Koh-ichi Sugimoto1, Mitsuyuki Kobayashi2,Shin-ichi Yasuki1 and Shun-ichi Hashimoto3
1Department of Functional Machinery and Mechanics, Shinshu University, Ueda
The influence of deformation temperature on the Bauschinger effect (BE) of a high-strength TRIP-aided dual-phase (TDP) steel containing retained austenite particles of 10 vol% was investigated in a temperature range between 27 and 200°C.
The BE of the TDP steel depended significantly on the deformation temperature, although such a temperature dependence did not appear in a conventional ferrite-martensite dual-phase (DP) steel. Large BE, i.e., remarkable transitional-softening and subsequent permanent-softening proposed by Orowan, appeared at 100 and 200°C, at which the retained austenite particles are more resistant to the strain-induced α′ transformation (SIT) than those at 27°C. The Bauschinger stress obtained at 200°C was as high as that of the DP steel.
The retained austenite particles as a hard phase increased the Bauschinger stress. The SIT, however, was expected to lower the Bauschinger stress by the following reason. An expansion and shear deformation resulting from the SIT reduce both internal stresses in retained austenite islands and in the ferrite matrix.
(Received November 24, 1993)
Bauschinger effect, dual-phase steel, high strength steel, retained austenite, austenite stability, internal stress, transformation induced plasticity, strain-induced transformation
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