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.     

Strength characteristics of matrials produced by hot forming of porous powder compacts. I. The influence of porosity,carbon content,and the method of compacting on the tensile,shear, and compressive yield strengths

Conclusions The mechanical characteristics (_t, ) of powder metallurgy steels depend upon the porosity as a weakening factor and work hardening as a strengthening one. The tensile strength is more sensitive to porosity and less susceptible to work hardening than the shear strength. The compressive yield strength depends practically only upon work hardening and the size of the metal cross section.In comparison with hot rolled of the same composition, powder metallurgy low-porosity steels possess higher characteristics _t, , and _0.2 ^comp , which may be explained by the strengthening action of work hardening.Powder metallurgy steels produced by extrusion have higher values of _t than hot formed as the result of improvement in the quality of the intergranular contacts and orientation of the nonmetallic inclusions while there is practically no difference in the characteristics and _0.2 ^comp of these materials.Translated from Poroshkovaya Metallurgiya, No. 3(279), pp. 88–91, March, 1986.     

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.     

Effect of porosity on microplastic deformation of iron base powder materials

Conclusions By the method of subjecting beams of uniform strength to bending tests we measured the modulus of elasticity of sintered iron base materials in a broad interval of porosity (0–40%).With porosity from 10 to 25% the curves of microyield are reduced to a single curve of strain-hardening of compact material by normalization to the coefficients K = E_o/E_gq.Deviations from similarity are found in the region of small (<10%) and high (>25%) porosity. The authors bring these effects into connection with the change of the structural state of the material.In the region of microplasticity (_pl = 10^–6-10^–3) a characteristic feature of iron base sintered materials with porosity of less than 25% is parabolic strengthening: ^1/2. An analysis of the curves of microyield in coordinates -^1/2 revealed that strengthening proceeds in stages.For materials with porosity of more than 25% the yield stress and strain are correlated by a dependence of the type ln .Translated from Poroshkovaya Metallurgiya, No. 7(319), pp. 79–84, July, 1989.     

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.     

The Cr ― Ta ― C Melting Diagram in the (Cr) ― (Ta) ― (TaC) Region

It has been found from an experimental study on alloys in the Cr Ta C system in the region of the (Cr) (Ta) (TaC) subsystem at melting (crystallization) temperatures that there are two nonvariant four-phase equilibria of congruent type: L_E (Ta) + (Ta₂C) + (TaCr₂) at 1935°C and L_E (TaC) + (Cr) + (TaCr₂) at 1675°C; there is also one four-phase nonvariant equilibrium of incongruent transition type: L_U + (Ta₂C) (TaC) + (TaCr₂) at 1943°C, and two nonvariant three-phase equilibria of congruent type: L_e (Ta₂C) + (TaCr₂) at 1960°C and L_e (TaC) + (Cr) at 1695°C. The phase diagram for the subsystem has been constructed in the form of projections of the solidus and liquidus surfaces, and a melting diagram has been constructed.     

Mechanical properties and microstructure of sintered titanium alloys

Conclusions A study was made of the mechanical properties and microstructure of titanium alloys in the sintered state. The influence of alloying elements was evolved. It was established that for alloys used in the sintered state it is favorable to use vanadium, aluminum, and molybdenum as alloying elements.The titanium alloy containing 3% Al and 3% V, made by the method of combined reduction of oxides of TiO₂, Al₂O₃, V₂O₅ by calcium hydride (_B-774.2 MN/m², -15%, -26%, a_k-25.4 joules/cm²) and also the alloy Ti+3% Al+3% V+2% Mo (_B-857.5 MN/m², -14.3%,-27%, a_k-24.5 joules/cm²) can be recommended for the manufacture of components by methods of powder metallurgy.     

