| Mechanisms of Precipitation of Different Generations of Gamma-Prime Precipitates During Continuous Cooling of a Nickel Base Superalloy (PREPRINT) |
Aug 2012 |
33 pages |
| Authors:
J Tiley; G B Viswanathan; S Nag; R Banerjee; A R Singh; S Chattopadhyay; Y Ren; H L Fraser; UNIVERSITY OF NORTH TEXAS DENTON
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 | This paper focuses on developing a mechanistic understanding of the process of multiple nucleation bursts leading to the formation of multiple generations (or populations) with different size distributions, of gamma precipitates during the continuous cooling of a commercially used nickel base superalloy. This mechanistic understanding has been developed based on a number of critical experimental results; direct observation of the multiple nucleation bursts during in situ x-ray diffraction studies in ... |
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| Analysis of Deformation Substructures in a Notched LCF Sample Under Dwell Condition in a Ni-Based Superalloy (PREPRINT) |
Aug 2012 |
9 pages |
| Authors:
G B Viswanathan; Ken Bain; Dan Huber; S Jha; S Sam; J Tiley; Christopher Woodward; H L Fraser; UNIVERSITY OF NORTH TEXAS DENTON
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| Detailed transmission electron microscopy (TEM) studies were conducted on LCF Rene 104 alloy samples tested under dwell conditions to analyze the deformation substructures. Specifically, the focus was to investigate the effect of crack length, in other words, stress intensity factor range deltaK, on the deformation substructures. Thin foils were prepared by focused ion beam method (FIB) from two specific grains along the crack path at varying distances representing varying K ... |
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| On the Correlation between Morphology of alpha and Its Crystallographic Orientation Relationship with TiB and Beta in Boron Containing Ti-5Al-5Mo-5V-3Cr-0.5Fe Alloy (Preprint) |
Jan 2012 |
16 pages |
| Authors:
P Nandwana; S Nag; R Banerjee; D Hill; H L Fraser; J Tiley; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIR METALS CERAMICS AND NONDESTRUCTIVE EVALUATION DIV/METALS BRANCH
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| While the role of borides on the microstructure of titanium alloys has been discussed in many previous reports, this paper presents the first experimental evidence of (a) the three-dimensional geometry of alpha precipitates confirming their equiaxed morphology, as determined by reconstruction of serially-sectioned scanning electron microscopy images and, (b) the influence of crystallographic orientation relationship between Beta, TiB, and alpha phases on the morphology of alpha precipitates, investigated via detailed ... |
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| Use of Advanced Characterization Techniques to Study Structural and Compositional Transitions Across Solid State Interfaces (Preprint) |
Jul 2011 |
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| Authors:
J Tiley; G B Viswanathan; R Srinivasan; H L Fraser; R Banerjee; S Nag; J Y Hwang; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| The atomic-scale study of solid-solid interfaces in complex multi-phase multi-component systems is a challenging but important endeavor. This article highlights the coupling of recently developed advanced characterization techniques, such as high resolution scanning transmission electron microscopy (HRSTEM), carried out in an aberration-corrected microscope, and 3D atom probe (3DAP) tomography, to address the structural and compositional transition at the atomic scale across solid-solid interfaces, such as the gamma/gamma interface in Ni-base ... |
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| Precipitation of Ordered Phases in Metallic Solid Solutions: A Synergistic Clustering and Ordering Process (Preprint) |
Jul 2011 |
19 pages |
| Authors:
R Banerjee; A Singh; S Nag; G B Viswanathan; Jaimie Tiley; H L Fraser; UNIVERSITY OF NORTH TEXAS DENTON
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| The precipitation mechanism of ordered phases in metallic solid solutions has been a long-standing controversy due to the competing roles of chemical clustering (or phase separation) and chemical ordering. In the present study, this controversy has been resolved through the coupled use of aberration-corrected high-resolution scanning transmission electron microscopy and atom probe tomography. Thus, the experimental results, obtained at atomic resolution, can be interpreted satisfactorily only on the basis of ... |
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| A New Class of Solid-Solid Phase Transformations Involving a Composition-Dependent Displacive Component (Preprint) |
Jul 2011 |
6 pages |
| Authors:
S Nag; A Devaraj; N Gupta; S G Srinivasan; R Banerjee; R Srinivasan; R E Williams; H L Fraser; G B Viswanathan; J S Tiley; S Banerjee; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| Solid-solid displacive, structural phase transformations typically undergo a discrete structural change from the parent to the product phase. Coupling electron microscopy, three-dimensional atom probe, and first-principles computations, we present the first direct evidence of a novel mechanism for a coupled diffusional-displacive transformation in an important class of titanium-molybdenum alloys wherein the displacive component in the product phase changes continuously, as a function of its composition. These results cannot be explained ... |
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