極低温でのオーステナイト鋼のセレーション変形におよぼす試験条件の影響

抄録

Tensile deformation behavior of metals at very low temperatures has been investigated using mainly Fe-42%Ni alloy in order to make sure the applicability of the computer simulation method presented by the authors and to clarify effects of testing conditions on serration. The amount of elongation accompanied with each load drop in serration increased with the increase in deformation rate and with the decrease in gauge length. Hourglass type specimen showed serration similar to that observed in specimens with smoothly reduced section. Serration was smaller in liquid He(II) than in liquid He(I). All these characteristics of serration observed experimentally were produced by computer calculation. Using computer simulation, it was clarified that the increase in thermal conductivity and diffusivity decreased the amount of elongation accompanied with load drops in serration. Simulation also showed that work hardening played an important role in determining serrated deformation behavior at very low temperatures. However serration was observed even when work hardening was not considered in calculation and specimen was deformed only at the central region of the specimen. Deformation behavior observed experimentally was discussed using such results obtained by simulation.