Deformation structure ofα-SiC single crystals

Conclusions The deformation of-SiC single crystals in bending with the direction of extension and compression approximately parallel to the basal face (the axis of bending parallel to (0001), T = 2000–2100°C) involves slip over the basal plane; the directions of slip are <11¯20> and <10¯10>. Accordingly, crystallographic planes rotate about parallel axes, <10¯10> and <11¯20>. Slip in the <10¯10> direction may be a consequence of migration of dislocations with Burgers vectors equal to b=2/3 <10¯10> (a full dislocation and <10¯10> (a partial dislocation). X-ray microdiffraction observations show [12] that partial dislocations with Burgers vector components parallel to [101¯1] frequently form in-SiC; travel of partial dislocations apparently plays an important part in the deformation of -SiC. The deformation of-SiC is accompanied by kink band formation [1].During the deformation process, dislocations pile up in slip planes, and their density increases by two to three orders; their distribution is very uneven, typical values of being 10⁸–10¹⁰ cm^–2 and values of _max of 10¹¹cm^–2 being recorded in zones with a large local curvature.Because of the changing specimen structure, two stages may be detected in the deformation process: 1) formation of elastically bent regions and 2) comminution (formation of microcracks within the specimen).The crystals investigated exhibited only micropolygonization, when the block size in the basal plane was 30 and the block disorientation 10. Neither postdeformation annealing for 10–30 h at 2000–2100°C nor prolonged (4–8 h) holding of specimens under load produced any macroscopic polygonization. The structure of naturally deformed specimens, too, was found to contain no polygonization macroblocks. It would appear that, because of the appreciable activation energy for diffusion and strong covalent linkage in-SiC, dislocations cannot readily climb over large (>10) distances in this compound; in this connection, the relaxation properties of-SiC would be expected to be weak.The methods of investigation employed in our work are comparatively simple to use. They do not give any information about elementary deformation acts, but throw a light on the character of lattice variation in various volumes (V ranging from 0.1t to 6.0t mm³, where t=200–500 is the crystal thickness) and are particularly useful in topographic x-ray photography when there is no contrast on individual linear defects in crystals.Translated from Poroshkovaya Metallurgiya, No. 8 (128), pp. 63–72, August, 1973.     

Reaction of Composite Ceramic Materials with Corrosionally Active Media

The oxidation of composite powders and monolithic AlN SiC, AlN SiC TiB₂, and AlN SiC ZrB₂ ceramics in air up to 1600°C was studied by the methods of thermogravimetric, differential thermal, x-ray diffraction, and electron-probe microanalysis. The exceptionally high corrosion resistance of these materials was established. The corrosion resistance and possibility of using structural ceramics of the systems TiB₂ AlN, TiB₂ TiN, and TiC_0.5N_0.5 in sea water was demonstrated. The toxicity of Si₃N₄, AlN, BN, and TiN powders was analyzed on the basis of their reactions with biochemical media. It was proven that TiN based materials are highly stable in the oral cavity.     

The Solidus Surface in the Ti ― Ni ― Hf System in the Ti ― TiNi ― HfNi ― Hf Region

Studies have been done on the phase equilibria at subsolidus temperatures in the Ti TiNi HfNi Hf region of the Ti Ni Hf ternary system. The phases based on binary compounds and solid solutions of these components are accompanied in the equilibria by a phase based on an equiatomic ternary compound. This new phase belongs to the family of Laves phases and has a hexagonal crystal structure of MgZn₂ type. The solidus surface in the Ti TiNi HfNi Hf subsystem consists of the surface of the ternary phase alone, the surfaces of the six solid solutions based on the components and binary intermediate phases, the planes of five conode triangles, and the corresponding lineated surfaces.     

The phases in the lanthanum-germanium system

Conclusions The lanthanum-germanium system was investigated. The existence of four, previously established compounds was confirmed. The width of the homogeneity region of the lanthanum-rich compounds is narrow. The width of the homogeneity region of lanthanum digermanide extends over the composition range LaGe-LaGe_2.0, which corresponds to germanium contents of 42–51%. Lanthanum digermanide exhibits two modifications with crystalline structures of the -ThSi₂ and -GdSi₂ types, which are capable of independent existence at room temperature. The phase with an -GdSi₂ type structure forms at germanium contents corresponding to the compositions LaGe_1.8-LaGe_2.0, while the -ThSi₂ type structure forms at germanium contents lower than theoretical (42–45 wt.%). At the composition LaGe_1.7, the phases with the -GdSi₂ and -ThSi₂ type structures coexist.Translated from Poroshkovaya Metallurgiya, No. 12 (72), pp. 42–44, December, 1968.     

