Phase equilibria in titanium-rich alloys of the Ti — Fe — Nb — Al system

Isothermal cross sections at temperatures of 750°C and 550°C of the phase diagram of the quaternary system Ti — Fe — Nb — Al in the region of titanium-rich alloys for a constant aluminum content of 5 mass % were plotted using metallography, x-ray diffraction, and local x-ray spectral analysis. In the temperature range 550–750°C in alloys with 5 mass % aluminum, the maximum solubility of iron in α-titanium reaches ∼2 mass % for a niobium content of 3 ± 0.5 mass %. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(412), pp. 27–32, March–April, 2000.     

Phase equilibria in vanadium-rich alloys of the V-Ni-Al system

Vanadium-rich alloys of the V-Ni-Al system were studied by the methods of metallographic, x-ray diffraction, and electron beam microprobe analysis. The boundaries of the phases, and the vertices of the conoidal triangle αβσ, in the vanadium corne, of the 1200°C isothermal section were determined. The maximum solubility of aluminum in the σ-phase is 6 at. %. The homogeneity range of the NiAl-based β-phase is very broad; the maximum solubility of vanadium in β reaches 41.5 at. %. The maximum solubility of nickel in the vanadium solid solution is 25 at. %. Alloys containing 15–20 % Al and 20–30% Ni exhibit a tendency to dispersion haraen and, therefore, might serve as a basis for the development of a new generation of radiation-resistant materials. Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 43–47, July–August, 1997.     

Reaction synthesis of Ni-Al-based particle composite coatings

Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 vol pct aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 °C to 1000 °C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500 °C to 600 °C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600 °C to 1000 °C), diffusional reaction between NiAl and nickel produces (γ′)Ni₃Al. The final equilibrium microstructure consists of blocks of (γ′)Ni₃Al in a γ(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation, and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.     

Magnetizing roasting of leucoxene concentrate

The phase transformations occurring during magnetizing roasting of leucoxene concentrate in the temperature range 600–1300°C are studied. It is demonstrated, that in the temperature range 600–800°C, only iron oxides are reduced to a metallic state; at temperatures above 800°C, combined reduction of iron and titanium oxides takes place. At 1050°C, reduced specimens are represented by the Ti₅O₉ and Ti₆O₁₃ Magnéli phases. The formation of iron metatitanate (FeTiO₃), under reduction conditions and the existence of ferrous iron ions in the Magnéli phases slightly degrade the magnetic properties of the products of magnetizing roasting. In high temperature region (1200–1300°C), a similar effect is exerted by the formation of iron dititanate or anosovite in the system. The possibilities of eliminating the undesired factors decreasing the magnetic properties of the products of magnetizing roasting are determined.     

TiNi-YNi alloys. Interaction with hydrogen

Phase equilibria in the Ti-Ni-Y system at the TiNi-YNi section are studied using physical and chemical methods (metallography, radiography, differential thermal and electron microprobe analyses). Data on hydrogen sorption and desorption by ternary system Y-Ni alloys are obtained. It is shown that the TiNi-YNi section is quasibinary eutectic with the coordinates 990 °C and ∼40 at.% Y. The solubility of Y and Ti in TiNi and YNi mononickelides is approximately <0.3 and 1 at.%. Equiatomic ternary (TiNiY) phase in the Ti-Ni-Y is not found. The alloy of equiatomic composition turns out to be ternary: <Ti₂Ni> + <Y3Ni> + <Y₂Ni₃>. Based on sorption data, two hydrides may exist in the alloys with 30 to 40 at.% Y, which are thermally stable at 800 °C and over a range of 300 to 600 °C. It is revealed that the maximum amount of hydrogen at 0.1 MPa is absorbed by binary the YNi, YNi₂, and YNi₅ phases at room temperature. Traslated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 83–95, 2007.     

Alloy behavior and the phase equilibrium diagram for the Sc-Ru-Rh system. Part 2. melting diagram for the Ru-ScRu-ScRh-Rh Partial system

Microstructure, x-ray phase, and microprobe analyses have been together with temperatures for the start of melting determined by the Pirani—Alterthum method in deriving the projection of the liquidus surface and crystallization scheme for the Ru—ScRu—ScRu—Rh partial system. The liquids surface is made up of five surfaces for the primary crystallization of solid solutions based on ruthenium and rhodium, phases based on the compounds ScRu₂, ScRh₃, and the δ phase (a continuous solid-solution series between isostructural phases of CsCl type based on ScRu and ScRh). There are the three nonvariant four-phase equilibria involving the liquid: L+(Rh)⇀(Ru)+(ScRh)₃ (1640°C) and L⇀δ+(ScRh₃)+(ru) (1520°C), which involve separate monovariant processes. Materials Science Institute. Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 31–35, January–February, 1997.     

