Boundaries of the single-phase side fields of the system Mo-Cu-Ni in the solid state

Conclusions It was established that the molybdenum corner of the Mo-Cu-Ni ternary system contains a singlephase field of solid solutions of copper and nickel in molybdenum with a combined Cu and Ni content of 1.5–2 wt.%. At the copper-nickel side of the constitution diagram of this system, there is a single-phase field of ternary Cu-Ni-Mo solid solutions, whose molybdenum content steadily rises with increase in nickel concentration, from 1.5 wt.% at NiCu=2080 to 3 wt.% at NiCu=4060.Translated from Poroshkovaya Metallurgiya, No. 2 (122), pp. 65–70, February, 1973.     

Thermionic emission properties of cermets of eutectic compositions in Me(IV)-(C,B)-(Mo,Re, W) systems

Conclusions Sintered eutectic (Ti, Zr, Hf)C-(Mo, Re, W) and ZrB₂-(Mo, Re, W) cathode cermets having a quasieutectic coarse-conglomerate structure are characterized by high stability of emission, and their effective work function is lower than that of their most emission-active components. The rapid stabilization of the emission characteristics of the eutectic cathode cermet composites is linked with the specific character of electron exchange between their phases, which creates optimum conditions for the formation of a self-stabilized structure on the surface of an emitter. The relative fall in work function exhibited by the cathode cermets investigated compared with their metallike compound components grows with increasing work function of their pure metallic components. Composite emitters of the eutectic compositions of the MeC (MeB₂)-Me' (where Me' = Mo, Re, W) systems are film-type emitters, on whose surfaces thin layers of the metal Me' form during heat treatment (sintering) and actual operation. The metal surface layers adsorb atoms from the metallike compounds MeC and MeB₂, which are supplied to the surfaces of the emitters by diffusion.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 81–87, January, 1980.     

Thermodynamics of Component Interactions in Liquid Alloys of the Ternary Systems Ge(Al,Si) ― Ga ― Gd

The concentration dependence of the integral enthalpy of mixing in liquid alloys of the ternary systems Ge(Al, Si) Ga Gd at 1760 K, determined by the method of isoperibolic calorimetry and calculated using the surrounded atom model, was analyzed. Good agreement between H values obtained by both methods is noted. It was established that the interaction of gadolinium with components of the adjoining binary systems, which are characterized by the presence of intermetallic compounds, have a defining effect on the thermodynamics of alloy formation in the ternary systems Ge(Al, Si) Ga Gd.     

Effect of electrolysis conditions on the formation,structure, and magnetic properties of a finely divided iron-cobalt alloy

Conclusions Changing the Fe²⁺Co²⁺ ratio in the electrolyte strongly affects the composition of the alloy but not its current efficiency; the current efficiency falls only at iron-to-cobalt ratios in excess of 11. At a high cobalt ion concentration in the electrolyte both the current efficiency and the cobalt content of the alloy cease to vary proportionally to the ion concentration. An x-ray diffraction investigation has established that increasing the cobalt ion concentration in the electrolyte decreases the size of iron-cobalt alloy blocks, which manifests itself in the ratio range Fe²⁺Co²⁺=0.6. When this ratio is exceeded, the -phase of the iron-cobalt alloy becomes amorphous, but on the whole the particles of the deposit retain a crystalline structure owing to the presence of an independent crystalline cobalt phase. At high cobalt ion concentrations in the electrolyte the particles forming by electrolysis constitute a pseudoalloy consisting of the -phase of the cobalt alloy and the and -modifications of metallic cobalt. Lowering the Fe²⁺ Co²⁺ ratio brings about a steady decrease in the crystal lattice constant. Magnetic measurements have revealed the existence of maximum values of coercive force and magnetic induction in a range of Fe²⁺ Co²⁺ ratios close to unity.Translated from Poroshkovaya Metallurgiya, No. 9 (225), pp. 1–5, September, 1981.     

