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Title: Degradation of TiNi-based shape memory alloys (SMAs) during thermo-mechanical cycling
Author: Haenschke, Titus Paul
ISNI:       0000 0004 2741 4676
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2013
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This thesis is aimed at the identification of causes for the instability of Ti-49.8Ni and Ti-40.8Ni-9Cu (at.%)shape memory alloys during thermomechanical cycling. To assess the macroscopical and microstructural behaviour several techniques were employed. Thermo-mechanical tests (TMT) revealed that TiNi did not stabilise under the tested conditions. In contrast, TiNiCu showed a more stable behaviour. Whereas the maximum testing temperatures were found to be detrimental for the strain output in TiNi, none such influence could be found in TiNiCu. In TiNiCu increasing stresses seems to prevent the material stabilisation.During in-situ TMTs under high energy X-ray radiation in a synchrotron, microstructural factors influencing the stability of the material were assessed. No hint on a negative influence of remnant or intermediate phases and texture or variant selection was found. Instead increasingly negative strains build up in austenite possibly causing instabilities. In TiNiCu differences in the processing where found to cause changes in the phase transformation temperatures. These could be linked with differences in the chemical composition and in the level of inhomogeneity of precipitates.
Supervisor: Not available Sponsor: Rolls-Royce
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: T Technology (General) ; TL Motor vehicles. Aeronautics. Astronautics ; TN Mining engineering. Metallurgy