Precipitation behavior in G-phase strengthened ferritic stainless steels

Mujin Yang, Daniel J.M. King, Ivan Postugar, Yuren Wen, Junhua Luan, Bernd Kuhn, Zengbao Jiao, Cuiping Wang, M. R. Wenman, Xingjun Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

4 Citations (Scopus)

Abstract

A series of G-phase strengthened ferritic stainless steels Fe-20Cr-3Ni-3Si-X (X = 2Mn, 1Mn-2Ti, 1Mn-2Nb and 1Mn-2Ta) are characterized after aging using experimental (microhardness, TEM and APT) and theoretical (DFT) techniques. The results indicate that the Ni16Mn6Si7 G-phase shows sluggish precipitation during aging treatment. This was attributed to the small difference in the enthalpy of formation between the Ni16Mn6Si7 G- and BCC phase and the requirement of high Ni:Fe ratio. A superfine Ni16Ti6Si7 G-phase was found to precipitate as a core accompanied with an “envelope” of Fe2TiSi-L21 Heusler phase during early aging (≤24 h) in the Ti containing alloy. This morphology is predicted to occur due to early Ni clustering in ferrite and a negative Ni concentration gradient away from the cluster that favors Fe2TiSi formation. The G-phases show only particle coarsening without obvious chemical composition evolution for further aging up to 96 h. A prominent hardness increase of 100-275 HV was also observed during aging. These findings provide valuable insight into methods for precipitating low lattice mismatch silicide phases for the development of future high strength steels.

Original languageEnglish
Article number116542
JournalActa Materialia
Volume205
DOIs
Publication statusPublished - 15 Feb 2021

Keywords

  • Aging hardening
  • Atom probe tomography
  • Ferritic stainless steel
  • G-phase
  • Nano-precipitation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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