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Kinetics of ferrite transformation in an HSLA steel containing Nb
Author(s) -
Gupta Shant P.
Publication year - 1993
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199301581
Subject(s) - ferrite (magnet) , chemistry , alloy , kinetics , thermodynamics , reaction rate constant , ternary operation , metallurgy , analytical chemistry (journal) , crystallography , materials science , composite material , physics , quantum mechanics , chromatography , computer science , programming language
An investigation was carried out to study the thickening kinetics of ferrite allotriomorph in a high‐strength low‐alloy (HSLA) steel containing Nb. Using optical microscopy to measure growth distance, it has been shown that the movement of the α/γ interface follows a parabolic relationship with the reaction time. By modelling the steel as a ternary Fe‐C‐Mn alloy, the growth rate constants, αe and αpara, were calculated assuming full equilibrium and paraequilibrium modes of transformation, respectively. The parabolic growth rate constant lies within an order of magnitude of the values for αpara up to about 1000 K with no partitioning of Mn. An abrupt decrease in the rate of growth of ferrite has been observed at higher temperatures. The parabolic growth rate constant at the highest temperature (1062 K) is about an order of magnitude higher than the value of αe indicating that equilibrium partitioning of Mn has occurred. Thus a change from no partitioning at lower temperatures to partial or full partitioning of Mn at higher temperatures describes the kinetics of ferrite transformation in this steel.