超微細フェライトーセメンタイト鋼の静的引張特性に及ぼすセメンタイト体積率の影響

摘要

Effect of cementite volume fraction on stress-strain relations in ultrafine-grained ferrite-cementite (FC) steels was studied. The ultrafine-grained FC steels with various cementite volume fractions between 0.3 and 13.7% and average ferrite grain size of about 0.25 μm were prepared by carbon steels. Lower yield stress, tensile strength and flow stress increased with increasing of the volume fraction of cementite. Effect of dispersed cementite on the work-hardening rate in the present ultrafine-grained FC steels was discussed by using Ashby's theory. It is very important for the work-hardening rate of the ultrafine-grained FC steels to control or maintain the size of finely dispersed cementite. By using the experimental results, true stress (σ_(pdl)) and true strain (ε_(pdl)) at plastic deformation limit were calculated. Effects of the volume fraction of cementite and the grain size on the σ_(pdl)-ε_(pdl) balance were summarized from the viewpoints of yield strength and the work-hardening rate at σ_(pdl).%鉄鋼材料の高強度化の手段の一つとして，結晶粒微細化rn強化は大変有効であり，さまざまな手法による結晶粒微細rn化と作製された微細粒鋼の機械的特性に関する研究が進めrnられている。