Structure-property relations in superalloy single crystals
<p>This research is concerned with a single crystal nickel-base superalloy which has been developed for application as a high pressure turbine blade material in jet aircraft engines. The microstructures and mechanical properties of superalloys, including the effects of heat-treatments, have b...
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| Format: | Thesis |
| Language: | English |
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1984
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| _version_ | 1797075235383541760 |
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| author | Hopgood, A |
| author2 | Martin, J |
| author_facet | Martin, J Hopgood, A |
| author_sort | Hopgood, A |
| collection | OXFORD |
| description | <p>This research is concerned with a single crystal nickel-base superalloy which has been developed for application as a high pressure turbine blade material in jet aircraft engines. The microstructures and mechanical properties of superalloys, including the effects of heat-treatments, have been reviewed.</p> <p>The effects of heat-treatments on the γ' precipitate distributions have been investigated. During ageing at 900°C or 800°C, the precipitates adopt an irregular, rounded and highly interconnected microstructure, indicative of precipitate coalescence, whilst at higher ageing temperatures a regular cuboidal precipitate morphology is formed. The kinetics of precipitate coarsening have been investigated, and slight deviations from the power-law predicted by a number of theoretical models were observed. These deviations have been discussed in terms of a progressive transition in the dominant coarsening mechanism.</p> <p>Constant load creep tests were carried out, and although the tensile axis was nominally parallel to [001], the degree and direction of misorientation were found to be critical to the extent of the primary creep strain. Primary creep was shown to proceed by slip on a single (111)[112] system, until the activation of intersecting slip systems brings about the onset of the secondary creep stage. The extent of primary creep has been shown to be reduced by application of a final ageing treatment at 870°C.</p> <p>Precipitate shear by paired dislocations in intense slip bands occurs during high strain-rate deformation at both ambient temperature and at 750°C. Application of a final ageing treatment at 870°C was found to increase the 0.2% proof stress and to bring about the activation of an alternative mode of precipitate shear by dissociated dislocations. The 870°C ageing treatment was shown to cause slight chemical changes at the γ/γ' interfaces, and these are believed to have caused the observed changes in mechanical properties.</p> |
| first_indexed | 2024-03-06T23:47:33Z |
| format | Thesis |
| id | oxford-uuid:71780c17-f658-40b6-9400-4ec40f5a7381 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:47:33Z |
| publishDate | 1984 |
| record_format | dspace |
| spelling | oxford-uuid:71780c17-f658-40b6-9400-4ec40f5a73812022-03-26T19:43:47ZStructure-property relations in superalloy single crystalsThesishttp://purl.org/coar/resource_type/c_db06uuid:71780c17-f658-40b6-9400-4ec40f5a7381TurbinesJet transportsBladesHeat resistant alloysEnglishPolonsky Theses Digitisation Project1984Hopgood, AMartin, JMartin, J<p>This research is concerned with a single crystal nickel-base superalloy which has been developed for application as a high pressure turbine blade material in jet aircraft engines. The microstructures and mechanical properties of superalloys, including the effects of heat-treatments, have been reviewed.</p> <p>The effects of heat-treatments on the γ' precipitate distributions have been investigated. During ageing at 900°C or 800°C, the precipitates adopt an irregular, rounded and highly interconnected microstructure, indicative of precipitate coalescence, whilst at higher ageing temperatures a regular cuboidal precipitate morphology is formed. The kinetics of precipitate coarsening have been investigated, and slight deviations from the power-law predicted by a number of theoretical models were observed. These deviations have been discussed in terms of a progressive transition in the dominant coarsening mechanism.</p> <p>Constant load creep tests were carried out, and although the tensile axis was nominally parallel to [001], the degree and direction of misorientation were found to be critical to the extent of the primary creep strain. Primary creep was shown to proceed by slip on a single (111)[112] system, until the activation of intersecting slip systems brings about the onset of the secondary creep stage. The extent of primary creep has been shown to be reduced by application of a final ageing treatment at 870°C.</p> <p>Precipitate shear by paired dislocations in intense slip bands occurs during high strain-rate deformation at both ambient temperature and at 750°C. Application of a final ageing treatment at 870°C was found to increase the 0.2% proof stress and to bring about the activation of an alternative mode of precipitate shear by dissociated dislocations. The 870°C ageing treatment was shown to cause slight chemical changes at the γ/γ' interfaces, and these are believed to have caused the observed changes in mechanical properties.</p> |
| spellingShingle | Turbines Jet transports Blades Heat resistant alloys Hopgood, A Structure-property relations in superalloy single crystals |
| title | Structure-property relations in superalloy single crystals |
| title_full | Structure-property relations in superalloy single crystals |
| title_fullStr | Structure-property relations in superalloy single crystals |
| title_full_unstemmed | Structure-property relations in superalloy single crystals |
| title_short | Structure-property relations in superalloy single crystals |
| title_sort | structure property relations in superalloy single crystals |
| topic | Turbines Jet transports Blades Heat resistant alloys |
| work_keys_str_mv | AT hopgooda structurepropertyrelationsinsuperalloysinglecrystals |