| Title: | Precipitation behavior in G-phase strengthened ferritic stainless steels | Authors: | Yang, M King, DJM Postugar, I Wen, Y Luan, J Kuhn, B Jiao, Z Wang, C Wenman, MR Liu, X |
Issue Date: | 15-Feb-2021 | Source: | Acta materialia, 15 Feb. 2021, v. 205, 116542 | 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. | Keywords: | Aging hardening Atom probe tomography Ferritic stainless steel G-phase Nano-precipitation |
Publisher: | Pergamon Press | Journal: | Acta materialia | ISSN: | 1359-6454 | DOI: | 10.1016/j.actamat.2020.116542 |
| Appears in Collections: | Journal/Magazine Article |
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