Powder Metallurgy and Metal Ceramics (v.55, #1-2)

Ultraviolet Laser Cleaning of Carbon Fiber Composites by R. Delmdahl; J. Brune; R. Pätzel (1-4).
Carbon fiber reinforced plastics (CFRPs) are composite materials that offer a highly desirable combination of physical strength and light weight. Originally developed primarily for aerospace applications, they can now be found in products ranging from automobiles, sailboats, and racing bicycles to golf clubs. Adhesives are often used to join individual CFRP pieces in an assembly because bonding offers several advantages over mechanical fastening methods. However, achieving a high strength adhesive bond can be frustrated by the presence of surface contaminants. A variety of techniques have been employed to clean CFRPs prior to bonding, but each of these methods has limitations in terms of either speed, complexity or the need for subsequent cleaning. Excimer laserbased surface cleaning and ablation now offers a practical alternative which yields a pristine surface with the requisite characteristics for adhesive bonding. This article reviews how excimer laser cleaning is implemented and discusses the results of bond strength testing performed using this technology.
Keywords: excimer laser; carbon fiber composite; pretreatment; adhesive bonding

Effect of the Deformation Scheme on the Structure and Properties of Hot-Forged Aluminum-Matrix Composites by Yu. A. Shishkina; G. A. Baglyuk; V. S. Kurikhin; D. G. Verbylo (5-11).
The structure and mechanical properties of aluminum-matrix composites, produced by hot forging of billets consisting of Al and 15 wt.% TiC–20% Al master alloy powder mixture, are investigated. Cylindrical and hollow cone billets are used for forging. It is shown that both strength and hardness of the composites produced from conical billets noticeably exceed those of the materials produced from cylindrical billets. In comparison with cylindrical billets, the use of conical billets for forging leads to an increase in (i) the intensity of deformation and (ii) the microhardness of the matrix phase.
Keywords: aluminum-matrix composite ; forging ; strain intensity ; strength ; hardness ; structure

Finite-Element Optimization of the Asymmetric Rolling Process for Titanium Powder by I. Yu. Prikhod’ko; M. A. Dedik; K. A. Gogaev; V. S. Voropaev; A. I. Itsenko (12-18).
The selection of resistance-to-deformation model is analyzed and justified. The results of mathematical modeling for the asymmetric rolling of titanium powder using the finite-element method are demonstrated.
Keywords: asymmetric rolling; titanium powder; mathematical modeling; finite-element method

The papers focusing on experimental and theoretical studies on sintering kinetics of real powder systems that were published in the 1940s–1950s are analyzed. Two major concepts explaining the nature of the so-called activity shown by metallic powders and some inorganic powders during sintering are addressed in detail. One concept deals with the key role of plastic flow mechanism and the other gives preference to the role of crystal lattice defects formed in powder particles when produced in nonequilibrium conditions. The reasons why neither of the concepts can underlie the physical theory of active sintering, being in full agreement with the experiment, are ascertained.
Keywords: sintering; densification kinetics; plastic flow; crystal lattice defects

Effect of Coo Microadditive on the Properties of ZrO2–Y2O3–CeO2–Al2O3 Nanocrystalline Powder by V. V. Tsukrenko; A. K. Ruban; V. P. Red’ko; E. V. Dudnik (29-36).
The changes in the physical and chemical properties of ZrO2–Y2O3–CeO2–Al2O3 nanocrystalline powder with 0.2 wt.% CoO microadditive during thermal processing in the 400–1300°C temperature range are investigated. It is shown that CoO microadditive reduces the specific surface area of the powder and significantly affects the temperature range of the F-ZrO2 → T-ZrO2 phase transformation. The morphology changes topologically continuously. The phase transformation in the ZrO2–Y2O3–CeO2–Al2O3 system occurs in the 850–1150°C temperature range. In the presence of CoO microadditive, this range is 700–850°C.
Keywords: zirconia; alumina; cobalt oxide; phase transformation; nanocrystalline powder

Selective Oxidation for Quantitative Determination of Free Carbon Nanoforms in Boron Carbide Powders by V. V. Garbuz; L. M. Kuz’menko; L. S. Suvorova; V. A. Petrova; T. A. Silinskaya; S. K. Shatskikh (37-42).
A technique for direct determination of free carbon nanoforms present as impurities in boron carbide powders has been developed. This technique substantially enhances the existing instrumental methods and can be used for developing ISO standards for qualification of carbon nanomaterials.
Keywords: boron carbide; free carbon nanoforms; sequential oxidation; coulometry

