SCIENCE & EDUCATION

 The authors study the effect of welding heat to corrosive properties of maraging steel, the influence of chemical composition of steel on liability to intergranular corrosion; they set a method of improving corrosion resistance of welds by use of surface treatment.

The authors give an analytical review of the work related to researches of influence of electromagnetic fields on the structure and properties of materials (dia-, para-and ferromagnetic). The authors provide a classification of effects caused by magnetic fields (constants, variables, pulse) and give classification methods of magnetic material processing. The authors compare the most significant results in this area and summarize prospective mechanisms of interaction of the magnetic field with materials.

The regression dependence of the carbon and nitrogen potential on the acetylene temperature and concentration at saturation of iron and complex-alloy steels in glow discharge plasma was determined. The defining influence of the adsorption rate of acetylene molecules on the intensity of carbon mass transfer was revealed. The most probable reaction of acetylene dissociation was determined according to the analysis of experimental data, thermodynamic calculations and the structure of the acetylene molecule. The influence of the solid solution and the reaction mechanisms of saturation on the mass transfer kinetics of carbon during ion carburizing were described.

The authors analyzed the existent doping techniques for titanium filler wire with the usage of oxygen for welding deposition of hardwearing coatings onto the surface of titanium parts by means of nonconsumable electrode arc welding. Equipment for micro-arc oxidation of welding titanium alloy wire was developed; it allows to regulate oxygen content in the welding wire smoothly and, therefore, the deposited metal hardness along with automation of doping the wire with oxygen and the following welding deposition.

The authors consider a method of improving antifriction properties of surfacing of titanium alloy parts. Technological operations of thermal and micro-arc oxidation methods aimed at surfacing the wire with stable oxide layer development are compared.

This article deals with the results of a thermodynamic analysis of nitrides phase state, their quantity in the alloy HA30-VI when the quantity of nitrogen varies in the initial furnace-charge at different melting stages. Thermodynamic calculations allow to estimate the phase composition of liquid melt and crystal nickel alloy HA30-VI. It was investigated whether titanium nitride, hafnium and carbides in equilibrium conditions were part of that alloy. Minimal permissible quantity of nitrogen required to eliminate the formation of nitrides was calculated.

Nitrogen behavior under different thermo-time modes of the melting alloy HA30-VI in the induction furnace was investigated; optimal temperature of melted nitrogen depuration was determined. The negative influence of nitrogen on the formation of parasitic grains with random orientation near the surface of mono-crystal casting was shown. Non-uniform distribution of nitrogen with the height of cast mono-crystals was determined.

This article is a review of up-to-date techniques of enhancement of abrasive wear resistance of materials. It was shown that heterophase composite structures are the highest wear resistant ones. The article deals with methods of wear resistant coatings. The influence of gas mixture composition on overlays’ structures and properties was considered. The data on hydroabrasive wear of arc welded composite coatings was given.

In the framework of the density functional theory ab initio calculations of free energy at 0 K, electron density and magnetic moments were performed for Pd-Mn and Cu-Mn spin glasses. It was assumed, clusters consisting of two, three or four Mn ions existed in solid solution thus forming dumbbells, triangles or tetrahedrons respectively. Clusters stabilize solid solutions in all cases, while the magnitude of the magnetic moment is dependent on the cluster structure. In Pd-Mn solutions the highest value of the giant magnetic moment per Mn ion (7,2 Bohr magnetons) corresponds to Mn tetrahedron with the sequences of Mn-Pd-Pd-Mn as the tetrahedron edges. In Cu-Mn solutions the highest value of the giant magnetic moment (4,2 Bohr magnetons) corresponds to a single Mn ion. It was established that fields of solid solutions in Pd-Mn and Cu-Mn systems corresponded to the states of the colloidal solid solution.

The authors studied the influence of annealing temperature and degree of cold plastic deformation on the phase-structural condition of alloy V-4Ti-4Cr. By the changing of the lattice period of the vanadium solid solution it was shown that the increase of the annealing temperature to 1400 °С resulted in dissolution of vanadium primary oxicarbonites. Subsequent deformation allows to raise the hardness of the alloy more than twice at the expense of stress aging. Besides, it was revealed that at the degrees of deformation more than 40%, the mechanism of deformation in alloys changes from dislocation to twin.

An experimental study of carbon and nitrogen saturation of complex-alloyed steel in low-pressure atmosphere was conducted. After the process of vacuum nitrocarburizing the quantity of austenite was increased. Also the dimensions of carbonitride particles were decreased. The control factors of vacuum nitrocarburizing technology were optimized with use of a mathematical model.

This paper presents an analysis of scientific information on the experiments carried out in the field of laser doping of aluminum alloy surfaces with various components in a wide range of treatment modes with different types of lasers. The authors analyzed laser alloying of aluminum alloys with non-metallic components, laser alloying of aluminum alloys with metallic components and laser alloying of aluminum alloy with compounds. It was found that laser alloying of aluminum alloy with metal components, their mixtures and alloys increases surface performance. A distinctive feature of the structure formation of doped zones of aluminum alloys is high satiation of solid solution which exceeds solubility under equilibrium conditions as well as formation of intermetallic compounds. It is shown that there is a real possibility of laser hardening of aluminum alloys: by changing the parameters of the surface treatment with a pulsed or continuous laser beam one can control the characteristics of doped zones, such as size, concentration, saturation components, structure, and microhardness.

The authors show the existence of special polyhedra (clusters) and combinations of polyhedral, which are the structural implementation of algebraic geometry constructions. An algorithm of graph derivation corresponding to a special class of simple polyhedra with 24 vertices and 14 faces was considered for the case when these polyhedra have 4-, 5- and 6-gonal faces. The graph was derived for the first time for the polyhedron with one tetragonal face and which is not a parallelohedron. Polyhedra of this class allowed to determine the possibility for 14-verticed canonic and non-canonic Frank-Kasper polyhedra to be presented in the structure of intermetallics. This approach allowed to determine the symmetry of wide spectrum of ordered (not necessary crystalline ones) tetra-coordinated (diamond-like, clathrates) and tetrahedral (metallic) structures larger, including also nanostructured states.

Experimental studies of bond strength using the standard method of GOST1497-84 on titanium alloy specimens (Ti6Al4V) were conducted. The crack was simulated on the samples, then it was cladded using laser treatment and determined the destructive load for each sample. According to test results the optimal cladding parameters were chosen so that mechanical properties of the specimen with a cladded crack practically did not differ from the intact sample (the value of the destructive load for cladded sample was Pmax = 62,8 kN, while for the intact sample Pmax = 63 kN). Failure occured far from the cladded area.

The symmetry of a clathrate crystal can be adequately displayed within the apparatus based on constructions. The apparatus of algebraic geometry and topology was proposed for fundamental description of tetrahedral and tetra-coordinated structures. Such a description allows to represent any structure as a combination of helices (rods) consisting of polyhedrons i.e. cavities of clathrates or coordination polyhedrons of intermetallic semiconductors. The crystal lattice can arise only as a variant of such a combination. Crystal structures of clathrates (gas-hydrates and intermetallic semiconductors) are described as a combination of helicoids with nonintegral swivelling axes 10/3, 12/5 и 15/4. The structure of clathrate IX (Ba24Ge100) for the first time was determined as dual to the β-Mn structure.