Thermodynamic properties of liquid alloys of the Ni-Hf system

By the method of calorimetry in isoperibolic conditions are determined integral and partial mixing enthalpies of liquid alloys of the Ni-Hf system at 1770 ± 5 K. Defined that liquid Ni-Hf alloys are formed with allocated large quantity of heat. The analysis of own and literary data has allowed to establish for mixing enthalpies of binary Ni-Hf liquid alloys dependence on temperature. With use of the Schröder equation are calculated the activities of studied alloys components from co-ordinates of liquidus line of the phase diagram of this system. Between calculated and experimentally established values of melts components activities of the Ni-Hf system is observed only qualitative consent. Are also calculated ΔG and ΔS of liquid Ni-Hf alloys.     

Interaction between copper and gallium

The interaction between solid copper and liquid gallium is considered, which is the main process during the setting of diffusion-solidifying solders. The dependences of the process rate and the size characteristics on the phase composition of the initial mixture are found. The intermetallic compound CuGa₂ is shown to be the product of the interaction in all cases.     

High-plasticity heat-resistant 03Kh14G16N6Yu-type steels with heat-and deformation-resistant austenite

The structure and mechanical properties of 03Kh14G16N6Yu-type austenitic steels alloyed by molybdenum, tungsten, vanadium, and zirconium are studied after normalization at 1075°C and long-term holding at 500–700°C. The chemical composition of these steels ensures the resistance of their austenite to the martensitic transformation in the temperature range from 1200 to ?196°C and during cold plastic deformation at a reduction of up to 60%. The best combination of the mechanical and technological properties is achieved in a 03Kh15G17N6YuVF steel with 0.08% W and 0.12% V. Long-term (up to 1000 h) holdings at 550–750°C do not cause the precipitation of carbide, nitride, and intermetallic phases in this steel. The long-term strength of the 03Kh15G17N6YuVF steel at temperatures up to 650°C is comparable with and its plasticity and impact toughness are higher than those of high-nickel Kh16N9M2 and Kh16N12M2 steels, which are applied in the main parts of electric power installations.     

Viscoplastic model for the strain resistance of 08Kh18N10T steel at a hot-deformation temperature

The viscoplastic model of the strain resistance of a metal developed earlier is shown to be applied to austenitic corrosion-resistant 08Kh18N10T steel with the fcc lattice at a hot-deformation temperature of 1150°C. Metallographic examination supports dynamic recrystallization occurring at this deformation temperature.     

Determination of matrix dependences between the magnetic and elastoplastic characteristics of steels during tension

Stress-strain and coercive force-strain diagrams are experimentally obtained for grade 45 and St3 steels. These diagrams are used to construct matrix dependences between the elastoplastic and magnetic properties of the steels in order to determine the level of stresses in construction members made of these steels.     

Aluminum hydroxide nucleation kinetics and mechanism during the electrodialysis decomposition of aluminate solutions

The kinetic laws of the electrodialysis decomposition of strong aluminate solutions are considered. Mathematical simulation is performed using the equations of the heterogeneous kinetics of aluminum hydroxide precipitation for the electrodialysis of aluminate solutions, and this simulation shows that the nature of the limiting stage is related to the instantaneous nucleation during the three-dimensional coalescence of particles. The electrodialysis precipitate is analyzed, and the possible commercial application of the decomposition of strong aluminate solutions by electrodialysis is considered.     

Chemical compatibility of a TiAl-Nb melt with oxygen-free crucible ceramics made of aluminum nitride

The problem of uncontrolled oxygen contamination of intermetallic TiAl ingots is considered for the application of crucibles and molds based on traditional oxide ceramics. A synthesized Ti-45.9Al-8Nb (at %) alloy is solidified in alternative oxygen-free crucibles made of high-purity aluminum nitride (99.99% AlN) upon holding at 1670°C for 5, 12, and 25 min and subsequent quenching in a high-purity argon atmosphere. The initial material and the solidified ingots are studied by scanning electron microscopy, optical microscopy, X-ray diffraction, electron-probe microanalysis, and gas-content chemical analysis. The key features of the interaction of the TiAl-Nb melt with AlN ceramics are revealed. Partial thermal dissociation of the crucible material according to the reaction AlN → Al + N and the reaction of atomic nitrogen with the melt lead to the formation of a solid 6.4-μm-thick TiN coating on the ingot surface and provide perfect wettability of the crucible by the melt and easy removal of solidified casting items from the mold. The TiN coating serves as a diffusion barrier that hinders the diffusion of nitrogen and residual oxygen from the pores in the crucible toward the melt. As a result, no oxide particles are detected in the ingots. However, few single microprecipitates of two nitride phases ((Ti,Al) _x N _y , NbN) are detected in the near-bottom region, 300 μm thick, in the alloy after holding at 1670°C for 25 min. The total oxygen contamination in a two-phase α₂ + γ ingot does not exceed 1100 wt ppm, which is 1.5–2 times lower than that obtained in the experiments performed with modern advanced oxide crucibles made of yttrium ceramics Y₂O₃. AlN is shown to be a promising crucible material that can be considered as an alternative to oxide ceramics in the metallurgy of TiAl intermetallics.     

