In Situ Annealing of Severe Plastic Deformed OFHC Copper
A pure OFHC copper is subjected to severe plastic deformation (SPD) by a well defined high pressure torsion process at ambient temperature. The change in microstructure of samples deformed to different strains, up to ε=64, is investigated in-situ, during annealing at 170°C, within a scanning electron microscope. The spatial distribution of nucleation sites changes significantly with increasing strain from nucleation at triple junctions and grain boundaries to a random distribution of sites for von Mises equivalent strains beyond ε=4. The resulting mean size of recrystallized grains is about 6.75 times larger than the mean microstructural size of the corresponding as-deformed state. For strains larger than ε=16 the recrystallized microstructure appears to be independent of preceding strain. A detailed investigation of the nucleation of recrystallized grains following very large strains shows that certain microstructural elements are favoured as nuclei and were particularly taken into account.
S.-J.L. Kang, M.Y. Huh, N.M. Hwang, H. Homma, K. Ushioda and Y. Ikuhara
S. Scheriau et al., "In Situ Annealing of Severe Plastic Deformed OFHC Copper", Materials Science Forum, Vols. 558-559, pp. 1345-1351, 2007