Enhanced superplasticity and diffusional creep in ultrafine-grained Mg–6Al–1Zn alloy with high thermal stability

Ultrafine-grained Mg–6Al–1Zn alloys, which have β-Mg17Al12 70–140 nm particles preferentially located at the grain boundaries, exhibited excellent thermal stability and superplasticity at high temperatures. Diffusional creep (Coble creep), which has rarely been reported in other ultrafine-grained Mg alloys and composites, becomes dominant over the grain boundary sliding mechanism at strain rates near 10−4 s−1 at 523–573 K.