Download or read book Influence of Beta Instabilities on the Early Stages of Nucleation and Growth of Alpha in Beta Titanium Alloys written by Soumya Nag and published by . This book was released on 2008 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Microstructural evolution in Beta Titanium alloys is an important factor that governs the properties exhibited by them. Intricate understanding of complex phase transformations in these alloys is vital to tailor their microstructures and in turn their properties to our advantage. One such important subject of study is the nucleation and growth of alpha precipitates triggered by the compositional instabilities in the beta matrix, instilled in them during non equilibrium heat treatments. The present work is an effort to investigate such a phenomenon. Here studies have been conducted primarily on two different Beta-Titanium alloys of commercial relevance- Ti5553 (Ti-5Al-5Mo-5V-3Cr-0.5Fe), an alloy used in the aerospace industry for landing gear applications and, TNZT (Ti-35Nb-7Zr-5Ta), a potential load bearing orthopedic implant alloy. Apart from the effect of thermal treatment on these alloys, the focus of this work is to study the interplay between different alpha and beta stabilizers present in them. For this, advanced nano-scale characterization tools such as High Resolution STEM, High Resolution TEM, EFTEM and 3D Atom Probe have been used to determine the structure, distribution and composition of the non equilibrium instabilities such as beta phase separation and omega phase, and also to investigate the subsequent nucleation of stable alpha. Thus in this work, very early stages of phase separation via spinodal decomposition and second phase nucleation in titanium alloys are successfully probed at an atomic resolution. For the first time, atomically resolved HRSTEM Z-contrast image is recorded showing modulated structures within the as-quenched beta matrix. Also in the same condition HRTEM results showed the presence of nanoscale alpha regions. These studies are revalidated by conventional selected area diffraction and 3D atom probe reconstruction results. Also TEM dark field and selected area diffraction studies are conducted to understand the effect of quenching and subsequent aging of omega precipitates. Using 3D atom probe tomography, the elemental partitioning involved in coarsening of omega is investigated in detail. Finally by performing a series of well planned heat treatments, an effort is made to reason out the influence of these instabilities on the morphology, volume fraction and nucleation site of alpha.

Download or read book TMS 2018 147th Annual Meeting Exhibition Supplemental Proceedings written by The Minerals, Metals & Materials Society and published by Springer. This book was released on 2018-02-03 with total page 898 pages. Available in PDF, EPUB and Kindle. Book excerpt: This collection features papers presented at the 147th Annual Meeting & Exhibition of The Minerals, Metals & Materials Society.

Download or read book Titanium Alloys written by Maciej Motyka and published by BoD – Books on Demand. This book was released on 2019-11-27 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Titanium alloys, due to unique physical and chemical properties (mainly high relative strength combined with very good corrosion resistance), are considered as an important structural metallic material used in hi-tech industries (e.g. aerospace, space technology). This book provides information on new manufacturing and processing methods of single- and two-phase titanium alloys. The eight chapters of this book are distributed over four sections. The first section (Introduction) indicates the main factors determining application areas of titanium and its alloys. The second section (Manufacturing, two chapters) concerns modern production methods for titanium and its alloys. The third section (Thermomechanical and surface treatment, three chapters) covers problems of thermomechanical processing and surface treatment used for single- and two-phase titanium alloys. The fourth section (Machining, two chapters) describes the recent results of high speed machining of Ti-6Al-4V alloy and the possibility of application of sustainable machining for titanium alloys.

Download or read book The Effects of Alloying Elements in Titanium written by D. J. Maykuth and published by . This book was released on 1961 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Mechanisms for Fine Scale Alpha Phase in Beta Titanium Alloys written by Amit Kishan Behera and published by LAP Lambert Academic Publishing. This book was released on 2014-09-18 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work focuses on a study of different mechanisms to engineer homogeneously distributed fine sized alpha precipitates in the beta matrix of beta titanium alloys. The precipitation of metastable phases (such as omega phase) upon low temperature aging and their influence on alpha precipitation is studied in detail. The precipitation sequence on direct aging above the omega solvus temperature is also assessed. The structural and compositional evolution of precipitate phase is determined using multiple characterization tools (3DAP, TEM, SEM, Synchrotron XRD). The possibility of occurrence of other non-classical precipitation mechanisms that do not require heterogeneous nucleation sites are also analyzed. Lastly, the influence of interstitial element, oxygen on alpha precipitation during the oxidation of Beta 21S has been determined. The ingress of oxygen and its influence on microstructure have also been correlated to measured mechanical properties.

Download or read book The Effect of Addition Elements on the Rate of Beta Grain Growth in Alpha beta and Beta Titanium Alloys written by F. A. Crossley and published by . This book was released on 1962 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: TILITY THROUGH A SCAVENGING ACTION. (Author).

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 1006 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceedings of the 13th World Conference on Titanium written by Vasisht Venkatesh and published by John Wiley & Sons. This book was released on 2016-04-26 with total page 4024 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the Proceedings of the 13th World Conference on Titanium.

