Koh-ichi Sugimoto1, Tsuneaki Sakaki2, Mitsuyuki Kobayashi3 and Shin-ichi Yasuki4
1Department of Functional Machinery and Mechanics, Faculty of Textile Science and Technology, Shinshu University, Ueda
The Bauschinger effect behavior and the influences of retained austenite on that of 0.1~0.4%C-1.5%Si-1.5%Mn in mass% TRIP (Transformation-Induced Plasticity)-aided dual-phase steels containing the retained austenite of 6 to 20 vol% were measured, and the relations between the Bauschinger stress and mean internal stress calculated on the basis of a continuum theory were investigated.
The Bauschinger effects in TRIP-aided dual-phase steels were characterized by remarkable transitional-softening and subsequent permanent-softening proposed by Orowan, the amounts of which were relatively small compared to ones of conventional ferrite-martensite dual-phase steels. Retained austenite was found to make the Bauschinger effect small, although strain-induced transformation of retained austenite to martensite, which was particularly promoted during deformation in tension, enhanced a strain hardening rate and flow stress in tension.
The Bauschinger effect and the Bauschinger stress were found to be controlled by a long range internal stress arising from unrelaxed plastic strain between the matrix and the second phase islands. The internal stress was estimated from continuum theory considering the effects of strain-induced transformation and plastic relaxation during straining.
Bauschinger effect, Bauschinger stress, transformation-induced plasticity, strain-induced transformation, dual-phase steel, retained austenite, internal stress, continuum theory
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