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Bainite morphologies in a 0.2 C–1.5 Mn steel
Author(s) -
Joarder Asok,
Sarma Darbha Subrahmanya
Publication year - 1992
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199200467
Subject(s) - bainite , lath , isothermal transformation diagram , austenite , ferrite (magnet) , metallurgy , materials science , martensite , pearlite , isothermal process , microstructure , alloy steel , alloy , transmission electron microscopy , composite material , nanotechnology , thermodynamics , physics
The isothermal transformation products of austenite over a wide range of temperatures and times in the bainitic range in a 0.2 wt.% C–1.5 wt.% Mn steel have been studied by transmission electron microscopy in order to characterise the bainitic microstructures in low‐carbon low‐alloy steels. Widmanstätten ferrite has formed with alternate layers of austenite (martensite) as a transition product at 600 and 500°C that has finally transformed on further isothermal transformation to either pearlite (at 600°C) or upper bainite (at 500°C). This type of transformation product was referred to as BI bainite by earlier investigators, but on the basis of the present investigation it is concluded that such ferrite‐austenite (martensite) structures are not bainitic as this is not the final transformation product either at 600 or 500°C. Both upper bainite and lath‐type lower bainite are formed at 450°C while the transformation product has been only lath‐type lower bainite at 400°C.