Origin of abnormal formation of pearlite in medium-carbon steel under nonequilibrium conditions of heating

The structure and kinetics of the formation of austenite in medium-carbon steel during shortterm heating above the temperature Ac₁ followed by accelerated cooling are analyzed. It has been shown that the abnormal formation of pearlite in steel results from the concentrational and structural inhomogeneity of austenite, as well as the presence of carbide particles in ferrite areas.     

Research on Thermophysical Properties of Nanoliquids Based on SiO<Subscript>2</Subscript> Nanoparticles for Use as a Heat-Transfer Medium in Solar-Thermal Converters

This paper presents an analysis of the modern state of studies of the thermophysical properties of nanofluids and the heat-transfer mechanism in them. The results of experimental studies of obtaining and determining the dynamic viscosity of the nanofluids (SiO₂ + water) with various concentrations of nanoparticles are given. Nanofluids are obtained using a two-stage method in an ultrasonic field with a frequency of 20 kHz. It is shown that, in the SiO₂ + water system, nanoparticles with sizes of 7, 12, and 16 nm are most stable. Various SiO₂ concentrations in the volume range 0.5–5% were tested, and their thermophysical properties were studied for the purpose of using them as a heat-transfer medium in flat-plate solar collectors.     

Molecular-Dynamics Simulation of the Influence of Silicon on the Ordering of Carbon in the Martensite Lattice

The results of computer simulation of the influence of silicon impurities on the degree of tetragonality and on the interaction of carbon atoms in the body-centered cubic (BCC) lattice of iron by the molecular-dynamics method are reported. The influence of silicon on the martensite-lattice parameters has been established, as well as the dependence of the deformation interaction parameter λ₀ determining the critical temperature of the BCC–BCT (body-centered tetragonal) transition on the silicon concentration, is calculated on the basis of the Zener–Khachaturyan theory of ordering. It is found that the λ₀ parameter decreases by 18% from 5.2 to 4.2 eV/atom upon an increase in the silicon content up to 10 at %.     

Two-sided bounds on the mean number of system failures during busy periods for various queueing disciplines

The expected number of system failures during the busy period Mv₁ is estimated for the M|G| 1 queue, assuming that the same failures occur in different queueing disciplines.Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 170–173, November–December, 1991.     

Role of stresses and temperature in the <Emphasis Type="Italic">Z</Emphasis> ordering of carbon atoms in the martensite lattice

A numerical solution is given to the equation of the statistical Zener theory of the predominant ordering of carbon atoms in the z sublattice of octahedral interstices of martensite in carbon steels depending on the stress and temperature. It has been found that the external compressive stress applied along the axis of martensite tetragonality decreases the order parameter and that there is a critical value of the stress above which the degree of tetragonality of the lattice falls off jumpwise to zero. Based on the numerical analysis, a discussion of the dependences of the degree of ordering of carbon atoms and the critical stress on the temperature and carbon concentration has been performed.     

The Formation of Carbide-Free Bainite in High-Carbon High-Silicon Steel under Isothermal Conditions

It is shown that a carbide-free bainite structure can be formed in high-carbon steel of the Fe–Si–Mn–Cr–V system using a traditional furnace facility. The structural aspects of bainitic transformation developing under isothermal conditions at 300°C have been studied by the methods of X-ray diffraction and transmission electron microscopy. Orientation relationships between crystalline lattices of γ and α phases have been established. A superequilibrium carbon concentration in the bainite α phase has been determined.     

Structural aspect of delamination crack formation during the HTMT of steels with a ferritic structure

The fine structure, texture, and fracture of the ferritic 08Kh18T1 steel subjected to repeated hot rolling at temperatures of 800–1100°C and reductions of 35, 50, and 65% have been studied. When significant strains are reached, a layered subgrain structure forms in the steel, and {100} and {111} planes are predominantly located in the rolling plane. The mechanisms of delamination crack formation during rolling under HTMT conditions are considered. The development of a crack in a material with a layered structure is analyzed theoretically.     

Transformation of austenite in Fe-Cu alloys. I: Kinetics of the transformation

The kinetics of autstenite decomposition in a hypereutectoid Fe-5.5% Cu alloy has been studied. Unusually large n values in the Avrami equation have been noted when using it for the approximation of experimental dependences. An explanation of this feature is given based on the hypothesis of a two-stage decomposition of the γ phase. An accelerating effect of hot plastic deformation on the austenite decomposition has been demonstrated.