Physical properties of the boride phases of chromium

Summary Certain physical properties (specific conductivity, thermal coefficient of electrical resistance, thermal conductivity, thermal, emf, Hall constant, melting point, microhardness) of the boride phases of chromium-Cr₄B, Cr₂B, CrB, Cr₃B₄ and CrB₂-were determined in this investigation.On the basis of the regular change in the physical properties of the phases with a change in the boron content, the conclusion is drawn that the nature of the chemical bond in the phases changes from the metallic for low boride phases to the covalent-metallic for higher phases.     

Plasma synthesis and physicochemical certification of chromium boride

Principles for the industrial plasma synthesis of chromium boride CrB₂ are developed. That entails analysis of the current state of its production and use; determination of the characteristics of the three-jet plasma reactor; simulation of the interaction between the raw-material and plasma fluxes; prediction of the characteristics of its synthesis on the basis of the simulation; selection of the optimal technology; implementation of the production technology; physicochemical certification of the chromium boride; and determination of the economic viability of the production process.     

Sintering of copper-tungsten materials

Conclusions To protect the Cu matrix of copper-tungsten compacts against hydrogen sickness, the starting compact porosity should be kept close to 20%. Resintering is accompanied by an increase in specimen volume, which grows with rise in tungsten content. The increase in volume is brought about by reduction-oxidation processes. No reaction has been observed between the metallic components of the system.Translated from Poroshkovaya Metallurgiya, No. 5(269), pp. 27–29, May, 1985.     

Sintering of Pr-Dy-Fe-Co-B materials

The properties of sintered magnets (Pr_{1 ? x} Dy _x )-(Fe_{1 ? y} Co _y )-B (x ? 0.6 at %, y ? 0.2 at %) as functions of the milling time and the sintering conditions are studied. Minima in the coercive force and the density as functions of the sintering temperature are detected. The dependence of the minimum depth on the milling time is detected. In the case of long-term sintering or additional sintering, the values of these parameters are restored. The minimum in the (Pr_{1 ? x} Dy _x )-(Fe_{1 ? y} Co _y )-B (x ? 0.6 at %, y ? 0.2 at %) materials is assumed to be related to the deceleration of diffusion processes in them as compared to the (Nd_{1 ? x} Dy _x )-(Fe_{1 ? y} Co _y )-B (x = 0.71 at %, y = 0.34 at %) system, in which this minimum is insignificant.