Recently, several studies have focused on the crystallographic texture of bivalve mollusc shells. Unfortunately, these investigations have been limited to the local level. We demonstrate the similarities and differences between the texture measured over the whole shell and that measured over a small part of a shell. An analysis of the global crystallographic texture of bivalve mollusc shells of different genera was carried out using time-of-flight neutron diffraction. The reason for this analysis was to determine whether the crystallographic texture character was similar within the class Bivalvia. It was observed that the shells of mollusc species of the genus Mytilus consist of two phases, calcite and aragonite. Ostrea edulis shells consist of almost pure calcite, whereas Mya arenaria shells consist of almost pure aragonite. It was concluded that the character of the global textures of the different phases in the same shells is different. The advantages of characterisation of the global crystallographic texture are also discussed.
The aim of this work is to compare elastic properties of cubic materials with different texture types calculated with orientation distribution function (ODF) obtained by different methods: iterative series expansion method, Williams-Imhof-Matthies-Vinel (WIMV) and texture component method. We have used the approach of mean values for the calculation of elastic properties with different approximations (Reuss, Voigt, Hill). The calculations were carried out on a rolled Al-6% Mg alloy sheet and on an extruded Cu rod. The experimental pole figures were obtained by means of neutron diffraction and used for ODF calculation. The conformity between the different results is discussed.
Conventional procedures for quantitative analysis of retained austenite in steels by neutron diffraction ignore the effect of crystallographic texture and rely on apriori parameters rather than a direct calibration with appropriate etalons. As the main drawback, this method is not directly verified by independent data. In order to get over the verification problem, that is, to calibrate the method, reference sandwich-like samples with predefined amounts of austenite have been prepared. Neutron diffraction allows to measure large samples from one hand and to get rid of the texture influence from the other. Application of the proposed method was illustrated by volume fractions of retained austenite determination in medium-carbon martensitic steel tempered at various temperatures. Main result of our work is the developed method based on complete orientation averaging by means of neutron diffraction and usage of the calibration samples. It allowed to refine the austenite detectability limit to about 0.1% (vol.). Based on the method calibration, low fractions of retained austenite (0.13-2.9%) have been determined in the medium-carbon martensitic steel tempered at various temperatures.
Method to process neutron time of flight spectra for extracting texture information is suggested. Local peak fit is used to gain integral peak intensities as well as errors of fitted peak parameters. The usage of the method illustrated on spectra collected for Mg sample measured at Dubna on IBR-2 pulsed reactor at SKAT texture diffractometer. Reconstructed pole figures and corresponding errors are presented and discussed. It is important to underline that obtained errors are independent of the further method of pole figure processing.
View the article online for updates and enhancements. Abstract. In this work crystallographic texture for a set of rail wheel steel samples with different regimes of thermo-mechanical treatment and with and without modification by system Al-Mg-SiFe-C-Ca-Ti-Ce was measured by neutron diffraction. The texture measurements were carried out by using time-of-flight technique at SKAT diffractometer situated at IBR-2 reactor (Dubna, JINR, Russia). The three complete pole figures (110), (200), (211) of α-Fe phase in 5˚×5˚grid were extracted from a set of 1368 spectra measured for each sample. The samples were cut from rail wheel rim and from transitional zone (between rail wheel hub and wheel disk). It was concluded that the steel modification and some changes in the heat treatment modes of the rail wheels from the experimental (modified) and the conventional (non-modified) steel lead to reorientation of texture component. IntroductionSolid-rolled wheels for railway rolling stock are being currently produced by about fifteen industrial enterprises in different countries (Belgium, the Czech Republic, France, Russia, Ukraine, etc.). According to Railway Wheels and Wheelsets Committee (ERWA), global demand for wheels is about 4.8 million units per year. Passenger rolling stock market in Europe increases annually by 3% (according to the International Union of Railways). It is need about 500 kg of steel to make one rail wheel. The price of a steel increased since 2004 to 2010 by 100 -120%. The rising of a steel price leads to increasing of wheels price. Therefore, the important task for operating companies becomes to prolong life of wheels, and for producers of wheels is to use the most efficient ways of high-quality metal production. That is why the study of a rail wheel steel quality is urgent from both scientific and practical sides. One way to improve the quality of the wheels is a modification of the molten steel. The modification is admixture of small amounts of additives to modify the properties of alloy through a change its microstructure (grains size, grains shape) and prefered orientations, i.e. texture. The modifiers admixture result in grain refinement. Besides, the additional atoms incorporated into crystal lattice leads to its distortion. This process could result in the blocking of dislocations and consequently to alloy hardening. The final operational properties of the wheels depend on several factors, namely the chemical composition, the macro-and microstructure and also the crystallographic texture of the steel. The production technology of the rail wheels includes such operations as forging, press forming and rolling that can result in texture formation. The subsequent temperature treatment (annealing, quenching and tempering for rim) can also influence texture changing. The crystallographic texture can result in brittle cracking in steel products [1][2][3], so it can be one of the rail wheels damage reasons. The aim of this work is to study the impact of the modification and the thermo-mechanical treatmen...
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