Vacancies as a constitutive element for the design of nanocluster-strengthened ferritic steels

Abstract

The existence of nanoclusters that are thermodynamically stable at elevated temperatures is truly intriguing because of its scientific implications and potential applications. Highly stable nanoclusters have been observed by atom probe tomography in iron-based alloys at temperatures close to 1400°C (0.92T_m) that appear to defy the stability constraints of artificially created nanostructured materials. The ∼4-nm-diameter Ti-, Y- and O-enriched nanoclusters are identified in the new form of a highly defective material state with vacancies as the critical alloying component and with (Ti + Y):O ratio different from the stable TiO₂ and Y₂Ti₂O₇ oxides. Vacancies play an indispensable role in enhancing the oxygen solubility and increasing the oxygen binding energy in the presence of Ti and Y, resulting in the stabilization of coherent nanoclusters. Atom probe tomography characterizations and theoretical predictions indicate that vacancies can be exploited for the first time as a nanoscale constituent to design materials with far superior high temperature properties.

Keywords

nanocluster / vacancy / ferritic alloy / nanoscale constituent / high temperature property

References

[1] MillerM K. Atom Probe Tomography: Analysis at the Atomic Level. Kluwer Academic/Plenum Publishers, 2000

[2] LarsonD J, MaziaszP J, KimI-S, . Three-dimensional atom probe observation of nanoscale titanium-oxygen clustering in an oxide-dispersion-strengthened Fe-12Cr-3W-0.4Ti + Y₂O₃ ferritic alloy. Scripta Materialia, 2001, 44(2): 359–364

[3] MillerM K, KenikE A, RussellK F, . Atom probe tomography of nanoscale particles in ODS ferritic alloys. Materials Science and Engineering: A, 2003, 353(1–2): 140–145

[4] MillerM K, HoelzerD T, KenikE A, . Nanometer scale precipitation in ferritic MA/ODS alloy MA957. Journal of Nuclear Materials, 2004, 329–333(Part 1): 338–341

[5] MillerM K, HoelzerD T, KenikE A, . Stability of ferritic MA/ODS alloys at high temperatures. Intermetallics, 2005, 13(3–4): 387–392

[6] MillerM K, RussellK F, HoelzerD T. Characterization of precipitates in MA/ODS ferritic alloys. Journal of Nuclear Materials, 2006, 351(1–3): 261–268

[7] HoelzerD T, BentleyJ, SokolovM A, . Influence of particle dispersions on the high-temperature strength of ferritic alloys. Journal of Nuclear Materials, 2007, 367–370(Part 1): 166–172

[8] PareigeP, MillerM K, StollerR E, . Stability of nanometer-sized oxide clusters in mechanically-alloyed steel under ion-induced displacement cascade damage conditions. Journal of Nuclear Materials, 2007, 360(2): 136–142

[9] AllenT R, GanJ, ColeJ I, . Radiation response of a 9 chromium oxide dispersion strengthened steel to heavy ion irradiation. Journal of Nuclear Materials, 2008, 375(1): 26–37

[10] MillerM K, SmithG D W. Atom Probe Microanalysis: Principles and Applications to Materials Problems (in Chinese, trans. Gong Y H, Sha W).Beijing: Peking University Press, 1993 (Original work published. Pittsburgh, PA: Materials Research Society, 1989)

[11] FuC L, KrcmarM, PainterG S, . Vacancy mechanism of high oxygen solubility and nucleation of stable oxygen-enriched clusters in Fe. Physical Review Letters, 2007, 99: 225502

[12] PerdewJ P, WangY. Accurate and simple analytic representation of the electron-gas correlation energy. Physical Review B, 1992, 45: 13244–13249

[13] VanderbiltD. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. Physical Review B, 1990, 41: 7892–7895

[14] KresseG, FurthmüllerJ. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 1996, 6(1): 15–50

Acknowledgements

This research was sponsored by the U. S. Department of Energy: Division of Materials Sciences and Engineering (MKM, CLF, MK, DTH and CTL); and research at the Oak Ridge National Laboratory SHaRE User Facility was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy (MKM).

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