We investigate the corrosion resistance of amorphous zirconium-based alloys in a simulated biological fluid and in aqueous solutions of hydrochloric acid (with a HCl concentration of 0.1, 0.2, and 0.4 mol/L). Upon studying the effect of a simulated biological fluid, the samples are exposed to the medium in two ways. In the first case, the sample is completely immersed in a corrosive liquid. In the second, the sample is subjected to the local action of a drop of biological fluid deposited onto the surface. It is found that prolonged exposure to the medium leads to dissolution of the surface layer of the sample, while the local impact of drops does not affect the surface. The preliminary implantation of argon and nitrogen ions diminishes the effect of the simulated biological fluid on the samples. Polarization curves are obtained for all investigated alloys. In the curves obtained for alloys in a simulated biological fluid, the cathode and anode branches have a conventional form. The polarization curves for zirconium-based alloys in an aqueous medium with a HCl concentration of 0.1, 0.2, and 0.4 mol/L depend on the elemental composition of the alloys. In a sample without copper, the corrosion potential at different concentrations of HCl changes insignificantly. For a sample with a copper content of 15%, the corrosion potential shifts to the cathode region with an increase in the concentration of hydrochloric acid. The polarization curves of the sample with a high copper content (45%) are qualitatively different from the curves of the other samples. As in the sample with 15% of copper, the corrosion potential shifts to the negative region with an increase in the concentration of hydrochloric acid. The amorphous structure of the electrode material in zirconium-based alloys increases their corrosion resistance in comparison to the crystalline structure since the amorphous structure hinders the transition of the metal to the ionic state.

Impact of acidic solution with potassium rhodanide on partial electrode reactions was studied in AMAG-200 metallic glass (MG). Increase of acidity leads to growth of elec-trochemical reactions. With (mol/l) growth of potassium rhodanide in hydrochloric solution, radius of a circular Nyquist diagram increases that testifies to better corrosion resistance of AMAG-200 MG in mentioned environment. Surface coverage ratio of rhodanide-ions in-creases up to the 0.9-0.99 maximum with adding of potassium rhodanide. Because of the physic-mechanical features of the solution, surface co-adsorption of rhodanide-ions, Cl-, H3O+ ions, and HSCN, H2O molecules is possible that can lead to competitive adsorption, noticing in diagrams.

This work demonstrates a clear picture growth transition of aluminium nitride (AlN) films from the three-dimensional (3D) to the two-dimensional (2D) regime on the sapphire substrate at various temperatures using metal-organic chemical vapour deposition (MOCVD) under low reactor pressure. The high deposition rate of large 3D AlN islands that isolated each other change to 2D growth mode with a smoother surface as temperature increases from 800 ?C to 1340 ?C. From x-ray diffraction measurement, the AlN (100), AlN (002), and AlN (101) planes exhibit strong peak monocrystalline AlN (002) films as the temperature increase. It found that the AlN film grew at 1100 ?C in the Frank-van der Merwe or 2D growth mode exhibits the highest crystalline quality with the threading dislocation density around 2.21 x 10(9) cm(-2). In addition, the lattice vibrational parameters of the AlN films at 1100 ?C shows the lowest phonon damping from IR spectra results. Thus, this study details the AlN epitaxial films growth transition, which is crucial for growing high crystalline quality AlN layer using the MOCVD technique.

Abstract—To determine the cracking susceptibility for amorphous metal alloys (AMAs) or metallic glasses, a method based on the determining the dependence of the relative crack resistance (χ) on the load applied to intender of PMT-3 microhardness tester is proposed. In the method, the relative crack resistance at a load of 160 g is set equal to unit. At lower loads, crack resistance has been determined as the average of 10 measurements. In this article, we also have proposed a method for determining the heating temperature of AMA ribbons during laser beam machining that is based on a comparison of the dependence of the relative crack resistance of AMAs on load applied to indenter for samples annealed in the furnace and after laser irradiation. It has been found that cracks begin to appear in the samples after a ten-minute annealing at Т = 773 K. Fatigue tests of samples under a load varying from a maximum value of 750 MPa to a minimum of 400 MPa under a condition of repeated stress cycle with a frequency of 2 Hz have been carried out using a specially designed setup. In the domain exposed to laser radiation, four characteristic areas can be distinguished on the sample surface: internal reflow zone; dendritic growth area; area with unfinished growth of dendrites, area not exposed to radiation. In these areas, the relative crack resistance (χ) determined via the critical stress intensity factor of the first kind K1c monotonically decreases from 1 in the center to 0 at the periphery. It has been established that the laser action does not affect fatigue, the fatigue limit of the samples remains the same and is equal to 428 MPa. The characteristic features of the destruction are revealed. Cracks that propagate with branching in the reflow zone and after passing through its boundary develop rectilinearly have been found.

