Vol 119, No 7 (2018)

The interactions between alloying elements and the symmetric edge boundary Σ5{210}[001] in Al alloys has been studied by the methods of the theory of the electronic-density functional. It has been shown that, in Al alloys, mechanisms of interactions of Mg and Zn with the grain boundary have been qualitatively different, which causes the peculiar morphology of the grain-boundary segregations. In the case of Mg, the deformational mechanism of interaction with the grain boundary is predominant, which facilitates the formation of relatively broad segregations. At the same time, in the case of Zn, the electronic mechanism, which is determined by directed chemical bonding, mainly contributes to interactions with the grain boundaries. As a result, it is more energetically advantageous for Zn atoms to occupy an interstitial position at the grain boundary or in the thin layer close to the grain boundary. The obtained results qualitatively explain the peculiar morphology of segregations at the grain boundary, which have been experimentally observed in the Al‒Mg and Al–Zn alloys.

The article deals with a study of interactions between permalloy layers separated by granular Со‒Al₂O₃ spacer. Multilayer Ta/FeNi/FeMn/FeNi/Co–Al₂O₃/FeNi/Ta films prepared by magnetron sputtering are the test object. The spacer thickness and content of metallic phase in the spacer have been varied from 0 to 8 nm and 0 to 40%, respectively. A correlation has been found between the Co concentration in the spacer and critical spacer thickness. When the thickness of the spacer exceeds a critical value, the independent magnetization reversal of the permalloy layers adjacent the spacer takes place. It has been shown that, in the case of both cooperative and independent magnetization reversal of permalloy layers, the presence of a spacer substantially affects the hysteretic properties of film structure. The data obtained can be useful when purposefully controlling the coercive force and exchange-bias field in film structures with the unidirectional anisotropy.

It is widely recognized that subgrain size has significant effect on the strength and ductility of metals. To improve the industrialization of the serve plastic deformations (SPD) technology for magnesium alloys, a new composite extrusion (shortened further as “ES”in this paper) has been employed. The components of ES die have been designed and manufactured and installed to the horizontal extruder for industry. The evolutions of microstructure and texture during the ES process have been studied. The results showed that fine and uniform microstructures can be achieved by Extrusion-Shear (ES) technique and a variety of types of texture can also be found in microstructures, which could weaken the dominant of base texture for (0002). From X-ray diffraction analysis it follows that the (0002) basal plane texture intensity has decreased, and there was found a continuous dynamic recrystallization happening during ES deformation. The research results showed that the ES process can produce a serve plastic deformation and improve the recrystallization of the grain and refine the grains,and weaken the dominant position of the base surface texture.

Raman spectroscopy has been used to study the interactions between the YBa₂Cu₃O_6.96 compound (123) and hydrogen at 150–200°C and their effects on the structure. It has been found that, when the YBa₂Cu₃O_6.96 compound is subjected to hydrogen intercalation and hydration, the transformation of 123 into tetragonal phase (pseudo-124) takes place. In this case, Raman spectra of the YBa₂Cu₃O_6.96 compound, similarly to those of a compound with absorbed water, exhibit antiferromagnetic fluctuations that are not typical of the compound. After hydrogenation, the 123 compound absorbs water under normal conditions and oxygen at temperatures below 300°C.

In this paper, we have continued a metallographic study of a number of old articles produced in the Urals at the beginning of the 18th century, i.e., during the transition from manual to factory production. The results of studying the microstructure and the chemical composition of articles made of iron and carbon steel at the Kamensk foundry and ironworks, as well the features of their production have been presented and discussed. This paper relates to the field of archeometallography.

In this study, AISI 430 stainless steel couple 10 mm thick were welded in the butt position by melt-in and key-hole plasma transfer arc welding (PTAW) processes without using any filler wire addition and pretreatment. Welded joints were manufactured choosing a constant nozzle diameter (2.4 mm), welding speed (0.01 m/min), shielding gas flow rate (25 L/min), two different plasma gas flow rates (0.8 and 1.2 L/min), three different welding currents in melt-in PTAW process (80, 85 and 90 A), and three current intensities of the key-hole PTAW process (120, 125, and 130 A). In order to determine the microstructural changes that occurred, the interface regions of the welded samples were examined by scanning electron microscopy (SEM), optic microscopy (OM), X-ray diffraction (XRD) after PTAW. Microhardness and V-notch impact tests were applied to determine the mechanical properties of the welded samples. In addition, fracture surface were examined by SEM after impact tests.

The microstructure and nanomechanical properties of the Al–7% Si–1% Fe as-cast alloy produced by blowing oxygen into the melt have been studied. Blowing oxygen into liquid aluminum alloy results in the formation of Al₂O₃ nanoparticles, which increase the strength of the alloy after subsequent cooling and crystallization. Scanning electron and atomic force microscopy (EDS and EBSD analyses) have been used to examine the microstructure of the Al–7% Si–1% Fe alloy. The nanohardness and Young’s modulus of α-Al in microvolumes are measured using nanoindentation. Blowing oxygen into the melt has been found to significantly decrease the random scatter of Young’s modulus of α-Al. The results have been considered through the lens of modern knowledge of how composite materials of the aluminum matrix are strengthened.

The structural transitions and tribological properties of carbon-containing high-manganese aluminum-doped austenitic steels tested under different dry-conditions of sliding friction have been considered. The methods used for the structural study of steels are metallography, X-ray diffraction analysis, and transmission electron microscopy. It has been shown that the doping of the studied steels with aluminum taken in the amount of 1.2 wt % significantly increases their resistance to abrasive wear, and especially adhesive wear (up to 20 times). It has been hypothesized that the observed positive effect of aluminum on the wear resistance of austenitic steels is due to the activation of the planar dislocation sliding mechanism, which increases the dispersion of nanocrystals and, correspondingly, the hardness of the surface layer of steels under the conditions of nanostructuring rotational strain by means of friction.