Twinning during Dynamic Strain Aging in binary Mg-3%Y alloy.

The extruded Mg–3 wt.% Y alloy exhibits serrated flow during compression tests along the extrusion direction at intermediate temperatures (150-250 ºC) and a wide range of strain rate (10 -2 to 3×10 -5 s -1 ) due to dynamic strain aging (DSA). The values of the m + β constant and the activation energy were 2 and 100 kJmol -1 , respectively. To elucidate the underlying deformation mechanisms, in-situ synchrotron radiation diffraction and acoustic emission (AE) experiments were conducted at 200 °C. The deformation process involves the activation of -dislocation slip on both basal and non-basal planes, as well as extension twinning, all occurring concurrently with DSA. The characteristic serrations arise from the dynamic interaction between diffusing yttrium atoms and mobile dislocations and twin boundaries. Yttrium atoms are shown to effectively pin -dislocations and inhibit twin boundary propagation, thereby influencing the overall mechanical response during deformation. The unpinning of twin boundaries from yttrium atoms induces a new additional cluster in the acoustic emission signal.