The phase equilibria in W-Fe-Co-Ni system alloys. II. Isotherms of the solidus and the phase composition of alloys containing 10 and 20% (Fe + Co + Ni) at temperatures above 1200°C

Conclusions The isostructural intermediate -phases Fe₇W₅ and Co₇W₆ in the W—Fe—Co system form a continuous series of -solid solutions. In the 1640–1630°C range the L + (Fe₇W₆) peritectic equilibrium in this system changes to a similar L + (Co₇W₆) equilibrium, where is the tungsten-base boundary solution.In the W-Fe-Co-Ni polythermal tetrahedron in the 1470–1460°C range conversion of the L +(Fe₇W₆)+, peritectic equilibrium into the similar L + (Co₇W₆) + , where is the nickel-, -ironcobalt-base boundary solution, occurs.Upon completion of crystallization at 1400°C, the W-Fe-Co system alloys with 10–20% (Fe + Co) have a + phase composition, while the W-Fe-Co-Ni system alloys with 10–20% (Fe + Co + Ni) accordingly have + , + + or + . At temperatures below 1215°C in alloys rich in iron, FeW may be formed instead of -phase and therefore the alloys may have an + FeW, + + FeW, + + + FeW and + + FeW phase composition.Translated from Poroshkovaya Metallurgiya, No. 5(281), pp. 86–89, May, 1986.     

Error in the determination of the particle-size distribution of a powder with a laser analyzer

Conclusions Simple expressions have been obtained from known parameters of a flow-type chamber for estimating errors in laser analyzer measurements of the main numerical particle size distribution characteristics of powders obeying the logarithmic normal law. It is shown that, in spite of marked errors (Fig. 1) in size measurements on single particles whose trajectories are deflected from the laser beam center, it is possible to attain high accuracy in the measurement of numerical particle distribution characteristics by suitable choice of aero or hydrodynamic particle stream focusing [5] (Table 1: maximum error in the determination of the amount of the main fraction in a powder of particle size 3/2 _f = 1.9% at 2_j = 15 and _f = 4.3% at 2_j = 72 m). Without good particle stream focusing, measurements may be very inaccurate (Table 1: _f = 24% at 2_j = 120 m and _f = 55.5% at 2_j = 170 m). The accuracy of laser analyzer measurements grows with increasing curvature (coefficient n) of analyzer calibration characteristics and vice versa. The q/qt relationships obtained may find application in the assessment of errors in particle size analyses of powders with particle distributions differing from the logarithmic normal law.Translated from Poroshkovaya Metallurgiya, No. 12(288), pp. 15–20, December, 1986.     

Polythermal Ti-∑MoNi (9∶1) section of the ternary system Ti-Mo-Ni

Conclusions As a result of an investigation of the titanium corner of the system Ti-Mo-Ni, a partial phase diagram of the Ti + (0–55%) MoNi (91) section was constructed. The solubility of Mo and Ni in-Ti is 0.65% MoNi. Thea + phase field is bounded by MoNi contents of 0.65 and 17% at 600°C, 0.5 and 14% at 700°C, and 0.4 and 6% at 800°C. At MoNi contents of 55% and higher, there is a + Ti₂Ni field, the existence of which was confirmed by x-ray structural studies.Translated from Poroshkovaya Metallurgiya, No. 2 (110), pp. 33–37, February, 1972.     

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.     

Formation of detonation coatings applied on an iron base

Conclusions The results of x-ray diffraction analysis indicate a complex multiphase composition of the areas adjoining the zone of contact of the coating with the base related to occurrence of the and -structural transformations. Mutual mixing of the materials of the coating and base in the liquid phase leads to alloying and stabilization of the high temperature modification of iron (-Fe) and cobalt (-Co).The structural transformation ( -Fe) has a significant influence on the processes of formation of detonation coatings of powders of pure metals (Co-Ni) applied on iron and leads to a reduction in the level of mechanical properties of the joint.In the coating itself significant mixing of the sprayed metals occurs including different mechanisms of mass transfer such as mass transfer in the liquid and solid phases [1] with a depth of penetration of more than 10 m.On the boundary of the joint of the coating with the iron base relatively weak diffusion interaction of the contacting metals is observed. The width of this zone (5–10 m) is significantly less than that in spraying of a Co-Ni coating on an aluminum base [1].Translated from Poroshkovaya Metallurgiya, No. 10(298), pp. 60–65, October, 1987.     

