Twinning related plastic mechanism of a magnesium alloy at a high strain stage of ambient sheath extrusion

Ambient sheath extrusion was conducted on a magnesium alloy, in which a true strain as high as 68% was attained. Twinning was found prevalent during extrusion, thus transmission electron microscopy (TEM) was employed to investigate the plastic mechanism for both twinned and matrix regions. Although twinning created much softer orientation inside hard matrix, which facilitated basal slip, a⇀+c⇀ slip was frequently observed inside twin lamellas without evident influence from the local crystal orientation. In matrix, on the other hand, a⇀+c⇀ slip also participated as an important plastic mechanism and band structures were formed preferentially on the {101¯0} plane, which led to continuous orientation gradient.