발간논문

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Vol.27, No.10, 930 ~ 939, 1989
Title
Consideration on Bainitic Transformation mechanism of steel
최종술Chong Sool Choi, 최점용Jeom Yong Choi, 손영일Young Ill Son, 손인진In Jin Shon, 문인기In Ge Moon
Abstract
In order to establish bainitic transformation mechanism of steel, low carbon-Ni-Cr-Mo steel was used as at. experimental alloy. Transformation-time curve in upper bainite of the steel showed S-shaped curve indicating diffusional transformation of nucleation and growth, while transformation time curve in lower bainite showed C-shaped curve often appearing in isothermal martensitic transformation. Furthermore, the bainitic trans formation rate showed negative dependence on temperature and the degree of the negative dependence was greater in the lower bainite than in the upper bainite. It was concluded by these results that the lower bainite was produced by shear transformation and that the upper bainite was formed by shear and diffusional transformations. A new mechanism to explain how the lower bainite is formed martensitically at temperatures above Ms temperature has been proposed on the basis of carbon concentration fluctuation model. The width of ferrite lath in the lower bainite was decreased and the bainte finishing time was shorter with increasing deformation degree of metastable austenite in bainitic bay. These experimental results well supported the proposed bainite transformation mechanism.
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