High-pressure torsion induced microstructural evolution in a hexagonal close-packed Zr alloy

Transmission electron microscopy was used to investigate the microstructural evolution of a hexagonal close-packed Zr alloy subjected to high-pressure torsion at 3.8 GPa. Results show that an inhomogeneous grain size distribution was obtained at the early stages of deformation, which is unique to hexagonal structures. {(1) over bar 011} deformation twins, which have never been reported in Zr alloys, were observed in coarse grains but not in refined grains. The grain refinement mechanism is discussed based on the experimental observation. (C) 2009 Acta Materialia Me. Published by Elsevier Ltd. All rights reserved.