In-situ observation of tensile deformation and retained austenite transformation behaviors in carbide-free bainitic steel

摘要

Carbide-free bainitic steel is widely manufactured and applied due to its excellent mechanical properties. In this work, its microstructural evolution and retained austenite transformation behaviors during tensile deformation were studied through in-situ scanning electron microscopy, transmission electron microscopy, and electron-backscattered diffraction. Results indicated that the high plasticity of carbide-free bainitic steel under tensile load was closely related to the rotation, bending, and elongation of bainitic sheaves because these mechanical responses delayed crack initiation and propagation. The mechanical stability of blocky retained austenite was considerably affected by the crystallographic orientation of bainitic sheaves. The blocks of retained austenite adjacent to the bainitic sheaves with high Schmid factors were easier to transform into martensite than those near the bainitic sheaves with low Schmid factors.