An approach to define the effective lath size controlling yield strength of bainite

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 527; no. 24; pp. 6614 - 6619
• Main Authors: Zhu, Kangying, Bouaziz, Olivier, Oberbillig, Carla, Huang, Mingxin
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 2010; Elsevier
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Elasticity. Plasticity; Electron backscattering diffraction (EBSD); Engineering Sciences; Exact sciences and technology; Lath misorientation; Lath size; Materials; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Ultra-low carbon bainitic steels; Yield stress; Ultra-low carbon bainitic steels; Lath misorientation; Electron backscattering diffraction (EBSD); Yield stress; Lath size; Plastic flow; Very low carbon steel; Heat treatments; EBSD; Dislocations; Bainitic steel; Yield strength; Property structure relationship; Microstructure; Flow stress
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2010.06.061

In this study, we developed a series of fully bainitic microstructures with negligible carbide precipitation in ultra-low carbon steels. Then, we investigated the microstructure by EBSD as well as their mechanical properties. It is found that the yield stress of such bainite is proportional to the inverse lath size defined with low boundary misorientation (2–7°). We explained this by employing a theory which predicts the flow stress of deformed metals, assuming that both lath boundary and dislocation cell boundary have similar capability of being dislocation obstacles. A fully bainitic microstructure with negligible carbide precipitation is obtained in two ultra-low carbon steels. The size and misorientation of bainite laths are analysed by Electron Back Scattering Diffraction (EBSD). It is found that the yield stress of bainite is proportional to the inverse lath size defined with low boundary misorientation (2–7°). This can be explained by a theory predicting the flow stress of deformed metals, assuming that both lath boundary and dislocation cell boundary have similar capability of being dislocation obstacles.