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You searched for subject:(Titanium Alloys Microtexture). Showing records 1 – 2 of 2 total matches.

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Indian Institute of Science

1. Nair, Shanoob Balachandran. Effect of Thermomechanical Processing on Microstructure And Microtexture Evolution in Titanium Alloys.

Degree: PhD, Faculty of Engineering, 2017, Indian Institute of Science

The properties of titanium alloys are based on alloy compositions and microstructures that consist of mixtures of the two allotropic modifications of titanium, the low temperature α (hcp) and the high temperature β (bcc) phases. This thesis deals with the hot working behaviour of three commercial titanium alloy compositions designated IMI834, Ti17 and Ti5553 with a focus and detailed analysis of the Ti5553 alloy. These alloys represent the differing uses of titanium alloys in the aerospace industry. IMI834 is a near α alloy used in high temperature creep resistant applications as compressor discs and blades in aeroengines. Ti17 is a high strength alloy α+β used at intermediate temperatures in fan and compressor discs of aeroengines, while Ti5553 is a high strength-high toughness metastable β alloy used in the undercarriages of aircraft. The three alloys have widely differing β transus temperatures (related to α phase stability) and compositions. Titanium alloys are vacuum arc melted and thermomechanically processed. This process involves ingot breakdown in β (bcc) phase, and subsequent thermomechanical processing in two-phase α+β (hcp+bcc) region at temperatures that typically involve volume fractions of α in lath or plate form ranging from 15% to about 30%. The thermomechanical processing breaks down lath α to spheroidal particles, a process known as globularisation. Chapter I of this thesis reviews the current understanding of the hot working of titanium alloys and microstructure evolution during the hot working process. Chapter II summarises the main experimental techniques used: the hot compression test, and subsequent microstructure and microtexture analysis by scanning electron microscopy and related electron back scattered diffraction techniques (EBSD), transmission electron microscopy and related precession electron diffraction techniques (PED) for orientation imaging. The starting structure in the α+β domain of hot work is generally not a random distribution of the 12 variant Burgers Orientation Relationship (BOR) between the α and β phases, (11̅0)β || (0001)α and <111>β || <112̅0>α . A variety of morphologies and distributions ranging from the typical colony structures of near α and α+β alloys to the fine distributions of variants arranged in a triangular fashion are observed with specific growth directions and habit planes. Chapter III describes a quantitative evaluation of α distribution that are typical of some of the starting structures for the hot working conditions used in this thesis, specifically in the Ti5553 alloy. For this purpose, a Matlab based script has been developed to measure the spatially correlated misorientation distribution. It was found that experimental spatially correlated misorientation distribution varies significantly from a random frequency for both pair and triplet wise distribution of α laths. The analysis of these structures by established techniques of analysis of self-accommodated structures based on strain energy minimisation shows that the observed variant… Advisors/Committee Members: Banerjee, Dipankar (advisor).

Subjects/Keywords: Titanium Alloys; Titanium Alloys Microstructure; Titanium Alloys Microtexture; Microstructure Evolution; Ti5553 Alloy; Materials Engineering

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APA (6th Edition):

Nair, S. B. (2017). Effect of Thermomechanical Processing on Microstructure And Microtexture Evolution in Titanium Alloys. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2678

Chicago Manual of Style (16th Edition):

Nair, Shanoob Balachandran. “Effect of Thermomechanical Processing on Microstructure And Microtexture Evolution in Titanium Alloys.” 2017. Doctoral Dissertation, Indian Institute of Science. Accessed January 16, 2021. http://etd.iisc.ac.in/handle/2005/2678.

MLA Handbook (7th Edition):

Nair, Shanoob Balachandran. “Effect of Thermomechanical Processing on Microstructure And Microtexture Evolution in Titanium Alloys.” 2017. Web. 16 Jan 2021.

Vancouver:

Nair SB. Effect of Thermomechanical Processing on Microstructure And Microtexture Evolution in Titanium Alloys. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2017. [cited 2021 Jan 16]. Available from: http://etd.iisc.ac.in/handle/2005/2678.

