Study of the influence of the parameters of an experiment on the simulation of pole figures of polycrystalline materials using electron microscopy

2016 ◽  
Vol 61 (3) ◽  
pp. 523-531 ◽  
Author(s):  
A. O. Antonova ◽  
T. I. Savyolova
Author(s):  
K. J. Morrissey

Grain boundaries and interfaces play an important role in determining both physical and mechanical properties of polycrystalline materials. To understand how the structure of interfaces can be controlled to optimize properties, it is necessary to understand and be able to predict their crystal chemistry. Transmission electron microscopy (TEM), analytical electron microscopy (AEM,), and high resolution electron microscopy (HREM) are essential tools for the characterization of the different types of interfaces which exist in ceramic systems. The purpose of this paper is to illustrate some specific areas in which understanding interface structure is important. Interfaces in sintered bodies, materials produced through phase transformation and electronic packaging are discussed.


2020 ◽  
Vol 53 (2) ◽  
pp. 561-568
Author(s):  
Rui-Xun Xie ◽  
Wen-Zheng Zhang

τompas (TEM online multi-purpose analyzing system) is a free and integrated software tool designed to perform online crystallographic analysis in transmission electron microscopy (TEM) experiments. By using sample holder tilt angles as input, τompas can simultaneously simulate pole figures, Kikuchi patterns and feature projections, providing graphical views of the sample crystallography. These simulations are further employed to navigate sample tilting and to quickly interpret experimental Kikuchi patterns and images by image matching, giving self-consistent indices of features and crystal orientations. These functions are integrated with mouse operations to improve work efficiency. τompas is distributed as a small cross-platform program that can be installed on a microscope computer to cooperate with other tools.


1988 ◽  
Vol 10 (1) ◽  
pp. 67-75 ◽  
Author(s):  
M. Wróbel ◽  
S. Dymek ◽  
M. Blicharski ◽  
S. Gorczyca

The initial orientation has split into two equally strong symmetric orientations: (112)[111¯] and (112)[1¯1¯1]. Areas of identical orientation were band shaped and were called deformation bands. Up to 60% reduction, deformation occurs by slip on one plane (one from two possible) in two directions. This leads to the appearance of deformation bands with transition bands between them. Due to such deformation the initial orientation rotates around transverse direction towards the end-orientation {112}〈111〉. Due to rotation of the crystallographic lattice with deformation, the Taylor factor M changes as well, and it causes the activation of two not coplanar slip systems which stabilize the end-orientations {112}〈111〉. Such a sequence of the slip systems activation was concluded from the agreement of the calculated and experimental pole figures. The electron microscopy investigations showed that first shear bands formed due to the activation of these new slip systems.


2000 ◽  
Vol 6 (S2) ◽  
pp. 188-189
Author(s):  
M. Rühle ◽  
C. Elsässer ◽  
C. Scheu ◽  
W. Sigle

Most materials used in technology are polycrystalline. Therefore, the properties of the internal interfaces often control the properties of the materials (interface-controlled materials). In single phase polycrystalline materials, grain boundaries are the internal interfaces (homophase boundaries) of interest, whereas in composites interfaces between different components (heterophase boundaries) play a crucial role. It is of great importance to investigate the structure, composition and bonding of the different interfaces. The atomistic structure of specific interfaces is obtained by high-resolution transmission electron microscopy studies, whereas analytical electron microscopy (AEM) investigations produce information on the composition of interfaces. AEM studies include energy-dispersive X-ray spectroscopy (EDX) as well as electron energy-loss spectroscopy (EELS). From the energy-loss near-edge structure (ELNES) of ionization edges measured by EELS, information on the local electronic structure at interfaces can be obtained. Information on bonding and its modifications by segregated atoms can be extracted from the ELNES studies.


2019 ◽  
Vol 85 (9) ◽  
pp. 46-51
Author(s):  
A. V. Stepanenko

The results of studying correlation between the crystallographic texture of polycrystalline materials and anisotropy of their physical and mechanical properties are considered. The methods for calculating the anisotropic properties of polycrystals based on the data obtained by X-ray methods of direct and inverse pole figures are reviewed. Calculation methods based on the use of the distribution function of crystallite orientations require the use of a large amount of experimental data and, hence, they are not suitable for express estimation of the anisotropy level of the physical properties of samples upon their thermomechanical processing. A method for rapid estimation of the anisotropic properties of the sample based on the use of Д; ("orientation factors") in the calculations, is proposed. Experimental data of X-ray analysis (method of inverse pole figures) are used to calculate the absolute and relative deviations of the physical parameter of textured polycrystal from the same value in the isotropic sample. The contributions of individual crystallographic orientations to the formation of the anisotropy of the properties of the sample are estimated. The dynamics of quantitative changes in the anisotropic properties of a polycrystal in the process of texture formation is studied. To analyze the source of the most rapid changes in the anisotropy of properties, we used the coefficients of the "response" matrix, the calculation of which does not depend on the results of specific diffractometric measurements, but is common for all metals with a hexagonal close-packed (hep) lattice. The anisotropy of the coefficient of thermal conductivity, electrical conductivity, and thermal diffusivity was calculated for the samples of deformed yttrium which underwent cold rolling with a reduction ratio of e = 25%. It is shown that the final physical properties_of the hep polycrystal are largely determined by the pyramidal crystallographic orientations {1015}, {1124}. The results of the study form a basis for analysis of the anisotropy of the physical properties of hep-metal samples upon thermomechanical processing.


