Effect of Grain Size and Annealing Treatment on Steady State Creep of Copper

摘要

Randomly oriented polycrystalline copper of 99.995% purity was tested in tension at temperatures of 626, 496 and 406C. The grain size range investigated was from 0.03 mm to 0.7 mm. Grain sizes were produced by two techniques: (1) varying the amount of prior cold work and the annealing time at constant annealing temperature so as to obtain various recrystallized grain sizes with minimum grain growth and (2) holding the prior cold work constant while varying the annealing time or temperature so as to obtain varying grain sizes by grain growth. Polycrystalline samples (grain size of 0.03 mm) with a strong (001) (100) texture were also studied. The relationship between the steady state creep rate, and grain size was found to be the same independent of the technique used to prepare the various grain sizes. For specimens with grain diameters above 0.1 mm, the steady state creep rate appeared to be independent of grain size while for smaller grain diameters, the steady state creep rate increased slightly with decreasing grain size. Strongly textured polycrystalline copper, which contained low angle grain boundaries, exhibited steady state creep rates that were slightly lower than those observed in randomly oriented copper of the same grain size. The results are explained by considering the contribution of grain boundary shearing to the total strain and the effect of grain size on the resulting creep substructure. (Author)