Download or read book Microstructural Stability and Thermomechanical Processing of Boron Modified Beta Titanium Alloys written by Balakrishna Cherukuri and published by . This book was released on 2008 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main objectives during primary processing of titanium alloys is to reduce the prior beta grain size. Producing an ingot with smaller prior beta grain size could potentially eliminate some primary processing steps and thus reduce processing cost. Trace additions of boron have been shown to decrease the as-cast grain size in alpha + beta titanium alloys. The primary focus of this dissertation is to investigate the effect of boron on microstructural stability and thermomechanical processing in beta titanium alloys. Two metastable beta titanium alloys: Ti-15Mo-2.6Nb-3Al-0.2Si (Beta21S) and Ti-5Al-5V-5Mo-3Cr (Ti5553) with 0.1 wt% B and without boron additions were used in this investigation. Significant grain refinement of the as-cast microstructure and precipitation of TiB whiskers along the grain boundaries was observed with boron additions. Beta21S and Beta21S-0.1B alloys were annealed above the beta transus temperature for different times to investigate the effect of boron on grain size stability. The TiB precipitates were very effective in restricting the beta grain boundary mobility by Zener pinning. A model has been developed to predict the maximum grain size as a function of TiB size, orientation, and volume fraction. Good agreement was obtained between model predictions and experimental results. Beta21S alloys were solution treated and aged for different times at several temperatures below the beta transus to study the kinetics of alpha precipitation. Though the TiB phase did not provide any additional nucleation sites for alpha precipitation, the grain refinement obtained by boron additions resulted in accelerated aging. An investigation of the thermomechanical processing behavior showed different deformation mechanisms above the beta transus temperature. The non-boron containing alloys showed a non-uniform and fine recrystallized necklace structure at grain boundaries whereas uniform intragranular recrystallization was observed in boron containing alloys. Micro-voids were observed at the ends of the TiB needles at high temperature, slow strain rates as a result of decohesion at the TiB / matrix interfaces. At low temperatures and faster strain rates micro voids were also formed due to fracture of TiB needles. Finite element analysis on void formation in TiB containing alloys were in agreement with experimental observations. Microhardness and tensile testing of as-cast + forged and aged Beta21S and Ti5553 alloys with and without boron did not show any significant differences in mechanical properties. The primary benefits of boron modified alloys are in as-cast condition.

Download or read book Titanium Alloys written by Jan Sieniawski and published by BoD – Books on Demand. This book was released on 2013-05-15 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book contains six chapters and covers topics dealing with biomedical applications of titanium alloys, surface treatment, relationships between microstructure and mechanical and technological properties, and the effect of radiation on the structure of the titanium alloys.

Download or read book Fundamental Studies of Beta Phase Decomposition Modes in Titanium Alloys written by H. I. Aaronson and published by . This book was released on 1985 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: These studies on diffusional phase transformations in titanium and related alloy systems are intended to develop further the scientific base needed to design alloys based upon these transformations which may exhibit significantly improved combinations of mechanical properties. Kinetics of beta yields alpha sub m massive transformation were compared with those of grain boundary proeutectoid alpha precipitation in Ti-Ag and Ti-Co alloys, using measured or calculated nucleation and growth kinetics data and Cahn analysis of overall transformation kinetics of grain boundary nucleated reactions, successfully explained presence of massive transformation only in Ti-Ag and alpha allotriomorphs only in Ti-Co. New explanation developed, on thermodynamic grounds, for replacement of 'normal' proeutectoid alpha plates with a well-formed 'black plates' alpha + lower reaction temperatures. Bainite nodules in hypereutectoid Ti-Cr and in hypoeutectoid Ti-Co and Ti-Fe were found to exhibit misfit dislocation and ledge structures. Nodules in Ti-Cr grew at approximately volume diffusion-controlled rates; but reanalysis is now needed in terms of ledge mechanism. Eutectoid alpha is often found to differ slightly in orientation from adjacent proeutectoid aplha plates.

Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 1118 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Development of Textures and Microstructures in Alpha beta Titanium Alloys written by Dhriti Bhattacharyya and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The relationship between the texture and the microstructure of both beta processed and alpha/beta processed Ti alloys has been examined in this study. In the beta-processed microstructures, it has been shown that two sets of alpha colonies sharing a common 0001 plane and rotated by 10.5° from each other may have growth directions which have very large angles of about 80.7° between them. Moreover, it was observed that alpha laths growing from certain prior beta grain boundaries sometimes shared common basal planes. In some special cases, the alpha laths growing into two different prior beta grains from the grain boundary between them had almost exactly the same orientation, although they had vastly different growth directions. Additionally, there were some cases in which alpha laths growing into different prior beta grains not only had the same crystallographic orientation, but also had the same growth direction. Scanning Electron Microscopy (SEM), Orientation Imaging Microscopy (OIM) and Transmission Electron Microscopy (TEM) have been used to investigate these phenomena and the existing theories of growth directions have been used in conjunction with the results obtained to explain them. In alpha/beta-processed alloys, the phenomenon of globularization of alpha laths breaks down the beta-processed microstructure and modifies the texture of these alloys. Samples of Ti-6Al-4V having colony and basketweave microstructures were hot deformed in the high alpha/beta temperature range and their microstructure and microtexture were examined by the use of SEM and OIM. It is shown that the samples which had a colony microstructure had greater "clustering" of grains with similar orientations than those having a basketweave microstructure. The mode of transformation on heating from the alpha to the beta phase was investigated by measuring the texture of both phases at different temperatures, in situ, using the HIPPO instrument at the Los Alamos Neutron Science Center. A comparison of the pole figures for both phases has allowed an insight into the mode of transformation of the alpha to the beta phase, and it appears that the beta phase forms by the growth of the preexisting beta, and not by fresh nucleation of beta in the alpha phase.

