Download or read book Dislocation Substructures in Cyclically Deformed Molybdenum Single Crystals written by Jose Antonio Planell-Estany and published by . This book was released on 1983 with total page 752 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocation Substructure Formed During Creep in Molybdenum Single Crystals written by Allan H. Clauer and published by . This book was released on 1968 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocation Substructure Induced by Creep in Molybdenum Single Crystals written by A. H. CLAUER and published by . This book was released on 1970 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocation Multiplication in the Early Stage of Deformation in Mo Single Crystals written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Initial dislocation structure in annealed high-purity Mo single crystals and deformation substructure in a crystal subjected to 1% compression have been examined and studied using transmission electron microscopy (TEM) techniques in order to investigate dislocation multiplication mechanisms in the early stage of plastic deformation. The initial dislocation density is in a range of 106 (almost equal to) 107 cm−2, and the dislocation structure is found to contain many grown-in superjogs along dislocation lines. The dislocation density increases to a range of 108 (almost equal to) 109 cm−2, and the average jog height is also found to increase after compressing for a total strain of 1%. It is proposed that the preexisting jogged screw dislocations can act as (multiple) dislocation multiplication sources when deformed under quasi-static conditions. The jog height can increase by stress-induced jog coalescence, which takes place via the lateral migration (drift) of superjogs driven by unbalanced line-tension partials acting on link segments of unequal lengths. The coalescence of superjogs results in an increase of both link length and jog height. Applied shear stress begins to push each link segment to precede dislocation multiplication when link length and jog height are greater than critical lengths. This ''dynamic'' dislocation multiplication source is suggested to be crucial for the dislocation multiplication in the early stage of plastic deformation in Mo.
Download or read book Rolled Molybdenum Single Crystals written by and published by . This book was released on 1964 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocations and Mechanical Properties of Single Crystal Molybdenum Silicide written by Stuart Andrew Maloy and published by . This book was released on 1994 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocations and mechanical properties of single crystal MoSi2 have been investigated. Specimens were tested in compression along (001), (021), and (771) axes at strain rates of 1 × 10̄−4/s and 1 × 10−5/s and at temperatures ranging from 900-1600°C in vacuum or argon. The yield stress along (001) was an order of magnitude greater than that measured along (021) or (771) and along all orientations the yield stress was strongly dependent on temperature. Rate jump tests performed along (001) at 1400°C revealed that the yield stress was rate sensitive with a stress exponent of 4. The activated slip systems were determined using optical slip trace analyses and techniques in transmission electron microscopy. Slip occurred via five different slip systems (11100, 13100, 1001/2111, 131/2331, and 111/2111) depending on the orientation, temperature and strain rate at which each test was performed. The critical resolved shear stress was determined for the activated slip systems from the measured 0.2% yield stresses. At 900-1100°C, the lo west critical resolved shear stresses were for slip on the 11100, 1101/2111 and 131/2331 slip systems while at 1200-1600°C the lowest critical resolved shear stresses were for slip on the 11100 and the 13100 slip systems. Decompositions and dissociations of 1/2331 and 1/2111 dislocations were observed. The 1/2331 dislocation decomposes into 1/2111 and 110 dislocations during deformation at temperatures above 900°C. This decomposition prevents deformation by the 1/2331 dislocation at temperatures of 1200°C and above. HREM observations of the core of a 1/2331 dislocation revealed that it was dissociated out of the 13 glide plane after deformation at 900°C, while observations of the core of a 1/2111 dislocation after deformation at 1100°C revealed that it was dissociated by glide in the 110 plane. These core structures strongly affect the Peierls stress for glide of the 1/2331 and 1/2111 dislocations. Large climb dissociations of the 1/2111 and 1/2331 dislocations were also observed on the (001) plane, possibly resulting from the precipitation of Si vacancies on dislocations. A detailed comparison of these results with those of Umakoshi, Sakagami, Hirano and Yamane (1990) was undertaken by testing material provided by Umakoshi along (001) at 1000, 1300 and 1400°C and along (771) at 1100°C at a strain rate of 1 × 10−5/s . Marked differences were observed and explained by the dislocation substructure observed after deformation.
