  Microstructural analysis of a Mg-Zn alloy deformed at room temperature by
high-pressure torsion (HPT) indicates that fine-scale precipitation occurs even
without post-deformation heat treatment. Small-angle X-ray scattering detects
precipitates with radii between 2.5-20 nm after one rotation, with little
increase in particle size or volume fraction after 20 rotations. High
resolution electron micrographs identify grain boundary precipitates of
monoclinic Mg$_4$Zn$_7$ phase after three rotations and MgZn$_2$ after 20
rotations.