1989 ◽  
Vol 156 ◽  
Author(s):  
H.W. Zandbergenl ◽  
G. van Tendeloo

ABSTRACTHigh resolution electron microscopy has been carried out on grain boundaries in a number of superconducting oxides: YBa2Cu3O77−∂, LaCaBaCu3O7−∂, Bi2Sr2CanCun+1O2n+6+∂, and Pb2(Sr, Ca)3−xAxCu2+nO6+2n+∂. In general no amorphous material or another phase is observed at the grain boundaries. It is argued that the low critical currents in these polycrystalline materials are caused by the atomic structure of (001) interfaces at grain boundaries and concerning YBa2Cu3O7 and LaCaBaCu3O7−∂ by the intercalation of CuO layers starting from the grain boundaries.


1999 ◽  
Vol 33 (1-4) ◽  
pp. 337-341
Author(s):  
T. I. Savyolova ◽  
E. A. Davidzhan ◽  
T. M. Ivanova

Macroscopic physical properties of most polycrystalline materials are controlled by orientation distribution of their grains. The orientation distribution function (ODF) of a polycrystal is seldom if ever determined directly from an experiment. Usually experimental data are represented by a set of pole figures (PFs), these latter are some integral projections of the ODF. The main problem of quantitative texture analysis is to recover ODF from its corresponding PFs. With any set of PFs the solution of this problem is non-unique. That is why some assumptions about ODF structure are necessary. We consider ODF as superposition of the canonical normal distribution (CND) on the rotation group SO(3).


1992 ◽  
Vol 25 (2) ◽  
pp. 259-267 ◽  
Author(s):  
M. Dahms

The orientation distribution function (ODF) of the crystallites of polycrystalline materials can be calculated from experimentally measured pole density functions (pole figures). This procedure, called pole-figure inversion, can be achieved by the series-expansion method (harmonic method). As a consequence of the (hkl)-({\bar h}{\bar k}{\bar l}) superposition, the solution is mathematically not unique. There is a range of possible solutions (the kernel) that is only limited by the positivity condition of the distribution function. The complete distribution function f(g) can be split into two parts, \tilde {f}(g) and \tildes {f}(q), expressed by even- and odd-order terms of the series expansions. For the calculation of the even part \tilde {f}(g), the positivity condition for all pole figures contributes essentially to an `economic' calculation of this part, whereas, for the odd part, the positivity condition of the ODF is the essential basis. Both of these positivity conditions can be easily incorporated in the series-expansion method by using several iterative cycles. This method proves to be particularly versatile since it makes use of the orthogonality and positivity at the same time. In the previous paper in this series [Dahms & Bunge (1989) J. Appl. Cryst. 22, 439–447] a general outline of the method was given. This, the second part, gives details of the system of programs used as well as typical examples showing the versatility of the method.


1968 ◽  
Vol 12 ◽  
pp. 404-417 ◽  
Author(s):  
C. Richard Desper

AbstractThe Picker Four-Angle Computer System (FACS-1), a computercontrolled x-ray diffractometer originally designed for single crystal studies, has been adapted for use with polycrystalline samples. The system is controlled by a PDP-8S, a small time-sharing computer with teletype input and output. Programs have been written to take advantage of the high degree of flexibility inherent in online computer control. Four basic operations are possible: (a) simple 2θ step-scanning with variable step width; (b) 2θ stepscanning with randomization of orientation; (c) determination of Legendre expansion coefficients for oriented specimens; and (d) determination of pole figures. In operation (a), data is gathered at a series of 2θ values at a prefixed count and/or time. In (b), the sample is rotated to average out orientation, giving the “randomized” intensity (2θ) at various 2θ values. The on-line computer reads the scaler and timer every two degrees of x rotation and forms the appropriate integrals for calculating (2θ) as the sample rotates. Operation (c) is an extension of (b): not only is (2θ) determined, but also various moments of the orientation distribution of the form , where Pn is the nth order Legendre polynomial. Operation (d) may be used to measure pole figures of sheet specimens in reflection or transmission, or of fibers or small particles. Optional modes of operation allow for (a) use of the Ross “balanced filter” technique; (b) integration across diffraction peaks by continuous scanning in 2θ, with background correction; and (c) application of absorption corrections.


2010 ◽  
Vol 09 (06) ◽  
pp. 549-552
Author(s):  
AYACHE RACHID ◽  
BOUABELLOU ABDERRAHMANE ◽  
EICHHORN FRANK

The processes in the synthesis of a thin layer of hexagonal YSi 2-x phase on a single-crystal Si (111) substrate by implantation of 195 keV Y ions with a dose of 2 × 1017 Y +/ cm 2 at 300°C followed by annealing in an N2 atmosphere at different temperatures for 1 h are investigated. The characterization of the as-implanted and annealed samples is performed using Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD) pole figures. Scanning electron microscopy (SEM) was used to view the surface topography. The results show that the orientation relationship between the YSi 2-x layer and Si substrate is YSi 2-x(0001)// Si (111) and YSi 2-x[11–20]// Si [110].


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