細粒多結晶亜鉛のぜい性―延性遷移圧力

Abstract

A pure zinc with mean grain diameters ranging from 15 to 19 μm was tested in tension and torsion under pressures at various strain rates to examine the difference between the brittle-to-ductile transition pressures found in both deformations, respectively. The results obtained here are summarized as follows:(1) The transition pressure of the fine grained zinc with a given grain size was always higher in tension than in torsion when deformed at a given strain rate as well as the transition pressure for the cast zinc.(2) The brittle-to-ductile transition for the specimen with a grain diameter smaller than 15.7 μm was caused when the hydrostatic stress component in the specimen reached a certain value irrespective of the deformation mode. Beyond 15.7 μm in grain size, however, the hydrostatic stress component at the transition pressure was algebraically smaller in the tensile specimen than in the torsion one.(3) In both tension and torsion, the transition pressure increased linearly with increasing logarithm of the strain rate encountered in the present experiment.