Phase equilibria in the solidification range of alloys of the Ti-Ru-Ir system

Conclusions The processes taking place during solidification of the alloys of the Ti-Ru-Ir ternary system have been examined for the first time. The results show that the system contains three nonvariant quaternary equilibria with the liquid of the incongruent type: L + + at 2220°C, L + + at 1920°C, and L + + at 1465°C.In the region with the composition 0–50% Ti, the processes take place in the direction to the Ti-Ru side of the concentration triangle where they are also completed at the temperature of the binary eutectic L '+ equal to 1855°C. In the region with the composition 50–100% Ti the processes are completed at 1460°C at the nonvariant point corresponding to the eutectic reaction L + of the Ti-Ir binary system.Translated from Poroshkovaya Metallurgiya, No. 11(299), pp. 72–77, November, 1987.     

Creep of highly-porous iron compacts under conditions of cyclic α ↔ γ-transformations

Features of the creep of highly-porous iron compacts with cyclic -transformation are studied. Possible reasons are explored for acceleration of deformation during -transformation and sintering of compacts with -transformation.Kharkov University. Translated from Poroshkovaya Metallurgiya, Nos. 3–4, pp. 19–23, March–April, 1994.     

Diffusion processes in the sintering of nickel alloy powders with spherical particles under pressure

Conclusions Hot gasostatic pressing and subsequent annealing at 1200C result in the formation of 160–200-m diffusion zones between particles, which extend over practically the whole particle widths. During sintering under conditions of hot hydrostatic pressing, which is characterized by a shorter period of annealing at any given temperature and pressure, the widths of the diffusion zones after sintering and annealing attain 50–65m. The optimum diffusion zone width in the sintering of particles making good contact with one another (pure and even surfaces) is about 30–40m. However, the presence of oxides, carbide phases, and more complex compounds on the surfaces of particles substantially increases the optimum width of this zone. In such a case the optimum width is determined by the need for diffusion to cross interparticle contacts with diffusion-inhibiting barriers. In view of this, for particles of the nickel alloys investigated the optimum diffusion zone width may be taken to be 100m. At this width there are no areas in which the diffusion zone width is less than 40m, i.e., the minimum thickness at which strong bonds can be expected to form between particles.Translated from Poroshkovaya Metallurgiya, No. 5(233), pp. 38–41, May, 1982.     

Buckingham-potential parameters and relations between them for solids

Parameters m and n in the Buckingham potential in the form =[U₀mn/(m – n)]{(1/m)Y^–m – (1/n)exp[n(1–Y)]} have been calculated for 79 elements and 35 compounds, which have been compared with data on =c_v/(U₀) and =KV₀/c_v, in which U₀ is the cohesion energy, Y=(V/V₀)_1/3, V a volume with equilibrium value V₀, ... c_v the specific heat, the thermal-expansion coefficient, and K is the bulk elastic modulus. It is found that m is dependent essentially on and n on . These relationships have been approximated, and conclusions are drawn from them about the most reliable input data, particularly K because of the large spread in published values. A study is made on the relation of m and n to the positions of the elements in the periodic system and the electron structures.Institute of Problems of Materials Sciences, National Academy of Sciences of the Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, No. 5–6, pp. 118–126, May–June, 1994.     

Special features of the ductile-brittle transition in iron-based powder materials. II. Physicomechanical model of the ductile-brittle transition in cracking resistance tests

Conclusions The presence of pores in the material leads to the redistribution of stresses in the material and to localization of strains in small volumes between the pores. The susceptibility to ductile failure increases with increasing porosity.At –196°C, the failure mechanism of the porous materials based on iron changes from ductile to brittle (cleavage) with decreasing porosity. The dependence of cracking resistance on the porosity of these materials is nonmonotonic and the maximum cracking resistance is recorded at porosity values at which the failure mechanism changes. The nonmonotonic nature of cracking resistance reflects the high sensitivity of this characteristic to the change of the stress state in the material. The change of the stress state in the ductile-brittle transition temperature range can be described by the condition _f = _T. In the porous materials examined this condition is valid because of the specific form of the _f- and _T- dependences. The model of the ductile-brittle transition proposed in this work can be used to determine the analogy between the cold brittleness temperature T_br and the critical value of porosity _c corresponding to the point of intersection of the _f- and _T- curves for the porous materials.Translated from Poroshkovaya Metallurgiya, No. 3(303), pp. 39–42, March, 1988.     