The hardness of cobalt powder alloys in the ‘room temperature–1150°C’ temperature range is investigated. The alloys are prepared by hot pressing of cobalt, chromium, aluminum, and iron powders with titanium or niobium carbides. The hardness of the alloys strengthened with 30 to 50 vol.% carbide at various temperatures show that the amount of the strengthening phase affects the hardness of the alloys investigated. The most significant factor that affects the hardness of the alloys is the temperature factor: with increasing temperature the hardness reduces regardless of the type and content of the carbides. It is shown that the hardness of the alloys with titanium carbide exceeds the hardness of those with niobium carbide. These results could be used to create friction materials for aviation purposes.
Keywords: hardness; temperature; cobalt alloys; titanium carbide; niobium carbide

Structure and Properties of Titanium Carbide Based Cermets with Additives of Other Carbides by T. P. Grebenok; T. V. Dubovik; M. S. Kovalchenko; L. A. Klochkov; A. A. Rogozinskaya; V. I. Subbotin (48-53).
The properties of wear-resistant cermets based on titanium carbide with additives of other carbides produced by two techniques are investigated. These techniques are: pressure sintering of powder mixture of the starting components (TiC, VC, Mo2C, NbC, Ni, and Cr) and pressure sintering of powder mixture of pre-synthesized solution of the starting carbides ((Ti, V, Mo, and Nb)C with additives of Ni and Cr. It is determined that cermets produced by the second technique possess more homogenous and fine-dispersed structure. The latter determines its higher mechanical strength, hardness, crack resistance, heat stability, and wear resistance, in comparison with the properties of cermets produced by the first technique.
Keywords: titanium carbide ; mixture ; hard solution ; pressure sintering ; structure ; cermet

The effects of Fe and Cu on the wear behaviour of W–Ni alloys is investigated. W–Ni–Fe and W–Ni–Cu alloys are produced with six different compositions by the powder metallurgy technique. The microstructure is examined after shaping and sintering. Electron microscopy (SEM+EDS) and X-ray diffraction (XRD) are used to characterize the density, hardness, and grain size of W–Ni–Fe and W–Ni–Cu alloys produced by powder metallurgy technique. A pin-on-disc apparatus is used for the wear tests. All of the samples are tested under loads of 20 and 30 N, at a rate of 1 m/s and for five different sliding distances. It is found that, in Fe and Cu alloys, an increase in the W amount results in an increase in density and hardness. Furthermore, an increase in the W amount leads to a decrease in the amount of the binding phase for W–Ni–Fe and W–Ni–Cu alloys with a W content of 90, 93, and 97%, and resultes in reduced weight loss for W–Ni–Fe alloys.
Keywords: tungsten heavy alloys ; powder metallurgy ; characterization ; liquid phase sintering ; wear behavior

Alloy Constitution and Phase Equilibria in the Hf–Ru–Rh System. III. Solidus Surface of the Partial Ru–HfRu–HfRh–Rh System by L. S. Kriklya; K. E. Kornienko; V. G. Khoruzhaya; V. M. Petyukh; L. A. Duma; V. B. Sobolev (64-71).
The data obtained by metallography, X-ray diffraction, and electron microprobe and differential thermal analyses, as well as incipient melting points measured with the Pirani-Althertum method, are used to construct, for the first time, the solidus surface of the Hf–Ru–Rh system at 0–50 at.% Hf on the composition triangle. Ruthenium and rhodium solid solutions, ε and θ phases based on HfRh3 (AuCu3-type structure) and Hf3Rh5 (Ge3Rh5 type), and a continuous series of solid solutions between isostructural (CsCl type) phases based on the HfRu compound and its high-temperature modification (δ phase) take place in phase equilibria. Five single-phase surfaces corresponding to solid solutions based on components and binary phases, seven ruled surfaces bounding the two-phase volumes, and three isothermal planes formed by the mentioned phases in invariant four-phase equilibria with participation of liquid (at 1900, 1810, and 1720°C) are constituents of the solidus surface.
Keywords: solidus surface; phase; compound; isothermal plane; ruled surface

Vertical Sections of the Al2O3–HfO2–La2O3 Phase Diagram by S. M. Lakiza; Ya. S. Tishchenko; L. M. Lopato (72-77).
For more complete description of the Al2O3–HfO2–La2O3 phase diagram, three vertical sections are constructed in a wide temperature and composition range. Isopleth 20 mol.% HfO2 (20H) shows the Al2O3–HfO2–La2O3 constitution in the Al2O3-rich region. Isopleth 60 mol.% HfO2 (60H) describes the ternary system in the Al2O3- and La2O3-rich regions and F ⇄ T phase transformation of HfO2 solid solutions. The radial La2O3–(50 mol.% Al2O3 · 50 mol.% HfO2) vertical section reveals the nature of X ⇄ H ⇄ A phase transformations of La2O3 solid solutions. The vertical sections intersect all three triangulating planes of the Al2O3–HfO2–La2O3 system and demonstrate variation in the width of their two-phase regions.
Keywords: ceramics; hafnia; alumina; lanthana; interaction; vertical sections; eutectic materials

