銅の引張変形中の動的再結晶

抄録

Dynamic recrystallization phenomenon in the tensile deformation of copper was investigated in order to clarify the deformation and the metallographic conditions under which the dynamic recrystallization appears. Cold-rolled specimens were tensiled preliminarily at various temperatures and a strain rate of 4.2×10^-4sec^-1. The stress-strain curves obtained showed plural maxima of the stress at temperatures above 250°C at which the specimens had already recrystallized statically before the loading. Optical and electron microscopic observations, a hardness measurement, and an X-ray diffraction experiment were carried out for water-quenched specimens after an interruption of the tensile deformation. These results showed that the plural maxima were attributable to strain hardening and dynamic recrystallization which became predominant one after another. A series of experiments on the effect of deformation temperature, strain rate and initial grain size on dynamic recrystallization were carried out for fully annealed specimens, as a function of the strain at the first maximum of the stress, ε_m, in the stress-strain curves. In the present investigation, ε_m decreased with increasing temperature and decreasing initial grain size, while ε_m had a minimum at the strain rate of 4.2×10^-5sec^-1. Finally, Cu-0.064, 0.12 and 0.26wt.% Sn alloys were prepared, from a consideration that Sn atoms suppress the static recrystallization of Cu-rich solid solution. The dynamic recrystallization of Cu-Sn alloys was also suppressed much in comparison with pure copper. This tendency became prominent with an increase in the amount of Sn.
The results obtained in the present study were discussed in reference to the dependence of deformation and metallographic conditions on the static recrystallization during the isothermal annealing.