Mechanical treatment of powders of refractory carbides

Conclusions The model of mechanical treatment constructed in this work makes it possible to reduce all the parameters of this treatment to three generalized parameters: the mean energies of movement of the spheres_s, particles _p, and the fraction of absorbed energy . The main input parameters of the conditions are the vibrational speed V_a = A and the flow of the powder qv.On the basis of calculations of the energy characteristics of mechanical treatment of the powders of the tantalum carbides and semicarbides we can estimate the contribution of mechanical energy of this treatment to the activation of the processes of synthesis of the semiand subcarbides of these metals. Specifically, the effect of synthesis of the refractory tantalum semicarbide directly in the chamber of the vibratory mill during mechanical treatment can be explained.Translated from Poroshkovaya Metallurgiya, No. 4(280), pp. 91–96, April, 1986.     

Wear- and Scaling-Resistant Coatings Based on TiCN

The composition, structure, and properties of coatings obtained by the high-velocity gas-flame spraying of composite powders based on TiCN with additions of SiC, AlN, SiC AlN/Al₂O₃ and a binder of NiCr based alloy were investigated. The working surfaces of coatings were studied by metallographic, petrographic, x-ray diffraction, electron-probe analyses, and scanning electron microscopy. It was determined that coatings 200 m in thickness had a typical finely dispersed lamellar structure with layers enriched in titanium alternating with layers of NiCr alloy. The tribological properties of developed coatings were superior to those of the standard WC + 8% Co alloy: under dry friction at a load of 2 MPa and sliding velocities in the range 5-15 m/sec the coefficient of friction was 0.17-0.11, and wear rate 3.4-8.5 m/km. The high oxidation resistance of the coatings is due to the presence, in the outer scale layer, of refractory compounds Al₂SiO₅, (Cr, Al)₂O₃, and Al₂TiO₅, which prevent the diffusion of oxygen into the substrate. The mass gain of the coating based on TiCN SiC AlN was 1.42 mg/cm₂ at 1450°C.     

Strength characteristics of the materials obtained by hot forging of porous powder preforms. II. Effect of heat treatment on the tensile and shear strength and the compressive yield stress

Conclusions Annealing of the powder metallurgy steels leads to a reduction in the values of the parameters _t, , and ^c _0.2. During this process, they become lower than those of the hot rolled (worked) products. However, after annealing, the stability of all the three characteristics increases. Quenching followed by a low-temperature tempering improves the parameters _t, , and ^c _0.2, but in this case, brittleness of the material increases. With increasing tempering temperature, all the three parameters decrease and at 600°C, they are virtually at the same level as that obtained after annealing at this temperature.The change in the yield stress after quenching and tempering or after annealing determines to a significant extent the nature (whether brittle or ductile) of shear fracture.Translated from Poroshkovaya Metallurgiya, No. 4(280), pp. 73–75, April, 1986.     

Interaction of Cerium Oxide with Hafnium,Zirconium, and Yttrium Oxides at 1500°C

Using the methods of x-ray diffraction and petrographic analysis as well as electron microscopy, phase relationships in the ternary systems ZrO₂ Y₂O₃ CeO₂ and HfO₂ Y₂O₃ CeO₂ were investigated over the entire range of concentrations at 1500°C. The accuracy of the phase relationships of the binary systems HfO₂ CeO₂, ZrO₂ CeO₂, and CeO₂ Y₂O₃ at this temperature was improved. Isothermal sections of the ternary phase diagrams at 1500°C were constructed. Specimens of various compositions were prepared from nitrate solutions by evaporating, drying, and heat treating at 1500°C. These systems are characterized by the formation of broad ranges of solid solutions based on C-Y₂O₃, F-CeO₂, F-HfO₂ and ZrO₂, and narrow ranges based on T-ZrO₂ and M-HfO₂. No new phases were detected. The course of isoparametric lines in the solid solution ranges of F-HfO₂ (ZrO₂) leads to the assumption that yttrium and cerium ions substitute for each other, but no appreciable substitution by them for zirconium or hafnium ions occurs.     