On the decomposition of solid solutions of magnesium in aluminum

A nonequilibrium version of measuring the electromotive force during a continuous decrease in the temperature at a rate of 5–7 °C/min is used to study the thermodynamic properties of solid solutions of magnesium in aluminum. The studies show that the abrupt change in the potential of an alloy containing 20–30 mol % Mg at 370–380°C reliably correlates with the decomposition of the solid solution formed at 450°C.     

The niobium (columbium)-palladium constitution diagram

The Nb-Pd system was investigated over the entire composition range by metallography and X-ray diffraction analysis. The solubility limits of terminal and intermediate phases and solidus temperatures were determined. α-Nb dissolves ∼36 at. pct Pd at. 1520°C and ∼20 at. pct Pd at 800°C; α-Pd dissolves ∼31 at. pct Nb at 1610°C and ∼18 at. pct Nb at temperatures below 1500°C. The presence of three intermediate phases NbPd₂ (MoPt₂-type), α-NbPd₃ (TiAl₃-type), and β-NbPd₃ (β-NbPd₃-type) was confirmed; NbPd₂ melts at 1610°C and one of the NbPd₃ phases transforms at the same temperature into α-Pd solid solution which melts at 1625°C. In addition, an approximately equiatomic high-temperature phase α-NbPd with a homogeneity range of ∼11 at. pct was found which melts at 1520 to 1565°C and probably is an extension of and isomorphous with the α-Pd solid solution. Five three-phase reactions are described, and crystal chemical relationships are discussed. D. P. PARKER formerly with MIT . R. C. MANUSZEWSKI formerly with the ADAHF Research Unit at NBS.     

The development of technology for making SvAK12 welding wire from shaving billet

A technology for making a welding wire with a diameter of 1.2 and 2.0 mm from the shavings of SvAK12 aluminum alloy is developed. This technology includes hot briquetting the graded shaving scrap at 400–420°C, the hot extrusion of briquettes at 460–470°C with elongation factors of 32 and 56, cold wire drawing the extruded bars with average unit reductions for a pass of 15–20%, and intermediate annealings at 400°C. It is shown that this wire is suitable for soldering parts of aluminum alloys, and the level of the mechanical properties allows it to be recommended for wide application.     

Effect of process parameters in the decomposition of a cryochemical salt product of the Bi - Pb - Sr - Ca - Cu - O system on the structure and properties of a ceramics

A study was made of the effect of the temperature and time of decomposition of a salt product on the phase composition, microstructure, and magnetic susceptibility of a Bi - Pb - Sr -Ca - Cu - O superconducting ceramics. Holding the powder at 570°C slows the formation of the high-temperature phases, while increasing the decomposition temperature to 840°C and increasing the time of decomposition at 815°C have the same effect on the concentrations of the phases Ca₂PbO₄, CuO, and (CaSr)₂CuO₃. The data obtained on magnetic susceptibility, together with the results of microscopic and x-ray spectral studies, made it possible to evaluate the effect of the morphology of the grains and the grain boundaries on the superconductivity of the sintered specimens. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 91–100, May–June, 2000.     

The tantalum-palladium constitution diagram

The Ta-Pd system was investigated over the entire composition range by metallography, X-ray diffraction and electron microprobe analysis. The solubility limits of terminal and intermediate phases and solidus temperatures were determined. α-Ta dissolved ∼20 at. pct Pd at 2550°C and ∼10 at. pct Pd at 1000°C; α-Pd dissolves ∼22 at. pct Ta at 1730°C and ∼18 at. pct Ta at 1000°C. The presence of four intermediate phases a, (β-U type), α-TaPd (TiCu type), TaPd₂ (MoPt₂ type), and TaPd₃ (TiAl₃ type) was confirmed; they melt or decompose (α-TaPd) at about 2550, 1410; 1800, and 1770°C, respectively. In addition, an equiatomic high temperature phase, β-TaPd was found which melts at ∼1720°C and may be an extension of and isomorphous with the α-Pd solution. Seven three-phase reactions are described. Formerly with Massachusetts Institute of Technology     

Titanium-boride eutectic materials. Structure of the Ti-Nb-B alloys and phase equilibria

The structure of Ti-Nb-B alloys that are cast and annealed at subsolidus temperatures and at 1400°C is experimentally analyzed (x-ray diffraction, metallography, and electron probe microanalysis), and so are temperatures of their phase transformations (differential thermal analysis and pyrometry). No ternary phases are found in the alloys. Projections of solidus and liquidus surfaces, an isothermal section at 1400°C, and a vertical section at 7.5 at.% B are constructed. A reaction scheme is proposed for alloy crystallization. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 1–2(453), pp. 72–87, 2007.     

