Download or read book Dynamic Dislocation Mechanisms For the Anomalous Slip in a Single Crystal BCC Metal Oriented for Single Slip written by and published by . This book was released on 2007 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocation substructures of high-purity Mo single crystals deformed under uniaxial compression at room temperature to an axial strain of 0.6% were investigated in order to elucidate the underlying mechanisms for the {l_brace}0{bar 1}1{r_brace} anomalous slip in bcc metals [1], which is also known as the violation of Schmid law [2]. The test sample was oriented with the stress axis parallel to a nominal ''single-slip'' orientation of [{bar 2} 9 20], in which ({bar 1}01) [111] is the primary slip system that has a maximum Schmid factor (m = 0.5), which requires the lowest stress to operate among the twelve {l_brace}{bar 1}10{r_brace} 111 slip systems. Nevertheless, the recorded stress-strain curve reveals no easy-glide or single-slip stage; work hardening starts immediately after yielding. Moreover, the result of slip trace analysis indicates the occurrence of anomalous slip on both the (011) and (0{bar 1}1) planes, which according to the Schmid law requires relatively higher stresses to operate. TEM examinations of dislocation structures formed on the (101) primary slip plane reveal that in addition to the ({bar 1}01) [111] slip system, the coplanar ({bar 1}01) [1{bar 1}1] slip system which has a much smaller Schmid factor (m = 0.167) is also operative. Similarly, (0{bar 1}1) [111] (m = 0.25) is cooperative with the coplanar (0{bar 1}1) [{bar 1}11] slip system (m = 0.287) on the (0{bar 1}1) slip plane, and (011) [1{bar 1}1] (m = 0.222) is cooperative with the coplanar (011) [11{bar 1}] slip system (m = 0.32) on the (011) plane. The occurrence of {l_brace}0{bar 1}1{r_brace} anomalous slip is accordingly proposed to be originated from the cooperative dislocation motion of the ± 1/2 [111] and ± 1/2 [1{bar 1}1] dislocations on the ({bar 1}01) slip plane; the mutual interaction and blocking of ± 1/2 [111] and ± 1/2 [1{bar 1}1] dislocations not only cause an increase of glide resistance to the dislocation motion on the ({bar 1}01) plane but also render the ± 1/2 [111] and ± 1/2 [1{bar 1}1] screw dislocations to cross slip and propagate from the ({bar 1}01) slip plane onto the (0{bar 1}1) and (011) intersecting slip planes. That is, the ± 1/2 [111] screw dislocations cross slip from (111) onto (011), and the ± 1/2 [1{bar 1}1] screw dislocations cross slip from (111) onto (011), which subsequently render another two slip systems, (0{bar 1}1) [{bar 1}11] and (011) [11{bar 1}], to become operative. As a result, all 1/2111-type dislocations, i.e. all 111 slip, take part in the plastic deformation of the [{bar 2} 9 20]-oriented single-crystal Mo.
Download or read book On the Micromechanisms of Anomalous Slip in BCC Metals written by L. L. Hsiung and published by . This book was released on 2005 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocation substructures developed in high-purity Mo single crystals deformed under uniaxial compression at room temperature to a total strain of {approx} 0.5% with a strain rate of 1 s{sup -1} have been investigated using transmission electron microscopy (TEM) techniques in order to elucidate the underlying micromechanisms of the anomalous operation of {l_brace}0{bar 1}1{r_brace} slip systems, i.e. Schmid-law violation, in bcc metals. The crystals were oriented with the stress axis parallel to a nominal single-slip orientation of [{bar 2}920], in which the ({bar 1}01)[111] slip system is the only system having a maximum value of Schmid factor (m = 0.5). Nevertheless, the recorded stress-strain curve reveals no single-slip or easy-glide stage, and the anomalous slip occurs in both (011) and (0{bar 1}1) planes. TEM examination of the dislocation structure in the ({bar 1}01) primary slip plane reveals that in addition to the operation of the ({bar 1}01)[111] slip system, the coplanar ({bar 1}01)[1{bar 1}1] slip system that has a much smaller Schmid factor (m = 0.167) is also operative. Similarly, the (0{bar 1}1)[111] slip system (m = 0.25) is cooperative with the coplanar (0{bar 1}1)[{bar 1}11] system (m = 0.287), and the (011)[1{bar 1}1] slip system (m = 0.222) is cooperative with the coplanar (011)[11{bar 1}] system (m = 0.32). The occurrence of {l_brace}0{bar 1}1{r_brace} anomalous slip is accordingly proposed to be initiated from the cooperative dislocation multiplication and mutual trapping and blocking of 1/2[111] and 1/2[1{bar 1}1] coplanar dislocation arrays in the ({bar 1}01) plane. The resulted internal stresses render the propagation of both 1/2[111] and 1/2[1{bar 1}1] screw dislocations from the ({bar 1}01) plane onto the {l_brace}0{bar 1}1{r_brace} planes and subsequently result in the occurrence of anomalous slip.
