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Title: A study of damage clusters produced by heavy-ion irradiation of nickel and its alloys
Author: Robinson, Thomas Martin
ISNI:       0000 0004 2667 7992
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1978
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The damage clusters produced by low dose, 80 keV Ni+ and W+ heavy-ion bombardment of pure nickel; of two nichrome alloys (with 8% and 17%Cr); and of a ternary alloy and 321 stainless steel which have the same base composition (Fe/Ni10%/Cr17%) have been studied by means of transmission electron microscopy. In all cases where the defects could be identified with confidence they were found to be vacancy in nature. Most of the defects were identified as Frank loops, some of which had partially dissociated. The number of loops that were identified as dissociated and the average degree of dissociation were dependent on the stacking fault energy γ, being greater in the low-γ ternary alloy and the stainless steel than in the high-γ nickel and nichrome alloys. In the high-y materials a small proportion (< 5%) of perfect loops was also observed. Defect yield values were between a factor of 2 and 5 higher for W+ ion bombardment than for the corresponding Ni+ ion irradiations, but the effect on the mean defect size and cascade efficiency was much less pronounced. In the case of the Ni+ ion bombardment, the defect yields in the two nichrome alloys were lower than in pure Ni. No such effect was observed for the W+ ion irradiations, when defect yield and cascade efficiency values very similar to those of pure nickel were obtained. The defect yield in the W+ ion irradiated ternary alloy was considerbly smaller than in the nichrome alloys and there was a further major decrease in the stainless steel. These reductions in defect yields were not accompanied by a change in the mean defect size nor in the distribution of the defect sizes which were very similar in all the materials for irradiation by a given ion species. The defect yield in W+ ion irradiated Ni remained constant with increasing irradiation temperature up to ~450°C and then decreased sharply at higher irradiation temperatures. The defect yield in W+ ion irradiated Ni/Cr17% remained constant up to at least 500°C. Possible physical explanations for these results are discussed.
Supervisor: Whelan, M. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Nickel ; Nickel alloys ; Metals ; Irradiation ; Heavy ions