Influence of Aluminum Additives on the Content and Parameters of the Fine Structure of Titanium Silicon Carbide in SHS Powders

The dependence of the phase composition and parameters of a fine structure of titanium silicon carbide in powders formed by the self-propagating high-temperature synthesis on the aluminum concentration in the 5Ti/2Si/1C reaction mixture is investigated. The aluminum content is varied in a range of 0.1–0.4 mole fraction with the conservation of the total carbon content. It is established that the additives of aluminum not only affect the yield of titanium silicon carbide, but also promote the preferential formation of Ti5Si3 in synthesis products instead of TiSi2 identified in powders containing no aluminum. The introduction of a small amount of aluminum (0.1 mole fraction) leads to the formation of the Ti3Si1 – xAlxC2 solid solution and makes it possible to decrease the content of impurity phases in SHS powders by 6%. The silicon carbide concentration in SHS powders decrease at a higher aluminum content in the reaction mixture, while that of binary compounds (TiC, Ti5Si3, TiAl) correspondingly increases. No noticeable effect from the introduction of aluminum on the parameters of the crystal lattice of titanium silicon carbide in SHS powders is found in concentration limits of 0.1–0.25 mol %. A noticeable increase in parameters of a and c for Ti3Si1 – xAlxC2 (from a = 3.067 Å, c = 17.67 Å to a = 3.07 Å, c = 17.73 Å) with the conservation of the c/a ratio in limits of known values (c/a = 5.78) is observed only with the aluminum concentration of 0.4 mole fraction. The crystallite size of titanium silicon carbide depends, first and foremost, on the combustion parameters. At the same time, the deformation of the crystal lattice of Ti3Si1 – xAlxC2 in SHS powders increases monotonically with an increase in the aluminum content in the reaction mixture in the concentration range under study.     

Phase equilibria in the Lu-Pd system in the composition range 0–50 at % Lu

X-ray diffraction, differential thermal analysis, and electron microscopy are used to study the crystal structures and formation sequence of intermetallics in the Lu-Pd system in a composition range of Pd-(0–50 at %) Lu. The alloys are synthesized using high-purity lutetium. Within the composition range under study, the system is characterized by terminal Pd-based solid solutions with a lutetium content up to 10 at % Lu (at 1000°C) and a number of intermetallics (Lu₃Pd₄, Lu₂Pd₃, LuPd, LuPd₃, Lu₁₀Pd₂₁). A nonequilibrium bertholide phase is found to form in the composition range from 30 to 45 at % Lu. The phase diagram is given in the composition range Pd-(0–50 at %) Lu.     

Structure and high-temperature strength of composite materials based on boron nitride

The structure and physicomechanical properties of composite materials based on boron nitride within which new phases (mullite and sialon) form during hot compaction are studied. It is established that the microstructure of composites is specified by their texture formation caused by the crystal morphology of boron nitride particles and it is almost independent of composite phase composition. It is shown that the main factor that affects strength is porosity. The dependence of strength on porosity is exponential in character. The strength of boron nitride-mullite and boron nitride-sialon composites is 110–140 MPa and at 20–1200°C it is almost unchanged. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(449), pp. 33–39, May–June, 2006.     

The vanadium-platinum constitution diagram

The system V-Pt was investigated over the entire composition range by metallography, X-ray diffraction and electron microprobe studies. There are at least four equilibrium intermediate phases in this system and they are stable to progressively higher temperatures with increasing vanadium concentration. The phases which have been observed are: γ^′, cubic, Cu₃Au type; θ, tetragonal, TiAl₃ type; δ, orthorhombic, MoPt₂ type; ζ, orthorhombic, AuCd type; and β, cubic, Cr₃Si type (A15). The gg^′ phase is possibly metastable. A very stable ribbon-like growth of ζ phase in the fcc platinum terminal solid solution has been observed in alloys containing about 43 at. pct V. The platinum terminal solid solution forms a congruent melting maximum at about 1805°C. A eutectic reaction occurs at 1720° ± 10°C and a peritectic reaction is indicated at 1800° ± 10°C. Vanadium is soluble in the fcc platinum terminal solid solution up to about 57 at. pct at 1720°C. Platinum dissolves only to the extent of about 12 at. pct at 1800°C in bcc α-V.     