Download or read book Dislocation Dynamics written by Alan R. Rosenfield and published by . This book was released on 1968 with total page 806 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocations in Solids written by and published by Elsevier. This book was released on 2009-08-28 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: New materials addressed for the first time include the chapters on minerals by Barber et al and the chapter on dislocations in colloidal crystals by Schall and Spaepen. Moriarty et al extend the first principles calculations of kink configurations in bcc metals to high pressures, including the use of flexible boundary conditions to model dilatational effects. Rabier et al clarify the issue of glide-shuffle slip systems in diamond cubic and related III-V compounds. Metadislocations, discussed by Feuerbacher and Heggen, represent a new type of defect in multicomponent metal compounds and alloys. - Kink mechanisms for dislocation motion at high pressure in bcc metals - Dislocation core structures identified in silicon at high stress - Metadislocations, a new type of defect, identified and described - Extension of dislocation concepts to complex minerals - First observations of dislocations in colloidal crystals
Download or read book Dislocations in Solids written by and published by Elsevier. This book was released on 2007-05-16 with total page 681 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocations are lines of irregularity in the structure of a solid analogous to the bumps in a badly laid carpet. Like these bumps they can be easily moved, and they provide the most important mechanism by which the solid can be deformed. They also have a strong influence on crystal growth and on the electronic properties of semiconductors.·Influence of dislocations on piezoelectric behavior·New mechanisms for hardening in twinned crystals·Bringing theories of martensite transformation into agreement·Atomic scale motion of dislocations in electron microscopy·Dislocation patterns deduced from X-ray diffraction·Role of dislocations in friction·Dislocation motion in quasicrystals
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1974 with total page 1296 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book On the Mechanism of Anomalous Slip in BCC Metals written by and published by . This book was released on 2011 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocation Dynamics Simulations of Persistent Slip Bands During Fatigue of FCC Metals written by Can Erel and published by . This book was released on 2015 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fatigue of an engineering structure originates from the nucleation of micro-size cracks. The accumulation of these micro-cracks ultimately results in the failure of the structure. In FCC materials, the localization of plastic strain into persistent slip bands (PSBs) during fatigue results in the initiation of micro-cracks at sites where the band emerges at the crystal surface. The main objective of this study is to explore the underlying dislocation mechanisms which significantly contribute to the fatigue deformation in FCC materials. In this context, a dislocation dynamics approach is employed in order to simulate the plasticity and fatigue evolution in FCC crystals. We focus on the role of dipolar loops, which are the main ingredients of dislocation dense regions in FCC crystals, in the patterning of dislocation structures. The simulation results show that the interaction between glide dislocations and dipolar loops may lead to the refinement of dipolar loops. It is also likely that such an interaction results in a sessile dislocation configuration. We also investigate the clustering of a group of dipolar loops under the influence of a glide dislocation moving back and forth under fatigue. We identify a new dipolar loop dragging mechanism dominant in spontaneous clustering of relatively large dipolar loops. Furthermore, we explore the dislocation dipole mechanisms leading to the occurrence of slip avalanches in FCC single crystals. We then present a persistent slip band model to investigate the evolution of dislocation structure and ultimately crack nucleation in fatigued FCC materials. The PSB model is cyclically deformed at two different plastic strain amplitudes corresponding to a partly formed PSB and a fully formed PSB. Comparing the stress strain responses of these two cases, it is shown that there is a correlation between the hardening behavior of a PSB and dislocation densities in channels of the PSB. The simulation results also reveal that, for the case of partly formed PSB, strain is substantially carried by the movement of screw dislocations, while, for the case of fully formed PSB, the edge dislocations moving in the direction of burgers vector plays a significant role in strain carrying.
