低炭素鋼の高Z因子大歪加工における超微細粒組織の形成

概要

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Ultrafine-grained structure formed dynamically through severe plastic deformation at elevated temperatures has been investigated in a 0.1%C-0.4%Si-1.5%Mn steel. The effects of the strain, the strain rate and the deformation temperature on the micorstructural evolution were examined using a compression technique with a pair of anvils. The maximum strain was 4, the deformation temperature was below the Ac_1 temperature, and the Zener-Hollomon parameter (Z) ranged between 10^<12>s^<-1> and 10^<16>s^<-1>. The ultrafine ferrite grains surrounded by the high angle boundaries evolved when the equivalent plastic strain exceeded the critical value of about 1. The number of newly evolved ultrafine grains increased with the strain; however, the average sizes did not depend on the strain. The grain size, d, depended on the strain rate and the deformation temperature. An equation, d(μm)=10^<2.07>Z^<-0.16>, was obtained experimentally. The details of the phenomena are compared with the dynamic discontinuous recrystallization in ferritic steels.
2002-12-01