Download or read book Shock induced Alpha omega Structural Phase Transformation of Titanium written by B. Sadigh and published by . This book was released on 2004 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Titanium alpha omega Phase Transformation Pathway and a Predicted Metastable Structure written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A titanium is a highly utilized metal for structural lightweighting and its phases, transformation pathways (transition states), and structures have scientific and industrial importance. Using a proper solid-state nudged elastic band method employing two climbing images combined with density functional theory DFT + U methods for accurate energetics, we detail the pressure-induced [alpha] (ductile) to [omega] (brittle) transformation at the coexistence pressure. We also find two transition states along the minimal-enthalpy path and discover a metastable body-centered orthorhombic structure, with stable phonons, a lower density than the end-point phases, and decreasing stability with increasing pressure.

Download or read book Omega Phase Formation in Titanium and Titanium Alloys written by and published by . This book was released on 1992 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the response of titanium alloys to dynamic loading is receiving increased attention in the literature (particularly in the area of shear-band formation), a more limited experimental database exists concerning the detailed structure/property relationships of titanium alloys subjected to shock loading. In this study, preliminary results concerning the influence of alloy chemistry on the property of omega-phase formation and its structure in three titanium alloys are presented. The influence of shock-wave deformation on the phase stability and substructure evolution of high-purity (low-interstitial) titanium, A-70 (3700 ppm oxygen) titanium, and Ti-6Al-4V were probed utilizing real-time velocity interferometry (VISAR) and soft'' shock-recovery techniques. VISAR wave profiles of shock-loaded high-purity titanium revealed the omega-phase pressure-induced transition to occur at approximately 10.4 GPa. Wave profile measurements on A-70 Ti shocked to pressures up to 35 GPa and Ti-6Al-4V shocked to pressures up to 25 GPa exhibited no evidence of a three-wave structure indicative of a pressure-induced phase transition. Neutron and X-ray diffractometry and TEM analysis confirmed the presence of retained [omega]-phase in the electrolytic-Ti and the absence of [omega]-phase in the shock-recovered A-70 Ti and Ti-6Al-4V. Suppression of the [alpha]-[omega] phase transition in A-70 Ti, containing a high interstitial oxygen content, is seen to simultaneously correlate with suppression of deformation twinning. Neutron diffraction was used to measure the in-situ bulk lattice constants and volume fraction of the [alpha] and [omega] phases in the recovered high-purity titanium samples that were shock loaded. The influence of alloy content on the kinetics of formation/retention of [omega]-phase and substructure evolution is discussed and contrasted in light of previous literature studies.

Download or read book Titanium Alloys written by A.K.M. Nurul Amin and published by BoD – Books on Demand. This book was released on 2012-03-16 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first section of the book includes the following topics: fusion-based additive manufacturing (AM) processes of titanium alloys and their numerical modelling, mechanism of ?-case formation mechanism during investment casting of titanium, genesis of gas-containing defects in cast titanium products. Second section includes topics on behavior of the (? + ?) titanium alloys under extreme pressure and temperature conditions, hot and super plasticity of titanium (? + ?) alloys and some machinability aspects of titanium alloys in drilling. Finally, the third section includes topics on different surface treatment methods including nanotube-anodic layer formation on two phase titanium alloys in phosphoric acid for biomedical applications, chemico-thermal treatment of titanium alloys applying nitriding process for improving corrosion resistance of titanium alloys.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Theoretical Study of the HCP to Omega Martensitic Phase Transition in Titanium written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Under pressure, titanium transforms from the hexagonal-closed-packed (hcp) structure to the high pressure omega phase. This phase transition from hcp (alpha) to omega (omega) is martensitic: there is a macroscopic cell change, described by a strain tensor, coupled with microscopic internal relaxations of the unit cell, described by shuffle vectors. In addition, the transformation occurs directly and without diffusion. Despite this, the atomistic transformation was not known. Trace amounts (1 at.%) of oxygen impurities shut down the shock-induced transformation. Ab initio, tight-binding, and classical potential calculations model the hcp to omega transformation, and the effects of impurities on the transformation. A new pathway generation and sorting algorithm systematically searches through all possible pathways to find the most probable homogeneous mechanism. A new mechanism is found with a barrier 4 times lower than any other homogeneous mechanisms, even when nucleation effects are considered. Using molecular dynamics, the transformation from hcp to omega moves across the interphase boundary under pressure at a finite temperature. The interstitial impurities oxygen, nitrogen, carbon, and substitutional impurities aluminum and vanadium shift both the energy barrier between and the relative energies of alpha and omega; these changes explain the shutdown of the alpha to omega transformation by oxygen and aluminum. The final result is an atomistic understanding of the Ti alpha to omega transformation: moving from the homogeneous energy barrier to nucleation effects to finite temperature to the effect of impurities. This serves as a template for future studies of the atomistic mechanisms of other martensitic transformations.