Download or read book Dislocations in Metals written by American Institute of Mining and Metallurgical Engineers. Institute of Metals Division and published by . This book was released on 1954 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Classical Theory Of Crystal Dislocations From Iron To Gallium Nitride written by Hiroyasu Saka and published by World Scientific. This book was released on 2017-09-11 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book consists of two parts: Part 1 is a standard text of dislocation theory. Mathematics is avoided as much as possible. Part 2 describes application of dislocation theory, which includes mechanical properties (including the inverse temperature dependence of strength) and dislocations in functional materials such as Si, GaN and SiC and dislocations in a thin crystal such as an epitaxial layer. This is what has been long anticipated among researchers in industry.The book contains about 330 illustrations (mostly originals by the author) and the pictures obtained by the author by means of in-situ experiment in a transmission electron microscope over the past 50 years.This book includes many exercises, which the author found useful when he was teaching in Department of Materials Science and Engineering of Nagoya University to stimulate their interests in dislocation theory.
Download or read book Dislocation Generation and Motion in B2 NiAl Single Crystals written by Biman Ghosh and published by . This book was released on 2003 with total page 410 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 The Dislocation Structure and Slip Systems in beta NiAl Single Crystals Deformed in High Temperature Creep written by Joze Bevk and published by . This book was released on 1968 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Introduction to Dislocations written by Derek Hull and published by Butterworth-Heinemann. This book was released on 1995 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides an essential basis for an understanding of many of the physical and mechanical properties of crystalline solids. This new edition has been extensively revised and updated to reflect developments in the understanding of the subject, whilst retaining the clarity and comprehensibility of the original text. Substantial new sections are included, notably in topics relating to experiemental technqiues, the elastic properties of dislocations, forces on dislocations, dislocations in particular crystal structures, the dislocation content of boundaries, and the strength of crystalline solids.
Download or read book Fundamental Aspects of Dislocation Interactions written by G. Kostorz and published by Elsevier. This book was released on 2013-09-03 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III covers the papers presented at a European Research Conference on Plasticity of Materials-Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III, held on August 30-September 4, 1992 in Ascona, Switzerland. The book focuses on the processes, technologies, reactions, transformations, and approaches involved in dislocation interactions. The selection first offers information on work softening and Hall-Petch hardening in extruded mechanically alloyed alloys and dynamic origin of dislocation structures in deformed solids. Discussions focus on stress-strain behavior in relation to composition, structure, and annealing; comparison of stress-strain curves with work softening theory; sweeping and trapping mechanism; and model of dipolar wall structure formation. The text then ponders on plastic instabilities and their relation to fracture and dislocation and kink dynamics in f.c.c. metals studied by mechanical spectroscopy. The book takes a look at misfit dislocation generation mechanisms in heterostructures and evolution of dislocation structure on the interfaces associated with diffusionless phase transitions. Discussions focus on dislocation representation of a wall of elastic domains; equation of equilibrium of an elastic domain; transformation of dislocations; and theoretical and experimental background. The selection is a valuable reference for readers interested in dislocation interactions.
Download or read book Dislocations Mesoscale Simulations and Plastic Flow written by L. Kubin and published by Oxford University Press (UK). This book was released on 2013-04-18 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past twenty years, new experimental approaches, improved models and progress in simulation techniques brought new insights into long-standing issues concerning dislocation-based plasticity in crystalline materials. Dislocation dynamics simulations are becoming accessible to a wide range of users. This book presents to students and researchers in materials science and mechanical engineering a comprehensive coverage of the physical body of knowledge on whichthey are based. This includes classical studies, which are too often ignored, recent experimental and theoretical advances, as well as a discussion of selected applications on various topics.
Download or read book Introduction to Dislocations written by Derek Hull and published by . This book was released on 1965 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:
