An in situ powder neutron diffraction study of nano-precipitate formation during processing of oxide-dispersion-strengthened ferritic steels

Zhang, Hongtao; Gorley, Michael; Chong, Kok Boon; Fitzpatrick, Michael E.; Roberts, Steve; Grant, Patrick S.

doi:10.1016/j.jallcom.2013.08.069

Cited by 25 publications

(12 citation statements)

References 28 publications

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“…The powder mixture was mechanically alloyed in 99.999% purity Ar using a planetary mill (Pulverisette 6, Fritsch GmbH, Germany) with a chrome-steel bowl (500 ml) and AISI 52100 steel balls (800 g, 10 mm diameter) with a ball-to-powder weight ratio of 10:1 and a rotational speed of 150 rpm. A steady-state condition/microstructure of the 14YT powder was achieved after 60 h [33]. The 14YT powder was loaded into a graphite mould lined with graphite paper in an Ar-filled glove box for SPS consolidation.…”

Section: Powder Processing By Ma and Spsmentioning

confidence: 99%

Processing and microstructure characterisation of oxide dispersion strengthened Fe–14Cr–0.4Ti–0.25Y2O3 ferritic steels fabricated by spark plasma sintering

Zhang

Huang

Ning

et al. 2015

Journal of Nuclear Materials

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h i g h l i g h t sNanostructured ODS steels were successfully produced by SPS. Presence of Y 2 Ti 2 O 7 nanoclusters was confirmed by synchrotron XRD and microscopy. The chemistry of nanoclusters tested by ATP indicated they are Y-Ti-O oxides. a b s t r a c tFerritic steels strengthened with Ti-Y-O nanoclusters are leading candidates for fission and fusion reactor components. A Fe-14Cr-0.4Ti + 0.25Y 2 O 3 (14YT) alloy was fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). The densification of the 14YT alloys significantly improved with an increase in the sintering temperature. Scanning electron microscopy and electron backscatter diffraction revealed that 14YT SPS-sintered at 1150°C under 50 MPa for 5 min had a high density (99.6%), a random grain orientation and a bimodal grain size distribution (<500 nm and 1-20 lm). Synchrotron X-ray diffraction patterns showed bcc ferrite, Y 2 Ti 2 O 7 , FeO, and chromium carbides, while transmission electron microscopy and atom probe tomography showed uniformly dispersed Y 2 Ti 2 O 7 nanoclusters of <5 nm diameter and number density of 1.04 Â 10 23 m À3 . Due to the very much shorter consolidation times and lower pressures used in SPS compared with the more usual hot isostatic pressing routes, SPS is shown to be a cost-effective technique for oxide dispersion strengthened (ODS) alloy manufacturing with microstructural features consistent with the best-performing ODS alloys.

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Section: Powder Processing By Ma and Spsmentioning

confidence: 99%

Processing and microstructure characterisation of oxide dispersion strengthened Fe–14Cr–0.4Ti–0.25Y2O3 ferritic steels fabricated by spark plasma sintering

Zhang

Huang

Ning

et al. 2015

Journal of Nuclear Materials

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“…This can be explained by the ferritestabilizing effect of both titanium and oxygen added in the ODS powder compared to the two others. Formation of low fraction of austenite was observed by neutron in situ study by Zhang et al [31]. Concerning the hardness plateau observed in the atomized powder, it can be assumed that the formation of austenite and further martensite during cooling can harden the material sufficiently to compensate the strength loss due to significant grain growth.…”

Section: Microstructure Of Consolidated Materialsmentioning

confidence: 93%

“…The bimodal microstructure may result from heterogenous secondary recrystallization of some grains at the expense of others. This could be due to strain-induced boundary migration due to heterogenous plastic deformation upon milling process, combined with preferential pinning of some grain boundaries by fine and dense particles [23,31]. Regardless, the influence of such heterogenous microstructure on the mechanical properties is not straightforward, since the contribution of grain size mostly deviates from classic HallePetch hardening [32].…”

Section: Introductionmentioning

confidence: 99%

Tailoring the microstructure and the mechanical properties of ultrafine grained high strength ferritic steels by powder metallurgy

Mouawad

Boulnat

Fabrègue

et al. 2015

Journal of Nuclear Materials

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“…Recent studies by neutron diffraction have suggested that Y and O dissolution occurs during mechanical milling. [32] Atom probe studies indicated formation of approximately 2 nm sized atomic clusters consisting of Y, Ti, and O atoms. [33] The cluster formation has been reported to occur due to the enhanced diffusivity aided by large number of vacancies and the relative chemical affinities of O, Ti, and Y.…”

Section: A Milled Powdersmentioning

confidence: 99%

Effect of Process Parameters on Microstructure and Hardness of Oxide Dispersion Strengthened 18Cr Ferritic Steel

Nagini

Vijay

Rajulapati

et al. 2016

Metall Mater Trans A

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Pre-alloyed ferritic 18Cr steel (Fe-18Cr-2.3W-0.3Ti) powder was milled with and without nano-yttria in high-energy ball mill for varying times until steady-state is reached. The milled powders were consolidated by upset forging followed by hot extrusion. Microstructural changes were examined at all stages of processing (milling, upset forging, and extrusion). In milled powders, crystallite size decreases and hardness increases with increasing milling time reaching a steady-state beyond 5 hours. The size of Y 2 O 3 particles in powders decreases with milling time and under steady-state milling conditions; the particles either dissolve in matrix or form atomic clusters. Upset forged sample consists of unrecrystallized grain structure with few pockets of fine recrystallized grains and dispersoids of 2 to 4 nm. In extruded and annealed rods, the particles are of cuboidal Y 2 Ti 2 O 7 at all sizes and their size decreased from 15 nm to 5 nm along with significant increase in number density. The oxide particles in ODS6 are of cuboidal Y 2 Ti 2 O 7 with diamond cubic crystal structure (Fd 3m) having a lattice parameter of 10.1 Å and are semicoherent with the matrix. The hardness values of extruded and annealed samples predicted by linear summation model compare well with measured values.

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An in situ powder neutron diffraction study of nano-precipitate formation during processing of oxide-dispersion-strengthened ferritic steels

Cited by 25 publications

References 28 publications

Processing and microstructure characterisation of oxide dispersion strengthened Fe–14Cr–0.4Ti–0.25Y2O3 ferritic steels fabricated by spark plasma sintering

Processing and microstructure characterisation of oxide dispersion strengthened Fe–14Cr–0.4Ti–0.25Y2O3 ferritic steels fabricated by spark plasma sintering

Tailoring the microstructure and the mechanical properties of ultrafine grained high strength ferritic steels by powder metallurgy

Effect of Process Parameters on Microstructure and Hardness of Oxide Dispersion Strengthened 18Cr Ferritic Steel

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