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Title: Optimising fatigue through the control of texture in titanium alloys
Author: Suddell, B. C.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2001
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Titanium alloys are used extensively throughout the aerospace sector in blades and discs of the low and intermediate sections of the compressors of modern Aeroengines. Titanium is used primarily as it has a high strength-to-weight ratio and good Fatigue and Creep resistance. Titanium 6-4 (Ti-6Al-4V) is the general "Workhorse" alloy of the Titanium family of alloys and has been extensively studied over the past 50 yeas. It is known that texture plays an important role in terms of its effect on the materials mechanical properties. The mechanical response of textured Ti 6/4 plate material is assessed through an evaluation of monotonic properties under tension and torsion loading and fatigue testing of plain and notched specimen geometries. Significant variations in modulus, yield strength, ultimate tensile strength and ductility are demonstrated for test pieces taken from the plate materials parallel to either the transverse or longitudinal rolling direction or perpendicular to the longitudinal direction i.e. in the Short Transverse orientation. Cyclic performance is also shown to be sensitive to orientation with different cyclic stress-strain curves applying to each orientation. The relationship between the principle stress axis and the dominant basal plane texture is shown to control fatigue crack initiation lives and the ultimate mode of fracture. These effects are discussed with reference to the inherent, anisotropic mechanical response of α+β titanium alloys, which results from the hexagonal crystallographic form of the α phase and the availability of preferential slip systems. The anisotropic response could be utilised to an engineering advantage by matching critical stressing directions to the specific properties offered by the texture.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available