Three-dimensional morphology and crystallographic characteristics of the low-temperature bainitic microstructure in high-carbon steel

Abstract

The three-dimensional morphology of low-temperature bainite in high-carbon steel was reconstructed by serial sectioning and computer-aided three-dimensional reconstruction techniques. Combined with laser scanning confocal microscope and electron backscatter diffraction analysis, the microstructural evolution and crystallographic orientation of low-temperature bainite were studied. The results show that the three-dimensional morphology of the low-temperature bainite sheaves is a plate-like structure. During the isothermal transformation, some new bainite plates stop growing after impinging on preformed bainite plates. However, some new bainite plates resume growth on the opposite surface of the impingement zone after briefly stopping. This is attributed to the accumulation of strain energy in the collision zone caused by impingement between bainite plates, which provides the driving force for new nucleation, thus stimulating new nucleation on the opposite surface of the collision zone. The bainite formed on the opposite surface maintains the same crystallographic orientation as the “twinned bainite”. Finally, the bainite plates form interlocked microstructures in the prior austenite grains via impingement, nucleation, and intersection.