TY - JOUR
T1 - Effect of impurities on phase transformation and precipitation in a low-carbon steel
AU - Duan, Jiaqi
AU - Farrugia, Didier
AU - Poplawsky, Jonathan D.
AU - Davis, Claire
AU - Li, Zushu
N1 - Publisher Copyright:
© 2024 The Author(s)
PY - 2024/8
Y1 - 2024/8
N2 - Impurity elements have been added to a commercial low carbon steel grade to simulate the levels that could arise as a result of increased scrap recycling during steel production. In this study, continuous cooling transformation (CCT) diagrams were constructed for the steels with varying levels of impurities, and it is shown that impurities suppress the phase transformation across a wide range of cooling rates. It was found that a step was formed in the start temperature curve, separating the reconstructive and displacive transformations. The influence of impurities on both the reconstructive transformation and displacive transformation are discussed. Additionally, Cu precipitates were observed using scanning transmission electron microscopy (STEM) in the highest impurity-containing steel after slow cooling (0.05°C/s), fast cooling (5°C/s) and interrupted cooling. It was found that the precipitation kinetics is in the following order: cementite within the secondary phase and cementite at secondary phase-ferrite interface> ferrite grain boundaries> ferrite grain matrix. Atom-probe tomography (APT) revealed Cu precipitates formed on the surface of cementite lamellae, but not within it. This work offers insights for the phase transformation control and precipitation regulation during the thermomechanical processing of low carbon steels containing impurity elements due to scrap recycling.
AB - Impurity elements have been added to a commercial low carbon steel grade to simulate the levels that could arise as a result of increased scrap recycling during steel production. In this study, continuous cooling transformation (CCT) diagrams were constructed for the steels with varying levels of impurities, and it is shown that impurities suppress the phase transformation across a wide range of cooling rates. It was found that a step was formed in the start temperature curve, separating the reconstructive and displacive transformations. The influence of impurities on both the reconstructive transformation and displacive transformation are discussed. Additionally, Cu precipitates were observed using scanning transmission electron microscopy (STEM) in the highest impurity-containing steel after slow cooling (0.05°C/s), fast cooling (5°C/s) and interrupted cooling. It was found that the precipitation kinetics is in the following order: cementite within the secondary phase and cementite at secondary phase-ferrite interface> ferrite grain boundaries> ferrite grain matrix. Atom-probe tomography (APT) revealed Cu precipitates formed on the surface of cementite lamellae, but not within it. This work offers insights for the phase transformation control and precipitation regulation during the thermomechanical processing of low carbon steels containing impurity elements due to scrap recycling.
KW - APT
KW - Low carbon steel
KW - Phase transformation
KW - Precipitation
KW - Scrap
UR - http://www.scopus.com/inward/record.url?scp=85195308869&partnerID=8YFLogxK
U2 - 10.1016/j.mtla.2024.102141
DO - 10.1016/j.mtla.2024.102141
M3 - Article
AN - SCOPUS:85195308869
SN - 2589-1529
VL - 36
JO - Materialia
JF - Materialia
M1 - 102141
ER -