Interaction of carbon partitioning, carbide precipitation and bainite formation during the Q&P process in a low C steel
F Hajy Akbary (TU Delft - (OLD) MSE-3, Material Innovation Institute (M2i))
J Sietsma (TU Delft - (OLD) MSE-3)
G Miyamoto (Tohoku University)
T Furuhara (Tohoku University)
MJ Santofimia (TU Delft - (OLD) MSE-3)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
Theoretical understanding of the “quenching and partitioning” (Q&P) process allowed developing microstructures consisting of carbon-depleted martensite and retained austenite that deliver superior mechanical properties. Most of the models describing the Q&P process are limited to systems in which carbide precipitation in martensite and decomposition of austenite to bainite are totally suppressed. However, these reactions are often unavoidable, even in low-carbon steels containing a relatively high concentration of Si and Mn. This work investigates interactions between carbon partitioning, carbide precipitation and carbide-free bainite formation during the Q&P process of a 0.3C–1.6Si–3.5Mn (wt.%) steel with non-homogenous distribution of the alloying elements. It was found that prior to the partitioning step ɛ-carbide forms in martensite. The decomposition of this carbide is required for a full completion of the carbon partitioning from martensite to austenite. Slow kinetics of decomposition of ɛ-carbide retards the carbon partitioning process. Results show that a fraction of austenite becomes stable by carbon partitioning and does not decompose to bainite. In the specimens quenched to lower temperature, a higher fraction of austenite becomes stable and consequently a lower fraction of bainite is formed.