Folding in FCC metal single crystals under compression

Results of the analysis of folding during compression deformation of metals with fcc lattice are presented. Single crystals with orientations at angles of the standard stereographic triangle and different crystallographic orientations of lateral faces have been studied. It has been found that the major factor affecting the folding intensity is the slip plane shear with respect to lateral faces. Such a shear results in face bending and the formation of fold systems in maximum curvature regions. It has been shown that, among all considered orientations, the maximum susceptibility to the formation of different folds is inherent in single crystals with 1¯1¯ compression axis orientation. For this orientation, the development of shear and rotational components during folding is traced by interference microscopy and electron backscatter diffraction methods. It has been found that an excess dislocation density is accumulated when shear is activated in the folding region, which results in an increase in fold misorientation. The activation of this process in fcc metals is promoted by an increase in the homologous deformation temperature and stacking fault energy

Patterns of folded structure formation in the maximum bending zone of [111] FCC single crystals

Formation of folded structure in the zone of [111] FCC single crystals maximum bending has been studied on the example of nickel under compression tests. Quasi-periodical behavior of misorientation change in the folded structure has been established following the direction to increasing Schmid factor for the acting slip systems. Change in misorientation inside and on the boundaries of the formed folding coincides with its accumulation in dislocation system: inside and on the boundaries of deformation bands

Temperature dependence of the probability of "small heating" and total losses of ucns on the surface of fomblin oils of different molecular mass

We measured the temperature dependence of the probability of small heating and total losses of UCNs on the PFPE Fomblin Y surface with various molecular masses Mw=2800, 3300, 6500 amu in the temperature range of 100-300 K. The probability of small heating sharply decreases with increasing Mw and decreasing temperature. The probability of total loss weakly decreases with decreasing temperature and takes the minimum value at Mw=3300 amu. As this oil provides a homogeneous surface with minimal probabilities of small heating and total losses of UCNs, it is the preferred candidate for experiments on measuring the neutron lifetime

Segmentation effect on inhomogeneity of [110]-single crystal deformation

This work presents a detailed analysis of segmentation process in FCC single crystals with compression axis [110] and side faces( ̅110) and (001) considering effect of octahedral shear crystal-geometry and basic stress concentrators. Sequence of meso-band systems formation on side faces is determined. Macro-segmentation patterns are specified, that are common to the FCC single crystals under investigation. It is proved that rectangular shape of highly compressed crystals, elongated in direction of operating planes, is conditioned by orientation symmetry of compression axis, single crystal side faces and shears directions, which are characteristic for the given orientation. The specified patterns are characteristic only for the samples with initial height-to-width ratio equal to 2. When varying sample height relative to the initial one, segmentation patterns will also vary due to crystal geometry variations

Effect of initial microtopography and ultrasonic treatment mode on steel surface layer quality

The article presents results of studies on the effect of pre-lathed surface micro-relief on surface micro-hardness after ultrasonic plastic treatment, as well as the effect of ultrasonic treatment on structure and properties of surface layers of steels 20 and 40X. The effect of ultrasonic treatment processing modes on roughness and micro-hardness of the surface layers was studied. It is shown that roughness values as well as form of ridges and grooves, obtained by pre-lathing, effect the growth of micro-hardness values after ultrasonic plastic treatment

Quasi-specular albedo of cold neutrons from powder of nanoparticles

We predicted and observed for the first time the quasi-specular albedo of cold neutrons at small incidence angles from a powder of nanoparticles. This albedo (reflection) is due to multiple neutron small-angle scattering. The reflection angle as well as the half-width of angular distribution of reflected neutrons is approximately equal to the incidence angle. The measured reflection probability was equal to ~30% within the detector angular size that corresponds to 40-50% total calculated probability of quasi-specular reflection

Development of misorientation in FCC single crystals under compression at different scales

This article presents analysis of FCC single crystals local areas reorientation under compression. The reorientation process was examined at different scales, from sample size scale to that of dislocation substructure. It has been found that disorientation in meso and macro levels is determined by accumulation of misorientation at the level of dislocation subsystem. Our research allows quantifying of accumulated misorientation magnitude. The results of this study illustrate interrelation of rotational and translational deformation modes both at the same scale level and various scale levels

Comparison of mathematical methods of geochemical data processing

We have analyzed the data on concentration of geochemical elements within the 3- DV regional geochemical field. We have determined the fractal dimension index of spider diagrams and found the fractal nature of the distribution of chemical elements along the profile. We have compared these data with the results of the correlation analysis and hierarchical clustering methods. The agreement between the grouping of the elements according to the values of fractal dimension and the results of statistical analysis method was considered satisfactory