It has been experimentally established, that reversible electro-plastic effect, which is similar to the well-known case in crystalline metals, is observed on the σ(ε) diagrams for ribbon metallic glasses (MG). It has been established that passing of the impulse electrical current through the loaded specimen of MG leads to the larger fall of the mechanical stress than furnace heating at the same temperature. A linear relation between the fall of mechanical stress and temperature, depending on alloy composition, is observed. Growth of the duration of a current impulse at constant current density increases heating of the specimens with the larger reversible fall of the mechanical stress. Value of the reversible fall of mechanical stress, obtained with the impulses of electrical current in amorphous alloy, is caused not only by thermal expansion but also other reversible processes that are the result of the impact on amorphous alloys (for example, structural relaxation, that is reversible on the initial stage).

The structure and mechanical properties of ductile ferrite-pearlite 09Mn2Si steel after helical rolling (FIR) were studied. It has been shown that five passes of the helical rolling (with a gradual temperature decrease at each pass) resulted in a finely dispersed structure formation in the rod surface layer (up to 1 mm thick). This indicated the development of intensive plastic deformation there. At the same time, a lamellar structure consisting of thin elongated ferrite grains has formed in the underlying layers. The largest strain hardening was evident in the surface layer up to 3 nun thick. A yield tooth and plateau were evident on plastic flow curve. The length of the yield plateau was increased up to 2 times compared to as-received steel. This was accompanied with tensile strength increasing by 30%, while the elongation at break decreased. Data of cyclic testing have shown that fatigue life of the FIR-treated samples increased by 3.8 times. The highest fatigue durability was characteristic for specimens cut out from the core of FIR processed rod.

The effect of high temperature helical rolling (HR) on structure and fatigue life of 09Mn2Si pipe steel has been studied. With the use of transmission electron microscopy there was revealed that rolling gives rise to refinement of ferrite grains and cracking (fracturing) of cementite plates within the pearlite phase. The effect manifests itself to the greatest extent in the surface layer where due to the rolling the level of plastic deformation was the highest. Data of microhardness measurements confirms the gradient pattern of strain hardening over the cross section during the HR occurs while the most intensive microhardness increasing take place at the depth of up to 3 mm. According to the mechanical testing results the helical rolling of 09Mn2Si steel gives rise to increasing the level of deforming stress at the yield plateau as well as the proportionality limit with a general decrease in the relative elongation. At the same time, despite the strain hardening resulting from the helical rolling the mechanisms of plastic deformation which manifest themselves in the form of parabolic hardening with a smooth decrease in the flow stress level after neck formation are preserved in the steel. During the cyclic tension the number of cycles prior to failure increases from 2.5 to 3.8 times that depends on the location of specimens’ cutting from the rolled rod. The highest improvement in fatigue fracture resistance is registered for specimens cut out from the core of the rolled rods.

Effect of structure modification induced by the helical rolling on the impact toughness of 09Mn2Si steel was studied. A metallographic structural analysis of the steel in the as-received state as well as after the helical rolling (HR) was carried out. It was revealed that the five-stage combined thermal-mechanical treatment results in ferrite grains refinement, formation of rolling texture at the depth of up to 1 mm, while ultrafine grained structure is formed in the surface layer. This is accompanied by a gradient hardening pattern over the rod's cross-section as evidenced from microhardness measurements. Mechanical properties were assessed through impact bending tests. It is shown that helical rolling gives rise to increasing fracture toughness of the rolled specimens in the entire testing temperature range (-70 +/- +20 degrees C). The maximum two-fold increase of impact toughness is registered at the testing temperature of -70 degrees C. Authors suggest that the main reason for this increase is formation of a gradient fiber-like structure. The latter ensures effective arresting of the main crack growth during the impact bending.

