STRUCTURE AND STRENGTH OF SUBMICROMETER-GRAINED COPPER

Samples of pure copper with submicrometer-grained microstructures have been produced by severe plastic deformation and annealed at temperatures from 373 to 493 K. Annealing up to 423 K does not result in grain growth and the general appearance of the structure of the annealed specimens as seen by TEM does not deviate from the as-deformed state. Grain growth starts above 423 K. The internal stresses measured through the X-ray diffraction peak widths gradually decrease at low annealing temperatures and practically vanish at temperatures higher than 423 K. The annealing temperature dependence of macroscopic strength of the samples correlates with the variation of the internal stresses. Possible micromechanisms of the observed recovery of material properties are discussed.