Study on the Strain Hardening Behaviors of TWIP/TRIP Steels
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TRODUCTION
USUALLY, metals deform plastically by the gliding of dislocations in crystals.[1–4] Strengthened by deformation twinning[5] and martensitic transformation,[6] twinning-induced plasticity (TWIP) steels and transformation-induced plasticity (TRIP) steels with the combination of high strength and ductility have attracted great attention. Therefore, the deformation mechanisms including dislocation glide, deformation twinning and martensitic transformation of TWIP/TRIP steels become an area of intense investigation. It is worth noticing that the deformation mechanisms in TWIP/ TRIP steels are significantly interdependent.[7] The mechanical properties and strain hardening behaviors of steels can be regarded as the results of a competition between different deformation mechanisms governed by the stacking fault energy (SFE).[8–13] On the one hand, tremendous efforts have been placed on the determination of SFE.[14–19] Experimentally, SFE can be estimated using transmission electron microscopic
T.T. HUANG, W.J. DAN, and W.G. ZHANG are with the Department of Engineering Mechanics and Innovation Center for Advanced Ship and Deep-Sea Exploration, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China. Contact e-mail: [email protected] Manuscript submitted February 26, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
(TEM),[14,15] X-ray diffraction (XRD),[16,17] and neutron diffraction (ND).[18,19] However, the statistics coming from experimental methods are restricted to the resolution and preparation process of samples. Specially, the values of SFE determined by XRD method are poor because of the oversimplified assumptions made in the evaluation process; the TEM method strictly relies on the early stages of deformation; the application of ND needs strong neutron source and requires long time to collect data. To address this issue, Hirth[20] originally established a thermodynamic relation to calculate SFE, which was later popularized by Olson and Cohen.[12] Varied by experimental results, the thermodynamic model of SFE was further modified[21,22] and widely employed[22,23] to evaluate the effects of SFE on the deformation mechanisms of austenitic steels. The relevant factors determining SFE are revealed to be the deformation temperature[24–30] and the chemical compositions[9,14,31–47] of material. One the other hand, numerous researches have been done to establish microscopic models in order to reveal the deformation process of TWIP and TRIP steels, respectively. With the attempt to explore the mechanism of TWIP effect, the dislocation theory-based model focusing on the strain hardening behaviors of TWIP steels[48–51] and the visco-plastic self-consistent model considering texture evolution[52–56] are built. Corresponding thermodynamic model[57–63] is also developed to investigate the mechanism of TRIP effect. However, in the classical thermodynamic model of SFE mentioned above, the effect of temperature rise
resulting from deformation is neglect
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