Abstract The study on structure and mechanical properties of surfaced coatings and welded joints of 09Mn2Si steel formed with the use of a standard electrode as well as one modified by adding titanium carbonitride nanoparticles was carried out. Optical and scanning electron microscopy, microhardness measurement were employed to investigate the structure at welding with a standard electrode, as well as to illustrate changes resulting from the electrode modification through adding titanium carbonitride nanoparticles. Evaluation of mechanical properties was performed by conducting tests on static, cyclic and impact loading. It is shown that welding with the use of the modified electrode gives rise to decreasing the size of ferrite grains and increasing impact toughness and fatigue life.

Experimentally established the preliminary influence of hydrogen-containing medium (NACE) in cobalt-based amorphous alloys reduces the temperature of the onset of ductility during annealing. The structure of the surface changes forming in the holding of samples in the NACE medium either separate NaCl crystals or branched crystalline structures on the surface. A layer of oxide appears on the nanocrystalline alloy is preventing in heat exchange between the sample and environment. The passing of the impulse electric current j = 108 – 109 A/m2 results increases mechanical stress releases comparing to non-affected samples by the hydrogen-containing medium because of the temperature increase. The amorphous structure proves to be more resistant under simultaneous influence with the impulse electric current to the effect of the hydrogen medium NACE compare to the nanocrystalline one.

Studies on the impact of helical rolling on the structure and mechanical properties of 09Mn2Si pipe steel have been carried out. With the use of transmission electron microscopy it was revealed that the helical rolling gives rise to refinement of ferrite grains as well as fracture of cementite plates within the pearlite phase. This is particularly evident in the surface layer where the degree of strain resulting from the rolling achieved the maximum value. Microhardness measurements have confirmed gradient hardening pattern over the cross section of a rod being induced during the rolling. It is concluded that the most manifested increase of the microhardness takes place at the depth of up to 3 mm. Mechanical properties of the treated steel was estimated under static tension tests. It is shown that helical rolling of 09Mn2Si steel gives rise to increasing of the flow stress (at the yield plateau) and the proportionality limit, while the value of relative elongation has decreased. At the same time, despite of the strengthening induced by the helical rolling the strain hardening takes place in the steel. The latter is manifested through the parabolic hardening at the loading diagram followed by a gradual decrease in the flow stress after the neck formation.

The authors carried out the fatigue tests for the tension of metallic glass tape samples by the load varying in time from some maximum value to minimum, in a constant-sign cycle with the frequency of 2 Hz. In the device construction, five sets of elastic elements with different stiffness coefficients are designed. For the elastic elements, the calibration graphs were constructed, according to which the stress in the sample was determined by the displacement value. Characteristic features of the development of fatigue cracks in the samples of cobalt-based amorphous alloys and iron-based nanocrystalline alloy were determined. The study determined the area of the fatigue crack nucleation, its growth and the break area. It is identified that the viscous destruction with the formation of densely spaced microtights takes place in the area of crack initiation, and in the area of the fatigue crack growth, its development similar to a cleavage with the formation of the developed “venous pattern” and the densely spaced shear bands formed when fatigue cracks stop occurs. The pop-in magnitude is 0.2-0.5 pm. In the break area, the crack propagates viscously, irregularly, with the formation of localized plasticity areas at the stops. For the samples, Weller curves are plotted and the fatigue limits are defined. The authors carried out the investigations of the aggressive environments influence and the pulsed electric current preliminary impact on the fatigue properties of the amorphous metal alloys. It is determined that the samples, after the action of a pulsed current or an aggressive environment, are destroyed during fewer loading cycles relating to the initial samples. It is noted that the Co content in the samples under the study slightly influences the fatigue properties.

Catalysts based on transition metal oxides are the most promising for the efficient combustion of fuel in a fluidized bed. Afterburning coke is a limiting stage of fuel combustion, characterized by the release of carbon monoxide (CO) and its reacting with oxygen on the catalyst surface. Determination of the observed kinetic parameters of this process will further evaluate the efficiency of the catalyst, and optimize the performance of fluidized bed reactor. The study of the kinetics of CO oxidation on the industrial catalyst SCHKZ-1 (oxide aluminum-copper-chromium), currently used in the fluidized bed reactor when burning fuels. The studies carried out in conditions when the internal diffusion does not affect on the reaction rate. Kinetic parameters of the reaction were evaluated by a first order equation for CO and O2; the obtained values of activation energy and pre-exponential rate constants were respectively ko = 5,23·107 s–1, E = 32,8 kJ/mol. A comparison with published data showed their good correlation .