Behavior of carbon,oxygen, and sulfur during hydrogen blowing of liquid steel

The decarburization of liquid steel during hydrogen blowing has been studied. The decarburization is caused by the interaction of carbon with oxygen dissolved in the metal. As the melt is blown with hydrogen, the decarburization is enhanced owing to hydrogen bubbles, which increase the effect of mixing of a metal bath and substantially increase the melt-gas phase interface. As a result, the rate and completeness of decarburization increase significantly. It is experimentally shown that hydrogen blowing of a melt substantially decreases the sulfur concentration in the metal because of the interaction of hydrogen with sulfur.     

Technological possibilities of manufacturing high-grade ferrotitanium from crude ore

The content of metal and oxide phases that form during aluminothermic melting of a mixture of ilmenite and rutile concentrates is studied by X-ray diffraction, electron probe, and metallographic analyses. The main components of the high-grade ferrotitanium melted from the crude ore are represented by the solid solutions of oxygen and iron in titanium and the Ti₄Fe₂O phase, which is not reduced to TiO₂. It has been shown experimentally that rich ferrotitanium (60–70% Ti) containing <5 wt % oxygen cannot be produced by the aluminothermic melting of the crude ore.     

Forward and backward creep during screw rolling

The common features of lengthwise rolling, cross rolling, and screw rolling (which is the most general case) are found. A mathematical model is used to obtain the values of velocity coefficients at any point in the deformation zone, to reveal the position of the neutral line and the conditions affecting the relation between forward and backward creep zones, and to find the cases where a forward creep zone is absent.     

Paraequilibria in the Fe-Si-C system and their relation to the bainite transformation in steels

The thermodynamic properties of silicon-containing cementite and ε carbide are estimated, and the results obtained are used to perform the thermodynamic calculation of paraequilibria in the Fe-Si-C system. Even a relatively low silicon content is shown to substantially change the positions of virtually all boundaries of phase fields in the Fe-C phase diagram. The relation between the paraequilibria and bainite transformation was analyzed. The maximum supersaturation of retained austenite is found to be controlled by a thermodynamic factor, namely, the solubility of the paraequilibrium cementite. The thermodynamic specific features also cause the differences in the mechanisms of carbide precipitation from the α and γ phases in the absence of silicon redistribution: only cementite can precipitate from austenite, whereas both cementite and ε carbide can precipitate from bainitic ferrite.     

Applicability of the laws of elasticity for the determination of the elastic-region length in the deformation zone during cold rolling

The errors of calculating the energy-force parameters of cold rolling are analyzed. They appear because of the assumption of the classic rolling theory about the applicability of the Hertz formula, which is known in the theory of elasticity, to the calculation of the elastic-region length in the deformation zone. The Hertz formula, which is used to calculate the half-width of the contact area between a fixed cylinder and a plane that bounds an elastic half-space, is shown not to take into account the following factors that are characteristic and important for the roll-strip contact: the cold working of the strip, the strip thickness, the rotation of rolls accompanied by sliding friction, and the wear that decreases the initial roll roughness (i.e., changes in the friction coefficient). A method is proposed for taking into account these factors in the calculation of the energy-force parameters of cold rolling; it is based on the statistical processing of the parameters that are measured in operating mills and are present in the databases of their process control systems. The application of this method decreases the errors of calculating the rolling forces by 35–40% and refines some laws of the state of stress in a rolled strip.     

Effect of alloying elements on the wetting of refractories by zirconium-and aluminum-based melts

The interface properties in refractory material-zirconium-or aluminum-based melt systems are studied by the sessile drop method. The effects of magnesium, yttrium, and lanthanum and the holding temperature and time on the wetting of quartz glass by these melts are analyzed. The crucible materials are chosen for Zr₆₅Cu_17.5Ni₁₀Al_7.5 and Al₈₆Ni₆Y₈ alloys, and the temperature conditions of their melting are established.     

Mechanism of the effect of the ferrite grain size on the fatigue strength of a low-carbon steel

The effect of the ferrite grain size on the fatigue strength of a low-carbon steel is studied. It has been shown that, as the ferrite grain size increases, the fatigue strength decreases due to plastic-flow localization. One of the explanations of this phenomenon is the beginning of the formation of periodical cellular dislocation structures.     

