N. Oku, K. Asakura, J. Inoue, T. Koseki, The University of Tokyo, Tokyo, Japan
Austenite-ferrite transformation of low carbon steel was in-situ observed using laser scanning confocal microscope. Morphological developments of ferrite allotriomorphs were observed in the isothermal condition, while growth directions and growth rates of ferrite plates were studied during the continuous cooling process. EBSD analysis revealed that Kurdjumov-Sach(K-S) orientation relationship was maintained between the ferrite plates and the prior austenite, and the growth direction of plates was confirmed to be <111>bcc. The temperature dependency of growth rate of the plates in <111>bcc was well explained by Zener-Hillert model, in which the plate growth is assumed to be controlled by carbon diffusion. The mechanism of bainite formation in a high strength low alloy steel is also investigated as well.
Summary: Austenite-ferrite transformation of low carbon steel was in-situ observed using laser scanning confocal microscope. Morphological developments of ferrite allotriomorphs were observed in the isothermal condition, while growth directions and growth rates of ferrite plates were studied during the continuous cooling process. EBSD analysis revealed that Kurdjumov-Sach(K-S) orientation relationship was maintained between the ferrite plates and the prior austenite, and the growth direction of plates was confirmed to be <111>bcc. The temperature dependency of growth rate of the plates in <111>bcc was well explained by Zener-Hillert model, in which the plate growth is assumed to be controlled by carbon diffusion. The mechanism of bainite formation in a high strength low alloy steel is also investigated as well.
