Nanostructured ferritic alloys, which have complex microstructures consisting of ultrafine ferritic grains with a dispersion of stable oxide particles and nanoclusters, are promising materials for fuel cladding and structural applications in the next generation nuclear reactor. This study evaluates microstructure of friction stir welded nanostructured ferritic alloys using electron microscopy and atom probe tomography techniques. Atom probe tomography results revealed that nanoclusters are coarsened and inhomogeneously distributed in the stir zone and thermomechanically affected zone. Three hypotheses on coarsening of nanoclusters are presented. The hardness difference in different regions of friction stir weld has been explained.
McClintockDA, SokolovMA, HoelzerDT, NanstadRK: ‘Mechanical properties of irradiated ODS-EUROFER and nanocluster strengthened 14YWT’, J. Nucl. Mater., 2009, 392, 353–359.
2.
MillerMK, RussellKF and HoelzerDT: ‘Characterization of precipitates in MA/ODS ferritic alloys’, J. Nucl. Mater., 2006, 351, 261–268.
3.
KishimotoH, AlingerMJ, OdetteGR and YamamotoT: ‘TEM examination of microstructural evolution during processing of 14CrYWTi nanostructured ferritic alloys’, J. Nucl. Mater., 2004, 329, 369–371.
4.
MolianPA, YangYM and PatnaikPC: ‘Laser welding of oxide dispersion-strengthened alloy MA754’, J. Mater. Sci., 1992, 27, 2687–2694.
5.
InksonBJ and ThreadgillPL: ‘Friction welding of FeAl40 grade 3 ODS alloy’, Mater. Sci. Eng. A, 1998, A258, 313–318.
6.
AtesH, TurkerM and KurtA: ‘Effect of friction pressure on the properties of friction welded MA956 iron-based superalloy’, Mater. Des., 2007, 28, 948–953.
7.
ChenCL, TatlockGJ and JonesAR: ‘Microstructural evolution in friction stir welding of nanostructured ODS alloys’, J. Alloys Compd, 2010, 504, S460–S466.
8.
WangJ, YuanW, MishraRS and CharitI: ‘Microstructure and mechanical properties of friction stir welded oxide dispersion strengthened alloy’, J. Nucl. Mater., 2013, 432, 274–280.
9.
MathonMH, KlosekV, De CarlanY and ForestL: ‘Study of PM2000 microstructure evolution following FSW process’‘J. Nucl. Mater., 2009, 386, 475–478.
10.
NohS, KasadaR, KimuraA, ParkSHC and HiranoS: ‘Microstructure and mechanical properties of friction stir processed ODS ferritic steels’, J. Nucl. Mater., 2011, 417, 245–248.
11.
WestM, JasthiB, HosemannP and SodesettiV: ‘Friction stir welding of oxide dispersion strengthened alloy MA956’, in ‘Friction stir welding and processing VI’, Vol. 33; 2011, London, The Metals Society.
12.
LegendreF, PoissonnetS, BonnaillieP, BoulangerL and ForestL: ‘Some microstructural characterisations in a friction stir welded oxide dispersion strengthened ferritic steel alloy’, J. Nucl. Mater., 2009, 386, 537–539.
13.
HoelzerDT, UnocicKA, SokolovMA and FengZ: ‘Joining of 14YWT and F82H by friction stir welding’, J. Nucl. Mater., 2013, 442, S529–S534.
14.
GaultB, MoodyMP, CairneyJM and RingerSP: ‘Atom probe microscopy’, Vol. 160; 2012, New York, Springer.
15.
LarsonDJ, ProsaTJ, UlfigRM, GeiserBP and KellyTF: ‘Local electrode atom probe tomography: a user's guide’, Vol. 160; 2013, New York, Springer.
16.
MillerMK and ForbesRG: ‘Nanocharacterization by atom probe tomography: the local electrode atom probe’; 2014, New York, Springer.
17.
JataKV and SemiatinSL: ‘Continuous dynamic recrystallization during friction stir welding of high strength aluminum alloys’, 2000, DTIC document no. AFRL-ML-WP-TP-2003-441.
18.