Processing of the rebellious polymetallic filizchai deposit ore using a combined technology

The results of studying the processing of rebellious polymetallic ores by a combined method are presented. The method combines the pyrometallurgical (pyrrhotinizing roasting) and hydrometallurgical (autoclave leaching with sulfuric acid) approaches. The proposed technology makes it possible to substantially enhance the degree of extraction of valuable components, simultaneously satisfying the requirements of the complex use of raw materials and the preservation of the environment.     

Atomic ordering in the phases of a nickel-chromium-based superalloy

The distribution of alloying atoms over the sites of the ordered crystal lattices of the γ′ phase and the Ni₂Cr superstructure that form during aging of the EK78 superalloy is determined by neutron diffraction, and their long-range order parameters are measured. The size, shape, and orientation of the forming γ′-phase precipitates and the ordered matrix are determined by electron microscopy. The mechanism by which the ordered phases in the EK78 alloy form during complex heat treatment is described.     

Role of silicon in the formation of the corrosion resistance of austenitic materials for cryogenic engineering

The effect of silicon on the operational efficiency and corrosion resistance of low-temperature equipment made of 12Kh18N12T chromium-nickel steel has been studied. The specific features of the cryogenic equipment consist in high-temperature heating procedures between operation periods. Equipment for gas liquefaction and cleaning aimed at the restoration of the operational efficiency of filtration and catalysis systems serves as an example. The heating temperature of this equipment can reach 800°C. Experimental steels containing 0.09–1.03 wt % Si are subjected to intercrystalline corrosion tests. Upon heating to 550–600°C, silicon is found to increase the corrosion resistance of the steel, and, upon heating at higher temperatures, silicon plays a negative role. This is caused by the distribution of silicon atoms along grain boundaries, namely, a nonuniform silicon distribution with the formation of high-and low-concentration regions, i.e., the formation of clusters of silicon-phase preprecipitates.     

Machinability of the high-strength corrosion-resistant high-ductility austenitic steel 06Kh22AG15N8M2F

The machinability of the high-nitrogen corrosion-resistant austenitic steel 06Kh22AG15N8M2F during turning is studied. The specific features of the structure of the surface layers in steel workpieces after turning are revealed. The cutting conditions that provide the lowest wear of VK8 alloy cutting tools upon turning are found: the cutting speed is 21–74 m/min, the feed is 0.15–0.60 mm/rev, and the cutting depth is 0.15–0.75 mm. The presence of a large amount of Cr₂N-type chromium nitrides in the structure of the steel annealed at 800°C for 2 h and a high nitrogen content in the austenite of the steel quenched from 1100°C increase the wear of the cutting tools. As to turning of the forged steel, the wear resistance of the cutting tools upon turning of the 06Kh22AG15N8M2F steel is higher than that upon turning of 08Kh18N10T steel, in which deformation martensite forms (in surface layers) during turning.     

Effect of the method of production of an Ni<Subscript>3</Subscript>Al/Mo layered composite material on its structure and properties

A stack of alternating 25 100-μ-thick Ni₃Al plates and 28 200-μm-thick Mo plates is subjected to hot isostatic pressing (HIP) at a temperature T = 1200°C and a pressure P = 150 MPa for τ = 2.5 h followed by hot rolling at 1050–950°C to a thickness of 2.3 mm. The stack is then subjected to cold rolling (CR) to a thickness of 0.5 mm without intermediate annealing, subsequent annealing during HIP at T = 1200°C, P = 150 MPa, and τ = 2.5 h, and CR to a thickness of 0.22 mm. Upon CR at a strain ε changing from 80.8 to 95.8%, the following specific structure forms in the longitudinal direction: molybdenum layers acquire a wavelike structure, can contact with each other, form “cells,” and retain almost the same thickness, and Ni₃Al alloy layers are rejected between the molybdenum layers to form a regular structure made of alternating thickenings and thinnings across the rolling direction. Annealing during HIP and subsequent CR to ε = 98.2% lead to the formation of zones with a broken alternation of layers in the longitudinal and transverse directions, which is related to different strain resistances of the (more refractory) molybdenum and Ni₃Al layers at 20°C. The adhesion between the layers is good, and no intermediate phases form at the interface. The ultimate bending strength of the 2.3-mm-thick workpiece at 20°C is 1000 ± 100 MPa, and the prepared material has a plasticity margin.     

Mechanism of the structure formation of the transition layers in cobalt films electroplated on copper

The structure formation of the transition layers in electrolytic cobalt films on copper substrates is studied. It has been found that epitaxial growth and repeated twinning in the transition film/substrate layers form the nonequilibrium α and β cobalt phases, which cause additional reflections in electron and X-ray diffraction patterns.