Download or read book Initial Dislocation Structure and Dynamic Dislocation Multiplication in Mo Single Crystals written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Initial dislocation structure in annealed high-purity Mo single crystals and deformation substructure in a crystal subjected to 1% compression have been examined and studied in order to investigate dislocation multiplication mechanisms in the early stages of plastic deformation. The initial dislocation density is in a range of 106 (almost equal to) 107 cm−2, and the dislocation structure is found to contain many grown-in superjogs along dislocation lines. The dislocation density increases to a range of 108 (almost equal to) 109 cm−2, and the average jog height is also found to increase after compressing for a total strain of 1%. It is proposed that the preexisting jogged screw dislocations can act as (multiple) dislocation multiplication sources when deformed under quasi-static conditions. Both the jog height and length of link segment (between jogs) can increase by stress-induced jog coalescence, which takes place via the lateral migration (drift) of superjogs driven by unbalanced line-tension partials acting on link segments of unequal lengths. Applied shear stress begins to push each link segment to precede dislocation multiplication when link length and jog height are greater than critical lengths. This dynamic dislocation multiplication source is subsequently verified by direct simulations of dislocation dynamics under stress to be crucial in the early stages of plastic deformation in Mo single crystals.
Download or read book Dislocation Structures in Single Crystal Tungsten and Tungsten Alloys written by Joseph R. Stephens and published by . This book was released on 1969 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Dislocation Structure of Subboundaries in Molybdenum Single Crystals written by Feng Tuan and published by . This book was released on 1968 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using the etch-figure technique, the authors have directly observed the dislocation structure of subboundaries in electron-beam zone-melted molybdenum single crystals. A thorough analysis of experimental results are given. The authors have observed various patterns indicating interactions of singular dislocations with subboundaries, in particular, 'steps' on the subboundaries induced by singular dislocations and also interactions of inclusions with subboundaries. The etch-figure method of observing dislocations is an effective means for the quantitative study of dislocation substructure in crystals. (Author).
Download or read book Dislocation Mobility and Plastic Deformation in Molybdenum Single Crystals written by Gauri Charan Das and published by . This book was released on 1967 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Dislocations and Plastic Deformation written by I. Kovács and published by Elsevier. This book was released on 2016-07-08 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dislocations and Plastic Deformation deals with dislocations and plastic deformation, and specifically discusses topics ranging from deformation of single crystals and dislocations in the lattice to the fundamentals of the continuum theory, the properties of point defects in crystals, multiplication of dislocations, and partial dislocations. The effect of lattice defects on the physical properties of metals is also considered. Comprised of nine chapters, this book begins by providing a short and, where possible, precise explanation of dislocation theory. The first six chapters discuss the properties of dislocations and point defects both in crystals and in an elastic continuum. The reader is then introduced to some applications of dislocation theory that show, for instance, the difficulties involved in understanding the hardening of alloys and the work-hardening of pure metals. This book concludes by analyzing the effect of heat treatment on the defect structure in metals. This text will be of interest to students and practitioners in the field of physics.
Download or read book Dislocation Arrangements in Deformed Single Crystals of Niobium molybdenum Alloys and Niobium 9 At Rhenium written by R. A. FOXALL and published by . This book was released on 1970 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocation Substructures in Deformed and Recovered Molybdenum written by and published by . This book was released on 1961 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Specimens suitable for transmission electron microscopy were prepared from bulk polycrystalline molybdenum after tensile deformation and recovery. The resulting dislocation substructures are described. Some tentative conclusions concerning the mechanism of plastic deformation in molybdenum are discussed. (auth).
Download or read book Deformation Substructure in Deformed Ag A1 Hexagonal Single Crystals written by Paul Rokuro Okamoto and published by . This book was released on 1966 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Elastic plastic Deformation of Molybdenum Single Crystals Shocked to 12 5 GPa written by Anirban Mandal and published by . This book was released on 2016 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: The observed orientation dependence of the elastic wave amplitudes was understood by examining the corresponding resolved shear stresses (tau) on {110} and {112} slip systems determined from quasi-static studies. A comparison of the resolved shear stresses (tau el) on the operative slip planes at the elastic limit and the reported Peierls stress (tauP) for screw dislocations in Mo suggested that elastic wave amplitudes attenuate rapidly for tau > tau P, but no measurable attenuation occurs after tau ~ tau P. Resolved shear stresses corresponding to elastic limits under shock loading were ~10--50 times larger than the shear stresses under quasi-static loading, a likely consequence of the large Peierls stress in Mo crystals.
Download or read book Dislocation Substructure in Twisted Zinc Crystals written by Richard Franchere Tinder and published by . This book was released on 1958 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
