Physics of Metals and Metallography (v.119, #7)

Peculiarities of Interactions of Alloying Elements with Grain Boundaries and the Formation of Segregations in Al–Mg and Al–Zn Alloys by M. V. Petrik; A. R. Kuznetsov; N. A. Enikeev; Yu. N. Gornostyrev; R. Z. Valiev (607-612).
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.
Keywords: Al alloys; grain boundaries; segregations; ab initio calculations

The Use of the Embedded-Atom Method in Statistical Thermodynamics of Metals by V. V. Zubkov; A. L. Isoyan; A. V. Zubkova (613-621).
An expression for the Helmholtz energy of a metal has been derived using the embedded-atom method (EAM) within the classical perturbation theory. An expression for the effective three-particle distribution function with effective three-particle interactions taken into account within classical statistical thermodynamics has been proposed. Temperature dependences of the atomic density and the internal energy have been calculated for copper and gold. These dependences have been used to analyze the effective EAM-derived potentials.
Keywords: embedded-atom method; thermodynamic perturbation theory; distribution function

Effect of Granular Spacer on the Exchange Bias Effect in FeMn-Based Film Structures by A. N. Gorkovenko; V. N. Lepalovskij; V. O. Vas’kovskiy (622-626).
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.
Keywords: multilayer films; granular microstructure; exchange bias; spacer; hysteretic properties

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.
Keywords: serve plastic deformation; magnesium alloy; microstructure evolution; ES process; recrystallization

The amplitude dependence of the internal friction (ADIF) of zirconium and Zr–8.1% Nb and Zr–20.2% Nb alloys has been investigated after different heat-treatment regimes. ADIF components caused by the processes of enhanced dissipation of energy at twin boundaries and at the boundaries of ω–β phases under mechanical vibrations have been revealed. The effect of twins, athermal, and isothermal ω phases, and the dislocation structure on the ADIF has been analyzed. A comparative analysis of the studied materials and their states in damping ability has been performed.
Keywords: zirconium; Zr–8.1% Nb and Zr–20.2% Nb alloys; heat treatment; amplitude dependence of internal friction; phase composition; martensite; α phase; ω phase; β phase; twins

Hydrogen in a Nonstoichiometric YBa2Cu3O6.96 Compound: Study by Raman Spectroscopy by I. B. Bobylev; Yu. S. Ponosov; N. A. Zyuzeva; P. B. Terent’ev (643-649).
Raman spectroscopy has been used to study the interactions between the YBa2Cu3O6.96 compound (123) and hydrogen at 150–200°C and their effects on the structure. It has been found that, when the YBa2Cu3O6.96 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 YBa2Cu3O6.96 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.
Keywords: HTSC; hydrogenation; Raman spectroscopy; structure

Structure of Al2Au Intermetallic Compound Obtained by Mechanochemical Synthesis by E. G. Volkova; A. Yu. Volkov; B. D. Antonov (650-659).
The structure of Al2Au intermetallic compound mechanically synthesized from a nanoscale gold powder and aluminum particles of about 0.5 mm in size has been studied by X-ray diffraction and transmission and scanning electron microscopy. It has been established that the intermetallic compound is formed as a powder with a particle size of 0.3–3 μm. In addition to intermetallic compound, some aluminum has been found in the powder, along with traces of gold and aluminum oxide Al2O3, and the appearance of an amorphous phase has been registered. The microstructure of compacts formed from the obtained powder has been studied, and heat treatments have been carried out. It has been found that compacting and subsequent annealing contribute to the agglomeration of intermetallic particles. Increasing the treatment temperature to 600°C results in the refinement of the structural elements as a result of their cracking in the surface layer. Compacts that are dark purple in their original state acquire a color ranging from pink to dark red as a result of annealing. After heat treatment, the presence of Al2O3, as well as of intermetallic phases enriched in gold (AlAu and AlAu4), has been detected in compacts in addition to the intermetallic compound Al2Au.
Keywords: intermetallic compound; mechanochemical synthesis; microstructure; electron microscopy

Metallographic Study of the Iron and Steel Articles Revealed in the Locality of the Former Kamensk Upper Plant by V. M. Schastlivtsev; B. A. Gizhevski; S. V. Naumov; Yu. V. Khlebnikova (660-668).
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.
Keywords: iron; carbon steel; chemical composition; technological modernization; metallography; X-ray diffraction analysis

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.
Keywords: plasma transfer arc welding; melt-in; key-hole; AISI430 stainless steel

Microstructural Evolution of Iron Based Alloys Produced by Spark Plasma Sintering Method by A. Muthuchamy; A. Raja Annamalai; M. Karthikeyan; Abhijeet Thakur; Nidhi Nagaraju; Dinesh K. Agrawal (678-684).
The effect of alloying additions, such as copper, carbon, and molybdenum with carbonyl iron powder, on the densification behavior, microstructural evolution, and mechanical properties of spark plasma sintered (SPS) compacts have been investigated in this work. The sintering temperature, pressure, and time during SPS were 1120°C, 30 MPa, and 5 min, respectively. Fe–2Cu–0.8C–0.6Mo was found to exhibit the highest density, hardness, and also tensile strength among all the compositions attempted. The microstructural examination of fractured surfaces of the sintered samples revealed the evidence of a mixed mode of fracture in all the alloy compositions.
Keywords: Keywords: powder metallurgy, field assisted sintering, SPS, density, mechanical properties, microstructural studies

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.
Keywords: aluminum matrix composite material; microstructure; scanning electron microscopy; EDS analysis; EBSD analysis; atomic force microscopy; nanoindentation; mechanical properties

Structure and Mechanical Properties of Steel Welding Joints Produced Using Abrasive Waterjet Cutting by T. I. Tabatchikova; S. V. Lepikhin; A. N. Morozova; N. Z. Gudnev (691-699).
The structure of welding joints of high-strength steel made using abrasive waterjet cutting has been studied using the methods of optical metallography and scanning electron microscopy supplemented with micro-X-ray spectral analysis. Uniaxial tension and impact bending tests with recording of loading diagrams were carried out on an impact tester. It is established that welding joints have satisfactory strength and toughness. A fractographic analysis of the fracture surface of ruptured and impact samples showed that the revealed defects are irrelevant to the presence of abrasive sand particles in the weld metal and weld-affected zone.
Keywords: steel; abrasive waterjet cutting; welding joint; weld-affected zone; strength; toughness; abrasive sand particles

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.
Keywords: Hadfield steel; doping with aluminum; structural transitions under friction; wear resistance