The durability of the metal structure of a clamshell crane is predicted in two ways: by the hypothesis of linear summation of damage and using the model of cyclic degradation of the static properties of the material. In the second case, a conservative estimate of longevity is obtained for a quasi-random stress spectrum at the dangerous point of the span beam. A significant influence of structural damping on the service life of the crane has been revealed. Calculations by the developed algorithm are performed on an ordinary personal computer with a small expenditure of computer time.

The structure, mechanical properties and deformation behavior of welded joints of 17Mn1Si pipe steel modified by means of surface ultrasonic impact straining and combined pulsed mechanical-electrophysical treatments have been studied. Welded steel plates of 10 mm thickness were used for specimens' preparation. In doing so, their gauge length comprised of the heat affected zone and directly the weld region. It is shown that the proposed treatment techniques provide hardening of the surface layer, as well as increase in tensile strength. The revealed differences in the structure modification and deformation behavior of the specimens subjected to different treatment methods are illustrated and discussed.

The harmful emissions from traditional organic fuels combustion cause irreparable harm to the environment, which leads to the conclusion that it is necessary to reorient the energy sector to renewable energy sources such as biomass. Traditional methods of combustion are of little use for the energy use of biomass. This fact forces us to search new efficient technologies for its processing. Pyrolysis is one of the most universal and promising areas of biomass processing. However, its implementation requires significant heat costs, which has a considerable impact on the result of the feasibility study. The aim of the work is to study the thermal effects observed in low-temperature pyrolysis and to assess the possibility of autothermal biomass processing. Straw, chips from various types of wood, pine sawdust and peat from two deposits of the Tomsk region (Russia) were considered as a biomass. A physical experiment, differential thermal analysis, gas chromatography and heat balance equations were used in the work. It has been established that low-temperature pyrolysis of biomass is accompanied by a positive value of the thermal effect in the temperature range of 220–580 °C and varies from 393 to 1475 kJ kg−1 depending on the type of raw materials being processed. The value of this effect makes it possible to organize pyrolysis of biomass in an autothermal regime with preliminary drying: maximum moisture content for straw of 19.9%, wood chips of 10.4%, sawdust of 9.7% and Sukhovskoy peat of 9.5%.

We study the morphological features of laser irradiation zones formed on the surface of the bulk metallic glasses. We use the nanoindentation method for estimation alloys properties caused by impulse heating during irradiation.

Relaxation processes in amorphous and nanocrystalline alloys in temperature range of –196 ÷ 80 °C have been studied. It was established that in amorphous alloy stress relaxation occurs in two stages. At the same time, decrease in initial mechanical stress in the sample by 5 % only occurs during the holding time of at least 1 hour. An increase in temperature of the sample leads to more intensive relaxation, which is manifested in an increase in rate of mechanical stress decrease. At the temperature of liquid nitrogen, stress relaxation is not observed. It has been established that in nanocrystalline alloy relaxation processes proceed in a similar manner, but relaxation rate is much lower. Dependences of residual mechanical stress on temperature and holding time were studied. It was found that in amorphous and nanocrystalline alloys, areas of stabilization of residual mechanical stresses are observed at small holding time (less than 5 min) in temperature ranges of 50 – 60 and 40 – 50 °C. Increase in holding time leadsto monotonousfall in residual mechanical stresses. Heating up to 40 °C results in complete relaxation of mechanical stresses in the sample 15 minutes after the start of the testing. It is shown that preliminary relaxation of stresses in amorphous alloy leads to decrease in value of mechanical stress relieving during electropulse ipmact in samples subjected to stretching. In nanocrystalline alloy, value of relieving remains practically unchanged under the indicated impact. It is also shown that the observed effect occurs due not only to thermal expansion, but also to change in the value of reversible component of directed structural relaxation. In the course of work it was established that value of mechanical stress relieving in amorphous alloy depends on medium in which electric current impulse is supplied. In particular, in liquid nitrogen medium, decrease in value of relieving is observed. Such a decrease is not observed in nanocrystalline alloy.