Download or read book Alpha Omega Transition in Titanium written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the construction of free energy functions for the [alpha] and [omega] phases of Ti. These free energies combine information from ambient pressure, static high pressure, and shock wave measurements as well as first principles total energy calculations. The Hugoniot data are analyzed in terms of this equation of state. The Hugoniot consists of three segments: a metastable [alpha]-phase region, a transition region, and an [omega]-phase branch. The extent of the metastability and time resolved wave profiles are discussed in terms of a model in which the transformation rate depends exponentially on the pressure, an assumption which is motivated by static high-pressure data. This picture is consistent with the observed wave shapes and with the observation that the apparent transformation pressure is dependent on the peak shock pressure.

Download or read book Reviews in Computational Chemistry written by Abby L. Parrill and published by John Wiley & Sons. This book was released on 2017-03-07 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Reviews in Computational Chemistry series brings together leading authorities in the field to teach the newcomer and update the expert on topics centered on molecular modeling. • Provides background and theory, strategies for using the methods correctly, pitfalls to avoid, applications, and references • Contains updated and comprehensive compendiums of molecular modeling software that list hundreds of programs, services, suppliers and other information that every chemist will find useful • Includes detailed indices on each volume help the reader to quickly discover particular topics • Uses a tutorial manner and non-mathematical style, allowing students and researchers to access computational methods outside their immediate area of expertise

Download or read book Influence of the Shock Induced Alpha epsilon Transition in Fe and the Alpha omega Transitions in Ti and Zr on Post shock Substructure Evolution and Mechanical Behavior written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metals Abstracts written by and published by . This book was released on 1998 with total page 1042 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shock induced Defects in Bulk Materials written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper examples of the shock-induced defects produced during shock compression which correlate with microstructure/mechanical property changes induced in materials due to shock prestraining are discussed. The characteristics of the shock impulse(peak shock pressure, pulse duration, and rarefaction rate) imparted to the material under investigation and the shock-induced defects produced in numerous metals and alloys are compared with their deformation behavior at ordinary rates of deformation. Examples of the range of defects observed in shock-recovered metals and alloys, include: dislocations, deformation twins, point defects, and residual metastable remnants from pressure-induced phase transformations. Results concerning the influence of interstitial content on the propensity of [omega]-phase formation and its structure in high-purity and A-7O Ti are presented. The influence of shock-wave deformation on the phase stability and substructure evolution of high-purity (low-interstitial) titanium and A-7O (3,700 ppm oxygen) titanium were probed utilizing real-time velocity interferometry (VISAR) and soft shock-recovery techniques. Suppression of the [alpha]-[omega] pressure-induced phase transformation in A-70 Ti, containing a high interstitial oxygen content, is seen to simultaneously correspond with the suppression of deformation twinning.

Download or read book The Science Technology and Application of Titanium written by R. I. Jaffee and published by Elsevier. This book was released on 2013-09-24 with total page 1225 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Science, Technology and Application of Titanium contains the proceedings of an International Conference organized by the Institute of Metals, The Metallurgical Society of AIME, and the American Society for Metals in association with the Japan Institute of Metals and the Academy of Sciences of the USSR and held at the Royal Festival Hall in London, on May 21-24, 1968. The papers explore scientific and technological developments as well as applications of titanium and cover topics ranging from processing of titanium to its chemical and environmental behavior, physics, thermodynamics, and kinetics. Deformation and fracture, phase transformations and heat treatment, and alloying are also discussed. This book is comprised of 114 chapters and begins with an overview of the titanium industry in Europe and the United States. The reader is then introduced to primary and secondary fabrication of titanium; corrosion and oxidation; physical properties of titanium alloys; interaction of titanium with elements of the periodic system; and elastic interactions between dislocations and twin and grain boundaries in titanium. The crystallography of deformation twinning in titanium is also examined, along with superplasticity and transformation plasticity in titanium. The remaining chapters focus on interstitial strengthening of titanium alloys; mechanism of martensitic transformation in titanium and its alloys; phase relationships in titanium-oxygen alloys; strengthening of titanium alloys by shock deformation; and titanium hot forming. This monograph will be of interest to chemists and metallurgists.

Download or read book Phase and Structural Changes in Titanium Under Pulse Loadings written by I. O. Pashkov and published by . This book was released on 1973 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The presence of phase transition under an applied dynamic pressure similar to the (alpha to omega) phase transition realized with a static load was established. A methodology was worked out for fixing the high-temperature phase in pure titanium using pre-freezing in liquid nitrogen and an applied dynamic pressure produced by intense shock waves. A probable mechanism for observing the formation and fixing of the (beta)-phase in titanium was proposed. The described methodology for fixation can be used when studying the high-temperature phases of other pure metals.

Download or read book Phase Stability and Phase Transformations written by R. Krishnan and published by . This book was released on 1985 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the International Conference on Phase Stability and Phase Transformations, Bombay, India, 1984

Download or read book Energy Research Abstracts written by and published by . This book was released on 1992 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metals Abstracts Index written by and published by . This book was released on 1984 with total page 1034 pages. Available in PDF, EPUB and Kindle. Book excerpt: