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You searched for subject:(Proton irradiatied layer). One record found.

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University of Oxford

1. Jones, Christopher A. A micromechanical investigation of proton irradiated oxide dispersion strengthened steels.

Degree: PhD, 2016, University of Oxford

This thesis was most concerned with the mechanical response to irradiation of two in-house produced oxide dispersion strengthened (ODS) steels and two non-ODS coun- terparts. The steels, manufactured by Dr. M. J. Gorley (University of Oxford), were me- chanically alloyed from gas-atomised Fe-14Cr-3W-0.2Ti, with the addition of 0.25Y2O3 powder in the case of the ODS variants. The powders were hot isostatic pressed at consolidation temperatures of 950 °C and 1150 °C. The four steels were designated 14WT 950 (non-ODS), 14YWT 950 (ODS), 14WT 1150 (non-ODS) and 14YWT 1150 (ODS), and were used in the as-produced condition. Initially, the macroscale elastic modulus and yield stress were determined using a four-point flexure test, employing digital image correlation (DIC) as a strain gauge. The microcantilever size eects were then characterised, and it was determined that the yield stress signicantly diverged from macroscale values at microcantilever beam depths of < 4.5 μm. Using knowledge of this, the in-house produced alloys were irradiated with 2 MeV protons at the Surrey Ion Beam Centre (University of Surrey, UK) to a displacement damage of ∼ 0.02 dpa and 0.2 dpa (Bragg peak). This was to produce a deep irradiated layer for the fabrication of large microcantilevers with reduced size effects. The cross-sectional surface of the irradiated layer was then exposed and inclined linear arrays of 250 nm deep indents were placed across the damage prole. 14WT 1150 (non-ODS) revealed a clear proton damage prole in plots of hardness against irradiation depth, 14WT 950 (non-ODS) also showed modest hardening in the region of the Bragg peak. No appreciable hardening was observed in either 14YWT specimens, attributed to the fine dispersion of nanoscale oxides providing a high number density of defect sink sites. However, a large bimodal variation in hardness was measured in both ODS variants. This was investigated using EBSD and EDX, and was determined to be caused by a pronounced heterogeneity of the microstructure. While Hall-Petch strengthening and changes in the local chemistry had some effect on the measured hardness, the most likely cause of the large variation in local hardness was heterogeneity in the nanoscale oxide population. Microcantilevers were fabricated out of the irradiated layer cross-section in 14WT 1150 and 14YWT 1150. Larger microcantilevers, with ∼ 5 μm beam depth, were placed with their beam centre at ∼ 0.026 dpa. Smaller microcantilevers, with ∼ 1.5 μm beam depth, were placed with their beam centre at the Bragg peak, 0.2 dpa. Both the large and the small microcantilevers fabricated in 14WT 1150 (non-ODS) displayed significant irradiation hardening. In the ODS variant, 14YWT 1150, irradiation hardening appeared to be reduced. The work in this thesis successfully showed that it was possible to extract a close approximation of the macroscale yield stress from shallow irradiated layers, providing that the irradiation condition is carefully chosen in…

Subjects/Keywords: 620.1; Micromechanical examination of irradiated layers; Micromecanical testing methods; Lengthscale-dependent crystal plasticity; Micromechanical size effect; Four-point flexure testing; Micromechanical size efffect; Microcantilever; ODS steels; Microcantilever size effect; Proton irradiation; Oxide dispersion strengthened steels; Proton irradiatied layer; Crystal plasticity; Nanoindentation; Four-point bend testing

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Jones, C. A. (2016). A micromechanical investigation of proton irradiated oxide dispersion strengthened steels. (Doctoral Dissertation). University of Oxford. Retrieved from http://ora.ox.ac.uk/objects/uuid:fadd9abf-b5d0-4ea1-9d86-50628ec0476a ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.748672

Chicago Manual of Style (16th Edition):

Jones, Christopher A. “A micromechanical investigation of proton irradiated oxide dispersion strengthened steels.” 2016. Doctoral Dissertation, University of Oxford. Accessed November 26, 2020. http://ora.ox.ac.uk/objects/uuid:fadd9abf-b5d0-4ea1-9d86-50628ec0476a ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.748672.

MLA Handbook (7th Edition):

Jones, Christopher A. “A micromechanical investigation of proton irradiated oxide dispersion strengthened steels.” 2016. Web. 26 Nov 2020.

Vancouver:

Jones CA. A micromechanical investigation of proton irradiated oxide dispersion strengthened steels. [Internet] [Doctoral dissertation]. University of Oxford; 2016. [cited 2020 Nov 26]. Available from: http://ora.ox.ac.uk/objects/uuid:fadd9abf-b5d0-4ea1-9d86-50628ec0476a ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.748672.

Council of Science Editors:

Jones CA. A micromechanical investigation of proton irradiated oxide dispersion strengthened steels. [Doctoral Dissertation]. University of Oxford; 2016. Available from: http://ora.ox.ac.uk/objects/uuid:fadd9abf-b5d0-4ea1-9d86-50628ec0476a ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.748672

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