Mechanical Properties and Microstructural Evolution of Friction-Stir-Welded Thin Sheet Aluminum Alloys

Friction stir welding of thin aluminum sheets represents a potential goal for aircraft and automotive industries because of the advantages of using this new technological process. In the current work, the microstructural evolution and mechanical behavior of 6082T6-6082T6, 2024T3-2024T3, and 6082T6-2024T3 thin friction-stir-welded joints were investigated. Uniaxial tensile testing at room temperature, 443 K, 473 K, and 503 K (170 °C, 200 °C, and 230 °C) was used to determine the extent to which these ultra-thin joints can be used and deformed. The tensile stress–strain curves showed a decrease of the flow stress with increasing temperature and decreasing strain rate. The ductility of 6082T6-6082T6 joints generally improved when deformed at warm temperatures. It was almost constant for the 6082T6-2024T3 and reached the higher value in the 2024T3-2024T3 when deformed at 443 K and 473 K (170 °C and 200 °C) when compared with the room temperature value. Tensile specimens fractured in the middle of the weld zone in a ductile mode. The precipitation and growth of S’ type phases strengthens 2024T3-2024T3 joints during deformation. In the 6082T6-6082T6, β″ precipitates show some increase in size but give a lower contribution to strength. At 503 K (230 °C), recovery mechanisms (dislocation reorganization inside the deformed grains) are initiated but the temperature was not enough high to produce a homogeneous subgrain structure.     

Phase equilibria in the Cr-Ni-C system and their use for developing physicochemical principles for design of hard alloys based on chromium carbide

The Cr—Ni—C phase diagram at the melting point was plotted by a combination of procedures (metallography, x-ray, microprobe, differential thermal analysis, Pirani—Alterthum method, etc.). A general feature of this system is the existence of equilibria between the nickel-based phase and all the other phases. The temperature of the quasibinary (Ni)+(Cr₇C₃) eutectic was determined to be 1324±6°C. Based on both the phase diagram of the Cr—Ni—C system and the bending strength and Rockwell hardness of the alloys, the optimal composition of the initial carbide ingredient for production of hard alloys based on Cr₃C₂ with nickel—phosphorus binder was estimated as 13.0–13.3 at.%, substoichiometric with respect to Cr₃C₂. Institute of Problems in Materials Science, National Academy of Sciences of Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya. No. 5/6(395), pp. 13–24, May–June, 1997.     

Solid-phase prereduction of iron-vanadium concentrates and liquid-phase separation of the products of their reduction

The transformations that occur in ore grains during solid-phase carbon reduction of the metals from the iron-vanadium concentrates formed upon the beneficiation of the titanomagnetite ores from Southern Ural deposits are studied. Upon heating to 1000°C, the solid solution in titanomagnetite grains decomposes with the formation of magnetite and ilmenite; the reduction of iron begins in the temperature range 1080–1110°C, and the reduction of titanium begins at above 1215°C. The reaction mixture should be held at 1250°C for 45 min to ensure almost complete iron reduction and the minimum degree of titanium reduction. For rapid separation melting, this procedure results in vanadium-containing cast iron (0.43–0.5% V) with <0.15% Ti and a slag with 42–43% titanium oxides.     

The Al-Cu-Fe phase diagram: 0 to 25 At. pct Fe and 50

Isothermal sections of the Al-Cu-Fe equilibrium phase diagram at temperatures from 680 °C to 800 °C were determined in the region with 50 to 75 at. pct Al and 0 to 25 at. pct Fe using scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques. This re- gion includes the face-centered icosahedral phase (Ψ-Al₆Cu₂Fe) which has unprecedented struc- tural perfection and no apparent phason strain. The icosahedral phase has equilibrium phase fields with four distinct phases at 700 °C and 720 °C (β-Al(Fe, Cu), λ-Al₁₃Fe₄, ω-Al₇Cu₂Fe, and liquid) and three phases at 680 °C(β, ω, and λ) and 800 °C (β, λ, and liquid). The B2 ordered β phase has considerably greater solubility for Cu than previously reported, extending from AlFe to ∼Al₅₀Fe₅Cu₄₅. The equilibrium range of composition for the icosahedral phase at these temperatures was determined, and a liquidus projection is proposed.