ChangCI, LeeCJ and HuangJC: ‘Relationship between grain size and Zener–Holloman parameter during friction stir processing in AZ31 Mg alloys’, Scr. Mater., 2004, 51, 509–514.
19.
HassanKAA, WynneBP and PrangnellPB: Fourth International Symposium on FSW, Park City, UT, TWI, 2003.
20.
GourdetS and MontheilletF: ‘A model of continuous dynamic recrystallization’, Acta Mater., 2003, 51, 2685–2699.
21.
BelyakovA, SakaiT and KaibyshevR: ‘New grain formation during warm deformation of ferritic stainless steel’, Metall. Mater. Trans. A, 1998, 29A, 161–167.
22.
BrandesMC, KovarikL, MillerMK and MillsMJ: ‘Morphology, structure, and chemistry of nanoclusters in a mechanically alloyed nanostructured ferritic steel’, J. Mater. Sci., 2012, 47, 3913–3923.
23.
ParishCM and MillerMK: ‘Aberration-corrected X-ray spectrum imaging and fresnel contrast to differentiate nanoclusters and cavities in helium-irradiated alloy 14YWT’, Microsc. Microanal., 2014, 20, 613–626.
24.
YaoL, RingerSP, CairneyJM and MillerMK: ‘The anatomy of grain boundaries: their structure and atomic-level solute distribution’, Scr. Mater., 2013, 69, 622–625.
25.
YaoL and MillerMK: Proc. MRS Fall Meeting, Symposium EE: Advanced Materials for Nuclear Energy Technologies, Boston, MA, 2013.
26.
MillerMK and YaoL: ‘Limits of detectability for clusters and solute segregation to grain boundaries’, Curr. Opin. Solid State Mater. Sci., 2013, 17, 203–210.
27.
ParishCM, EdmondsonPD, ZhangY and MillerMK: ‘Direct observation of ion-irradiation-induced chemical mixing’, J. Nucl. Mater., 2011, 418, 106–109.
28.
MillerMK, RussellKF and HoelzerDT: ‘Characterization of precipitates in MA/ODS ferritic alloys’, J. Nucl. Mater., 2006, 351, 261–268.
29.
MurrLE, LiY, FloresRD, TrilloEA and McClureJC: ‘Intercalation vortices and related microstructural features in the friction-stir welding of dissimilar metals’, Mater. Res. Innov., 1998, 2, 150–163.
30.
HirataA, FujitaT, WenYR, SchneibelJH, LiuCT and ChenMW: ‘Atomic structure of nanoclusters in oxide-dispersion-strengthened steels’, Nat. Mater., 2011, 10, 922–926.
31.
MillerMK, HoelzerDT, KenikEA and RussellKF: ‘Stability of ferritic MA/ODS alloys at high temperatures’, Intermetallics, 2005, 13, 387–392.
32.
AllenTR, GanJ, ColeJI, MillerMK, BusbyJT, ShutthanandanS and ThevuthasanS: J. Nucl. Mater., 2008, 375, 26.
33.
SahaA and OlsonGB: ‘Computer-aided design of transformation toughened blast resistant naval hull steels: part I’, J. Computer-Aided Mater. Des., 2007, 14, 177–200.
34.
YuX, CaronJL, BabuS, LippoldJ, IsheimD and SeidmanDN: ‘Characterization of microstructural strengthening in the heat-affected zone of a blast-resistant naval steel’, Acta Mater., 2010, 58, 5596–5609.
35.
KimJH, ByunTS, HoelzerDT, ParkCH, YeomJT and HongJK: ‘Temperature dependence of strengthening mechanisms in the nanostructured ferritic alloy 14YWT: part II—mechanistic models and predictions’, Mater. Sci. Eng. A, 2013, A559, 111–118.
36.
ForemanAJE and MakinMJ: ‘Dislocation movement through random arrays of obstacles’, Philos. Mag., 1966, 14, 911–924.
37.
KocksUF: ‘Statistical treatment of penetrable obstacles’, Can. J. Phys., 1967, 45, 737–755.
38.
MishraRS and MaZY: ‘Friction stir welding and processing’, Mater. Sci. Eng. R., 2005, 50, 1–78.