Download or read book Fundamental Studies of Beta Phase Decomposition Modes in Titanium and Related Alloy Systems written by and published by . This book was released on 1992 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: Throughout this final grant from AFOSR, the P.I. spent much of his time in the preparation of generic overviews of numerous major topics in diffusional phase transformations. These overviews dealt with homogeneous nucleation, interphase boundary structures in Ti-base alloys, effects of interphase boundary structure upon growth kinetics, shear vs. diffusional transformation mechanism (with emphasis upon linking macroscopic observations with processes proceeding at the atomic level), the mechanism (and definitions) of the bainite reaction and the influence of alloying elements upon the growth kinetics of grain boundary allotriomorphs of proeutectoid ferrite. A major overview of the ledge mechanism in vapor-crystal, liquid-crystal and crystal-crystal diffusional phase transformations, and a still broader overview of atomic mechanisms of diffusional nucleation and growth are nearing completion. Collaborative research with Dr. M.G. Hall of the University of Birmingham, U.K., on topics concerned with distinction between diffusional and shear mechanisms of transformation from the standpoints of crystallography and surface relief effects, has also made progress.

Download or read book Titanium and Titanium Alloys written by Christoph Leyens and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook is an excellent reference for materials scientists and engineers needing to gain more knowledge about these engineering materials. Following introductory chapters on the fundamental materials properties of titanium, readers will find comprehensive descriptions of the development, processing and properties of modern titanium alloys. There then follows detailed discussion of the applications of titanium and its alloys in aerospace, medicine, energy and automotive technology.

Download or read book Grain boundary Parameters Controlled Allotriomorphic Phase Transformations in Beta processed Titanium Alloys written by Vikas Dixit and published by . This book was released on 2013 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Allotriomorphic or grain-boundary alpha (GBA) is an unavoidable and important microstructural feature of the diffusional phase transformations in beta-processed titanium alloys. This phase has a negative influence on various mechanical properties, such as high cycle fatigue, fracture toughness, ductility etc. and has a profound influence on the overall microstructural evolution. In the present work, the evolution of GBA has been in explored relative to the grain-boundary parameters namely, misorientation angle and axis, and the GB plane. While the misorientation angle and axis relate to the crystallography of adjacent crystals and can easily be determined using diffraction based techniques, an accurate determination of the local crystallographic orientation of the GB plane is difficult because of its three-dimensional nature. To address this issue, two independent experimental approaches have been developed and validated by utilizing a combination of dual beam focused ion beam (FIB), SEM and electron back-scattered diffraction (EBSD) methods. Both these approaches considerably simplify the problem because of a relatively easier experimental set-up and a versatile methodology. The crystallographic variant selection and morphology of GBA have been subsequently evaluated relative to the quantified GB parameters. Results indicate that in alpha/beta- and beta-titanium alloys, the crystallographic variant selection and GB parameters control the evolution of the allotriomorphic alpha phase. In particular, misorientation angle/ axis parameters control the early precipitation of GBA. The grain-boundaries of those adjacent beta-grains that produce nearly parallel 111 and/or 101 poles are the preferred sites for the early nucleation of GBA. In addition, these closely related poles significantly influence the crystallographic variant selection criterion in a majority of cases and contribute to a considerable short-listing of the allowed variants of GBA. The morphology of GBA is primarily controlled by the inclination of the GB plane relative to the selected crystallographic variant of the Burgers-OR at grain-boundaries. In beta-titanium alloys, continuous GBA precipitates are produced when the GB plane orients nearly perpendicular to the invariant line of the contributing Burgers-OR. In case of alpha/beta-titanium alloys, the thickening of GBA is higher when the GB plane orients close to the broad-face or the habit plane of the Burgers-OR. It has been proposed for the first time that the crystallographic and morphological aspects of GBA and adjacent Widmanstätten alpha are interrelated and primarily dictated by the GB parameters. Specifically, once a particular crystallographic variant of GBA is chosen by a set of criterion, the crystallographic and morphological nature of adjacent Widmanstätten alpha is also predicted. The resulting Widmanstätten alpha morphology in combination with the nature of the GB parameters would control the growth (continuous or discrete) of GBA. Finally, transmission electron microscopy studies have revealed a variation in the interfacial structure between GBA and the adjacent beta grain, different from previously known well-defined interfacial structure between Widmanstätten alpha and the parent beta phase. The faceting of the interface as well as presence of new sets of misfit dislocations have been observed in this work.

Download or read book Effect of the Forming Conditions on the Microstructure of Two phase Alpha and Beta Titanium Alloys written by Mihalic, V and published by . This book was released on 1990 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: