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

Influence of Lateral Incision on Inhomogeneous Deformation of a Nickel [001] - Single Cristal at Axial Compression

We used the scanning electron microscopy and the electron backscattered diffraction to investigate a deformation relief and a crystallographic disorientation of a nickel [001] single crystal with {100} faces with a lateral incision. We identified that the lateral incision can change the shear domains distribution pattern in the sample by creating additional deformation domains near the incision. The change in the patterns of the misorientation accumulation on the mutually perpendicular faces accompanies this deformation. We established that the orientation alteration occurs toward the increase of the Schmid factor for the slip systems in two of the four (previously equally loaded) slip planes. This method of shear deformation contributes to an optimal mutually consistent deformation in the adjacent areas of the single crystal

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

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

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

Octahedral slip in nickel single crystals induced by scratch testing

Investigation of the effect of crystallographic orientation on mechanical properties, behavior under loading, or deformation relief of single crystals is topical. One of the methods that make it possible to achieve unambiguous mutual orientation of the material structure and the applied load is scratch testing. This research is aimed at establishing the features of the deformation relief formation under various crystallographic conditions (orientation of the plane and scratch direction). The paper presents the experimental results on scratch testing on single crystals of nickel. The face of a single crystal (010) and two scratch directions [001], [–101] were investigated. The scratch testing parameters at which slip begins on the {111} planes have been determined. It is shown that the slip is activated most easily in the systems parallel to the direction of the indenter movement and in the systems oriented thereto at an angle of 45°. Three stages are identified on the scratch friction force vs normal load (F-N curve) and the correlation of the stages with the beginning of the shear traces formation is shown. The parameters of the transition to the third stage of the F-N curve and the magnitude of the friction force for scratch testing depend on the crystallographic orientation direction of the indenter movemen

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

The formation of a quasi-periodic surface profile by means of dislocation slip

This work presents the experimental results concerning the research of the morphology of the face-centered cubic (FCC) single crystals surface after compression deformation. Our aim is to identify the method of forming a quasiperiodic profile of single crystals with different crystal geometrical orientation. A set of modern methods as optical and confocal microscopy is applied. It is done to determine the morphology of surface parameters. The results show that the octahedral slip is an integral part of the formation of quasiperiodic profile surface and is starting with the initial strain. We present values of shear quantity directly in shear traces, meso- and macrobands and in shear tracks shift within them. The similarity of the process of surface profile forming at different levels of scale is given. Finally, we suppose that octahedral slip is the main way to form quasiperiodic deformation relief. We compare our results to published data and identify common regularities for various metal FCC single crystals with different deformation methods. The experimental results presented can be used for mathematical modeling of plastic deformation

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