Phase relations in the Ti-TiNi-NbNi-Nb region of the ternary system Ti-Nb-Ni

We have used microstructural, differential thermal, x-ray phase, and electron probe analysis to study alloys in the Ti-TiNi-NbNi-Nb region of the ternary Ti-Nb-Ni system, both as-cast and annealed at 900°C. We have located a pseudobinary TiNi- section, where is a Nb-rich (Nb, Ti)-based solidsolution. The pseudobinary eutectic point parameters are 1170°C and 38 Ni 26 Nb (at. %). We have found two invariant peritectic four-phase equilibria for crystallization of the alloys in the region of interest: L + TiNi + Ti₂Ni (950 °C) and L + TiNi + NbNi (1140°C). We have not confirmed the existence of a ternary compound Ti₃(Ni,Nb)₂.Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3/4, pp. 48–54, March–April, 1995.     

“Activity” of powders in the sintering of single-component compacts

Summary A study has been made of the shrinkage characteristics of compacts obtained by pressing: 1) active powders of electrolytic origin, 2) powders thoroughly deactivated by high-temperature annealing, and 3) a mixture of equal amounts of the above two powders. It is shown that the observed shrinkage characteristics can be qualitatively explained by assuming that, in addition to the usual mechanism of deactivation operating during annealing, there is also a mechanism of activity loss resulting from defect migration from active to deactivated particles.Translated from Poroshkovaya Metallurgiya, No. 4 (64), pp. 18–21, April, 1968.     

Densification of metal powders during heating under high pressures of up to 80 kbar

Conclusions An experimental study was made of the densification of metal powders during heating under pressures of up to 80 kbar. The character and kinetics of densification of powders during heating were found to differ markedly depending on whether the pressure applied to them was higher or lower than the critical pressure. It is demonstrated that the minimum necessary condition for attaining the density of the nonporous metal in the densification of a powder under the critical and higher pressures is the development of thermally activated dislocation motion processes in the range (0.3–0.4)T_m. The densification of powders at pressures below the critical is controlled by particle flow processes, its kinetics being strongly dependent on the applied pressure and temperature.Translated from Poroshkovaya Metallurgiya, No. 11(191), pp. 28–33, November, 1978.     

Enthalpy of Mixing and Excess Volume of Binary Metallic Melts of Eutectic Systems

The enthalpies of mixing H and excess volumes V were analyzed in alloy formation from binary metallic eutectic systems. Three types of systems can be distinguished: I with H > 0, V > 0; II with H > 0, V 0; III with H < 0, V 0. The hypothesis is discussed that another yet unstudied group IV exists in which H < 0, V < 0.     

Layered Powder Metallurgy Wear- and Corrosion-Resistant Materials for Tool and Tribological Applications. Structure and Properties

Three-layered non-tungsten hard alloys for tool applications of the type KKhNFT5 KKhNFT25 KKhNFT5 and layered powder metallurgy materials for tribological applications with a working layer of composites based on stainless steels were investigated. Basic requirements for the creation of wear- and corrosion-resistant powder metallurgy materials for tool and tribological applications were formulated. These mainly concern their composition and structure.     

Sintering kinetics of tantalum carbide

Conclusions Tantalum carbide sinters at a temperature above 2500C. Decreasing the powder particle size activates the sintering process, but even with a powder of 0.17-m particle size specimens sintered at 2700C have a porosity of 11%. Coarse powders (> 7–8 m) sinter, without densification, at 2000–2200C by a surface self-diffusion mechanism. Fine powders (<7–8 m) undergo densification already at temperatures above 1400C by a diffusion-viscous flow and a volume self-diffusion mechanism during long holding periods and also probably by an activated grain-boundary sliding mechanism in the initial stage of sintering after rapid heating.Translated from Poroshkovaya Metallurgiya, No. 10(238), pp. 16–19, October, 1982.