Council of Science Editors:

Nair SB. Effect of Thermomechanical Processing on Microstructure And Microtexture Evolution in Titanium Alloys. [Doctoral Dissertation]. Indian Institute of Science; 2017. Available from: http://etd.iisc.ac.in/handle/2005/2678


University of Michigan

2. Szczepanski, Christopher J. The Role of Microstructural Variability on the Very High Cycle Fatigue Lifetime Variability of an.

Degree: PhD, Materials Science and Engineering, 2008, University of Michigan

The fatigue behavior of structural components in the regime of very high cycle fatigue (VHCF) (106-109 cycles) has been attracting increased commercial interest as components are increasingly being called upon to perform in this regime of lifetimes. In VHCF, the applied stresses relative to the yield stress are very low. Therefore, it is presumed that a substantial portion of fatigue lifetime is consumed by the fatigue crack initiation process, and that cyclic plasticity only accumulates in microstructural neighborhoods that are susceptible to fatigue damage accumulation. Thus, microstructural heterogeneity is believed to significantly effect the fatigue lifetime variability. The very high cycle fatigue behavior of Ti-6246 has been investigated using ultrasonic fatigue techniques, and lifetimes ranging from 106-109 cycles have been observed. Fatigue cracks initiate by facet formation within αp grains. It has been found that the facets form in grains that are slightly larger than average and that the facets appear to form by a process of slip since the facet plane normals are oriented approximately 35-55° with respect to the tensile axis. Three characteristic fatigue crack initiation sites have been identified. These initiation sites, ranked in order of increasing fatigue resistance are: surface, subsurface with isolated facets, and subsurface with contiguous transgranular faceting. The texture of the material in these initiation regions is favorable for basal and prism slip. This texture is derived from the prior β texture, and a mechanism of fatigue crack initiation resulting from strain incompatibility has been proposed. Fatigue crack growth experiments have been completed to measure the influence of local texture on the ease of fatigue crack initiation and the resulting fatigue crack growth rates. These experiments have found that the controlling microstructural dimension is on the order of 20-25 µm. The texture appears to affect initiation of fatigue cracks from notches as well. For notches placed within neighborhoods favorably oriented for basal slip, fatigue crack initiation will be encouraged. However, for notches placed within microstructural regions unfavorably oriented for basal slip, fatigue crack initiation will be inhibited. Advisors/Committee Members: Jones, J. Wayne (committee member), Pollock, Tresa (committee member), Larsen, James M. (committee member), Pan, Jwo (committee member).

Subjects/Keywords: Ultrasonic Fatigue; Fatigue Crack Initiation; Alpha + Beta Titanium Alloys; Very High Cycle Fatigue; Microtexture; Materials Science and Engineering; Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Szczepanski, C. J. (2008). The Role of Microstructural Variability on the Very High Cycle Fatigue Lifetime Variability of an. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/61749

Chicago Manual of Style (16th Edition):

Szczepanski, Christopher J. “The Role of Microstructural Variability on the Very High Cycle Fatigue Lifetime Variability of an.” 2008. Doctoral Dissertation, University of Michigan. Accessed January 16, 2021. http://hdl.handle.net/2027.42/61749.

MLA Handbook (7th Edition):

Szczepanski, Christopher J. “The Role of Microstructural Variability on the Very High Cycle Fatigue Lifetime Variability of an.” 2008. Web. 16 Jan 2021.

Vancouver:

Szczepanski CJ. The Role of Microstructural Variability on the Very High Cycle Fatigue Lifetime Variability of an. [Internet] [Doctoral dissertation]. University of Michigan; 2008. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2027.42/61749.

Council of Science Editors:

Szczepanski CJ. The Role of Microstructural Variability on the Very High Cycle Fatigue Lifetime Variability of an. [Doctoral Dissertation]. University of Michigan; 2008. Available from: http://hdl.handle.net/2027.42/61749

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