Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537887
Title: Characterisation of gas-atomised powders of [gamma]-titanium aluminides
Author: Gouma, Pelagia-Irene
Awarding Body: The University of Birmingham
Current Institution: University of Birmingham
Date of Award: 1996
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Abstract:
Gas-atomised powders of the Ti-48A1-2Nb-2Mn system have been produced from ingot material using the IRC facility and these powders have been examined before and after a range of HIPping treatments. The as-atomised powders and consolidated samples have been examined using optical microscopy, analytical scanning, transmission electron microscopy, and XPS spectroscopy. Some property measurements have been carried out on HIPped samples. The structure of the powders was, as expected, a function of particle diameter, with small particles (below 40μm diameter) showing the largest fraction of retained alpha. Detailed examination of the HIPped samples revealed a range of heterogeneous structures which were present in all size fractions. In particular, regions were found which are about 100μm in diameter where the Al content is very low, typically about 5% lower than the average alloy content, and which act as fracture-initiation sites during tensile testing. Examination of HIPped powders produced at different atomisation plants show similar regions with very low aluminium contents. The origin of these regions is argued to be the mushy zone which is present in the cold wall furnaces used to melt the alloy prior to atomisation. It is shown that heat-treatments aimed at removing these heterogeneities can be carried out as part of the HIPping process. The significance of these observations for powder-route products is briefly discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.537887  DOI: Not available
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