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Title: Development of improved α + β titanium aerospace alloys
Author: Basterretxea-Gomez, A.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2005
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The design of titanium alloys has been traditionally conditioned by the development of relatively “randomly textured” materials rendering isotropic mechanical properties. The present project aims to gain a deeper insight into this area. In particular, the influence that processing variables such as (1) the Rolling Temperature, (2) The Rolling Direction, (3) The Reduction Percentage and (4) Heat Treatments have on the microstructure/texture development and related mechanical properties is given special attention. Mechanical properties analysed in the present project include fatigue crack threshold and crack propagation testing, strain control low cycle fatigue testing, load control low cycle fatigue testing and load control high cycle fatigue testing. An increase of rolling percentage favours recrystallisation of the alpha phase and aligning of textures towards the transverse direction (TD). Heat treated plates show similar texture orientations to those obtained for the un-heat-treated material, with a slight decrease in texture intensities.  Material rolled uni-directionally above the beta transus shows strong basal-like texture. As the material is further rolled, now below the beta transus, textures start to become aligned towards the TD. Texture intensities drop substantially in the process. Samples tested at 90 degrees with respect to the rolling direction (RD) show higher threshold values than those tested at 0 degrees. The overall best crack initiation performance is associated to microstructures characterised by elongated alpha grains embedded in an intergranular beta phase. Equiaxed microstructures show poorer crack initiation performance. Samples tested in Strain Control at 90 degrees show higher stabilised stress ranges and lower fatigue performance than those tested at 0 degrees. The highest Load Control figure lives are obtained for samples tested at 0 degrees.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available