Thermodynamic Properties of Binary Al–Pr Alloys by M. O. Shevchenko; V. V. Berezutskii; M. I. Ivanov; V. S. Sudavtsova (78-90).
The mixing enthalpies of Al–Pr binary liquid alloys are measured in the ranges 0 < x Pr < 0.15 at 1560 K and 0.46 < x Pr < 1 at 1410–1670 K by isoperibol calorimetry. The Al–Pr binary melts are characterized by significant negative mixing enthalpies: Δ H A l − Pr min $$ varDelta {H}_{Al- Pr}^{{}^{min}} $$ = –43.1 kJ/mol at x Pr = 0.33 (at 1500 K, extrapolation onto the range of supercooled melts). The activities of components, entropies, Gibbs energies, and liquidus curve of the Al–Pr phase diagram are evaluated using the model of ideal associated solutions.
Keywords: calorimetry ; mixing enthalpies ; aluminum ; praseodymium ; ideal associated solution model

Structure and Properties of TiAl-Based Alloys Doped with Niobium and Chromium by M. V. Remez; Yu. M. Podrezov; A. A. Bondar; V. Witusiewicz; U. Hecht; V. M. Voblikov; N. I. Tsyganenko; Ya. I. Yevich; T. Ya. Velikanova (91-108).
Quaternary as-cast Ti 96–x Nb 2 Cr 2 Al x and Ti 93–x Nb 5 Cr 2 Al x alloys, where x = 44, 46, 48, and 50, melted from pure components (~99.9 wt.%) in a laboratory arc furnace, were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), and differential thermal analysis (DTA). Bending testing and fracture toughness measurements were performed at room temperature, and compression testing was carried out in a range from room temperature to 750°C. The alloys were found to consist mainly of a superfine lamellar structure formed during decomposition of hightemperature phases. In addition, the alloys with 50 at.% Al contain grains of the γ phase, and all others have precipitates of the cubic β/β 0 phase at boundaries of the high-temperature phases because of double enrichment of the last melt drops with Cr. The tests show that the Ti 96–x Nb 2 Cr 2 Al x alloys with 46 and 48 at.% Al possess the most balanced properties.
Keywords: TiAl ; lamellar structure ; strength ; ductility ; Al–Cr–Nb–Ti ; phase constituents

Effect of Copper on the Formation of Ordered L10(FePt) Phase in Nanosized Fe50Pt50/Cu/Fe50Pt50 Films on SiO2/Si (001) Substrates by T. I. Verbitskaya; E. V. Figurnaya; M. Yu. Verbitskaya; I. A. Vladymyrskyi; S. I. Sidorenko; E. P. Pavlova; Yu. N. Makogon (109-113).
The effect from thickness of an intermediate copper layer in nanosized Fe50Pt50 (15 nm)/Cu (x)/Fe50Pt50 (15 nm) (x = 7.5, 15, and 30 nm) composite films on SiO2 (100 nm)/Si(001) substrates on the diffusion-controlled phase formation processes—transformation of the disordered magnetically soft A1(FePt) phase into the ordered magnetically hard L10(FePt) phase during annealing in vacuum—is studied by physical materials science methods: X-ray diffraction and measurement of magnetic properties. The A1(FePt) phase forms in all films during deposition. Annealing in vacuum in the temperature range 300–900°C is accompanied by thermally activated diffusion processes between the Cu and FePt layers. When thickness of the intermediate Cu layer increases from 7.5 nm up to 15 nm, the onset temperature of A1(FePt) → L10(FePt) phase transformation raises by 100°C, i.e., to 800°C. Simultaneously, the coercivity in films decreases since Cu dissolves in the FePt lattice.
Keywords: ordered L10(FePt) phase; annealing; intermediate layer; coercivity

A historical overview of the origin and evolution of ferrous metallurgy, fundamentals of producing iron and its alloys, is presented. The paper shows the sequence of discoveries behind the technology of iron and steel, the effect of carbon on the formation of cast iron and steel, as well as the progress in foundry and thermomechanical treatment of iron alloys, which promoted the development of large-scale production that laid the foundation for industrial development and material basis of civilization.
Keywords: iron; cast iron; steel; casting; forging; forge welding; tempering; annealing; bulat steel; Iron Age; cutting tool; cold steel arms; coat of mail; light weapons; guns; Siemens–Martin process; basic oxygen furnace process; blast-furnace process