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Title: Micro-mechanics of irradiated Fe-Cr alloys for fusion reactors
Author: Hardie, Christopher David
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2013
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In the absence of a fusion neutron source, research on the structural integrity of materials in the fusion environment relies on current fission data and simulation methods. Through investigation of the Fe-Cr system, this detailed study explores the challenges and limitations in the use of currently available radiation sources for fusion materials research. An investigation of ion-irradiated Fe12%Cr using nanoindentation with a cube corner, Berkovich and spherical tip, and micro-cantilever testing with two different geometries, highlighted that the measurement of irradiation hardening was largely dependent on the type of test used. Selected methods were used for the comparison of Fe6%Cr irradiated by ions and neutrons to a dose of 1.7dpa at a temperature of 288°C. Micro-cantilever tests of the Fe6%Cr alloy with beam depths of 400 to 7000nm, identified that size effects may significantly obscure irradiation hardening and that these effects are dependent on radiation conditions. Irradiation hardening in the neutron-irradiated alloy was approximately double that of the ion-irradiated alloy and exhibited increased work hardening. Similar differences in hardening were observed in an Fe5%Cr alloy after ion-irradiation to a dose of 0.6dpa at 400°C and doses rates of 6 x 10-4dpa/s and 3 x 10-5dpa/s. Identified by APT, it was shown that increased irradiation hardening was likely to be caused by the enhanced segregation of Cr observed in the alloy irradiated with the lower dose rate. These observations have significant implications for future fusion materials research in terms of the simulation of fusion relevant radiation conditions and micro-mechanical testing.
Supervisor: Roberts, Steve G.; Dudarev, Sergei Sponsor: EPSRC ; CCFE
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical Sciences ; Microscopy ; Surface chemistry ; Surface analysis ; Materials Sciences ; Alloys ; Atomic scale structure and properties ; Defect analysis ; High resolution microscopy ; Metallurgy ; Metallics ; Metals and ceramics ; Physical metallurgy ; Surfaces ; Surface mechanical properties ; Surface nanoscience ; Advanced materials ; Engineering & allied sciences ; Mechanical engineering ; Solid mechanics ; micro-mechanical testing ; ion implantation ; irradiation ; neutron ; dose rate ; fe-cr alloys ; radiation defects ; radiation ; radiation damage ; displacement damage ; plasticity ; size effects ; dislocations