Thermal studies of Cr2O3 doped CaCO3-SiO2 (2∶1) system

Mixtures of CaCO₃SiO₂ in 21 molar ratio were subjected separated to thermal analysis with varying concentration of Cr₂O₃ (0.1 to 5%) as dopant. The activation energy (E _a) and enthalpy (H) shows a decreasing trend with 0.1 to 1% Cr₂O₃ and attains a minimum value with 1% dopant. 0.1 to 0.5% Cr₂O₃ helps in the formation of and C₂S, (Cement Chemistry notations, C = CaO, S = SiO₂) phases at 1400° C and above but 1% Cr₂O₃ stabilizes -C₂S phase along with a little free lime and CaCrO₄. A small quantity of CaCrO₄, Cr₂SiO₂ and -C₂S are also formed along with the major phases with 5% Cr₂O₃ indicating that Cr³⁺ can substitute both Ca²⁺ and Si⁴⁺ ions in the C₂S lattice.     

Effect of composition and porosity on the hardenability and hardness penetration of structural powder steels

Conclusions The effect of porosity ( > 10%) on the hardenability of the powder steels is stronger than the effect of carbon content. The role of these factors changes with the reduction of porosity ( < 10%) and the carbon content exerts a stronger effect on the hardenability of the steel. After hot pressing, the hardenability of the powder steels approaches the hard-enability of the dense steels of a similar chemical composition.The hardenability of the alloy powder steels at a constant carbon content and porosity is independent of the degree of alloying of the steel.The strength of the effect of complex alloying on the hardness penetration of the powder steels increases with decreasing porosity, especially after hot pressing and annealing as a result of the more efficient homogenizing of the structure with respect to carbon and alloying elements.Translated from Poroshkovaya Metallurgiya, No. 1(277), pp. 82–86, January, 1986.     

Effect of reduction temperature on some properties of ultrafine iron powders and hot-forged specimens

Conclusions A study was made of the processing properties of a reduced ultrafine electrolytic iron powder. The key parameter determining these properties is powder reduction temperature, which controls also the density of finished parts. An investigation into the process of structure formation during the heating of compacts for hot forging demonstrated the feasibility of producing -Fe of grain size 1 m or less. The principal parameters determining the conditions of production of an ultrafine -Fe grain are compact heating temperature and rate and duration of holding at the heating temperature. It is shown that ultrafine iron powders can be employed for manufacturing high-strength ultrafine-grained materials.Translated from Poroshkovaya Metallurgiya, No. 4(280), pp. 1–7, April, 1986.     

The effect of the amount of-phase on the vibration absorbing properties of powdered iron-manganese alloy

Conclusions A correlation was established between the content of -phase in the structure of the alloy Fe-Mn and its vibration absorbing properties. An increase of the amount of -martensite to 50–60% leads to an improvement of the vibration absorbing properties; when the content of -phase is further increased, the vibration absorbing properties deteriorate. To ensure maximal vibration absorption, the alloy has to contain 50–60% -phase. It was also cleared up what effect some heat treatment parameters have on the amount of -phase contained in the alloy.Translated from Poroshkovaya Metallurgiya, No. 12(288), pp. 52–55, December, 1986.     

Method of equivalent equations and the parameters of model intermolecular potentials

Using the method of equivalent equations we obtain improved (true) values for the parameters of the spherical shell potential for n-pentane.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 4, pp. 529–633, October, 1986.     

Measurement of the heterogeneous recombination probability of oxygen atoms in the course of supersonic dissociated gas flow interaction with solid body surfaces

A technique for determining time-resolved heterogeneous recombination probabilities

_W is developed which is based on comparison of the measured and calculated heat fluxes to a flat wedge-like plate set at a small expansion angle to a supersonic dissociated gas flow behind a shock wave with the typical parameters: pressure of 100 mm Hg, temperature of 3000 – 4000 K, and velocity of 2.5 – 3.0 km s^?1.