significantly twinned grain structure was obtained under a higher rolling speed of 64 mm/s. From the results of tensile test, uniform elongation increases from 5.3% to 7.3% with increasing rolling speeds. In order to study the effect of mechanical twinning on the mechanical behavior, we examined Mg-xZn-0.6Y alloys (x = 3-7). Mg-xZn-0.6Y alloys are consisted of α-Mg and icosahedral phase (I-phase) particles up to 7 wt% Zn. From the result of tensile test, the strength and elongation increase simultaneously with increasing zinc content in spit of similar grain size and similar volume fraction of I-phase particles. Detailed study by an interrupted tensile test shows that the volume fraction of twins in interrupted Mg-7Zn-0.6Y is higher than that in Mg-3Zn-0.6Y. Texture analysis shows that the type of twinning is (10-12) extension type twin. Therefore, it can be suggested that twinning leads to enhance strain hardening and reorient basal slip to more favorable orientations, improving the elongation in wrought Mg-Zn-Y alloys.