Mechanical annealing of cryorolled Zr

Thermal annealing is usually employed to enhance the ductility of deformed materials, but always leads to a great loss in strength. In this study, we report an abnormal mechanical annealing behavior, i.e. a significant reduction of dislocation density with increasing compression strain, in the cryorolled Zr treated with high-pressure confinement deformation. A good combination of high strength and ductility has been achieved in the mechanically annealed sample. This unusual mechanical annealing behavior results from the motion of preexisting high-density dislocations in the cryorolled Zr under high stress. The high ductility of the mechanically annealed sample is attributed to the restoration of work hardening capability and grain boundary related deformations, while the high strength is due to the formation of nano-scale subgrains and grains in the sample. The observed mechanical annealing phenomenon can be employed to tailor microstructure and enhance the mechanical properties of deformed materials, and thus is of wide interest for the development of advanced structural materials with high strength and ductility.