Influence of Si on the microstructure and C redistribution in martensitic steels

• Published in: Materials & design Vol. 229; p. 111875
• Main Authors: Seehaus, Mattis, Korte-Kerzel, Sandra, Sandlöbes-Haut, Stefanie
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2023; Elsevier
• Subjects: Atom probe tomography; Carbon segregation; Martensite/austenite interface; Martensitic steel; Orientation relationship; Orientation relationship; Martensitic steel; Carbon segregation; Martensite/austenite interface; Atom probe tomography
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2023.111875

[Display omitted] •Silicon addition in Fe-Ni-C alloys leads to smaller initial austenite grains and less retained austenite.•c/a ratio is not significantly impacted by Silicon addition.•Identification of the Greninger Troiano orientation relationship for Fe-Ni-C-(Si)•Si affects the C segregation and partitioning behaviour in the vicinity of the phase interface.•Combined atom probe tomography and transmission electron microscopy reveal carbon clustering along twins in the martensite. In martensitic steels the distribution of C is fundamental for the technological material properties. However, the effect of Si on C segregation is not known in detail. In this study, the impact of Si on the microstructure of martensitic steels is investigated using scanning electron microscopy and the martensite/austenite orientation relationships are determined using electron backscatter diffraction and transmission Kikuchi diffraction. Transmission electron microscopy and selected area diffraction pattern analysis were used to analyse the intragranular substructure of the martensitic phase. Further, the effect of Si on the redistribution of C is investigated by atom probe tomography in combination with transmission Kikuchi diffraction measurements in order to obtain the local C distribution and correlate it with the crystallography. It was found that the Si addition forms a sigmoidal distribution at the phase boundary and functions as a barrier for C segregation, hence reduces C partitioning into the austenite, while a Si free alloy shows clear C partitioning. Further it was observed that stable C cluster formation occurs along fine twin boundaries in the martensite, inhibiting carbide formation and partitioning of the C into the austenite.