Ways of improving the quality of 80% Ni-20% Cr alloy coatings

Conclusions It has been established that recrystallization annealing increases at of an 80/20 alloy/ substrate composite and decreases its _s and, consequently, such heat treatment may be beneficial to parts provided with skins but not to coating/substrate composites. A study was made of the structural changes induced by the reaction of SiC powder with the substrate material investigated during recrystallization annealing. It is shown that the strength of adhesion _ad of an 80/20 alloy coating to its substrate can be increased by blasting the latter with a coarse SiC fraction (800–1000 µm).Translated from Poroshkovaya Metallurgiya, No. 9(201), pp. 84–89, September, 1979.     

Static and cyclic strength of a uniaxially reinforced material in bending (part 1)

Conclusions A built-up degree of damage =f/f_o 8% has virtually no effect on the static strength of an AD33-B CM operating in air. The arbitrary fatigue limit corresponding to this volume of damage on a basis of 2–10⁵ cycles may be taken to be equal to (0.5–0.55) _t. Accelerated buildup of damage on a basis of 2–10⁵ cycles is observed at _a > (0.5–0.55) _t.Translated from Poroshkovaya Metallurgiya, No. 7 (259), pp. 65–67, July, 1984.     

Structural Features and Properties of Alloy 84% WC ― 16% Co,Obtained by Hot Pressing in the Solid and Liquid Phases. Part 2. Influence of the Temperature at which the Specimens are Made on Their Physicomechanical Properties

We have studied the changes that occur in the resistivity, the transverse bending strength, and the fracture toughness (cracking resistance) of a hard alloy obtained by hot pressing at about 500 MPa and sintering over a wide range of temperatures (950-1450°C) as well as the how those parameters are affected by solid-phase and liquid-phase annealing. The porosity dependence of the resistivity is shown not to be single-valued. Other factors affect the resistivity, e.g., the degree of particle interaction and the state of the structural components, which vary with the porosity. The resistivity curve for hot-pressed specimens has an inflection in the region of 1200°C. The resistivity increases at a faster rate at lower temperatures. In the temperature range studied the porosity dependence of the transverse bending strength and the fracture toughness is linear: _b = ⁰ _b(1 – 3.53) and K _1c = K ⁰ _1c (1 – 3.44). Prolonged solid-phase annealing of hot-pressed specimens improves their mechanical properties owing to a decrease in porosity.     

Deformation coefficients of metal powders

Conclusions The total deformation coefficients of metal powders are determined by the ratios of the final dimensions of a porous part being deformed to the corresponding dimensions of a nonporous body of the same mass. Comparable total deformation coefficients of metal powders have been represented as the products of the partial deformation coefficients characterizing the possible deformation of a nonporous body of the same mass upon its transition into the free-flowing state and the deformation taking place during the transition from the free-flowing into the porous state under the action of pressure. The deformation coefficients of metal powders are uniquely determined by the relative densities before and after the application of pressure for all the linear principal strain schemes, for the plane schemes , when _10p = _20p ^–1 , , when _10p = _30p ^–1 , and , when _20p= _30pand the volume schemes of isostatic compression and extension when _10p ^–1 = _30p. In the determination of the deformation coefficients for the remaining principal strain schemes, it is necessary to take into account the final dimensions of the porous part being deformed.Translated from Poroshkovaya Metallurgiya, No. 11 (119), pp. 18–23, November, 1972.     

Phase Formation and Structure of Bronze ― Iron ― Graphite Composite Powder Material during Hot Forming

Copper tin iron graphite material prepared by hot forming is studied. It is established that on heating billets to 850°C Cu Sn alloy forms and there is no copper or tin in pure form after heating. The Fe Sn phase does not even form locally. Bronze grains have a banded relief that is connected with formation of a large number of twins and additional dislocations in Cu(Sn) solid solution. This structural inhomogeneity facilitates material strengthening and high operating properties.