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1. An investigation into the temperature dependence of the strength of a niobium/tungsten-wire composite, which constitutes a typical ductile-matrix/ductile-fiber system, has shown that at high temperature (> 1000°C) there is a discrepancy between the experimentally determined strength of the composite and values of strength calculated with the additive equation. 2. The extra strength of the composite is due to a “plasticizing” influence exerted by the niobium matrix on the tungsten fibers, as a result of which the latter undergo additional strain strengthening. 3. Fractographic examinations revealed that the rupture of a Nb/W composite is preceded by substantial local plastic deformation of its components.

Addition of pyrophyllite to the system of corundum concrete produced using phosphate binders leads to a reduction in the temperature of setting (hardening) up to room temperature, an increase in the strength at moderate temperatures (up to 973°K), a significant resistance to softening in the 973–1273°K range, and an improved thermal shock resistance.

1. It has been confirmed that the curve of strength vs transition zone thickness for a composite consists of two distinct portions: I) a portion of structural stability, within which an increase in layer thickness does not lead to a loss of strength of the composite, and II) a portion characterized by loss of strength. 2. It has been established that the fibers of an aluminum/steel-fiber composite subjected to a tensile load fracture in a tough manner within the limits of portion I and in a brittle manner within the limits of portion II.

con. The chemical composition of the initial powders is shown in Table 1 and their specific surface, determined by the method of low-temperature adsorption of nitrogen, is given in Table 2.

The purpose of this work was a detailed study of the interaction with hydrogen of the titanium-alloy (magnesium-lithium) pseudoalloy and also investigation of the process of hydrogenation of pseudoalloys of titanium with intermetallides of magnesium (Mg-Ni, Mg-Cu, Mg-Y, Mg-La) traditionally used for adsorption of hydrogen. The hydrides were decomposed in heating to 1173/sup 0/K in vacuum. The temperature of the start of liberation of H/sub 2/ was recorded at the moment when the hydrogen pressure above the hydride reached 500 Pa. The structure of the specimens was studied on a Reichert optical microscope and on a JEM-U3 scanning electron microscope. The composition of the hydride phase was determined by x-ray diffraction.

An expression relating H toα and d has been derived, with the aid of which it is possible to select an optimum interfiber spacing in the production of monolayer coatings. The deposit layer height has been found which is necessary for obtaining, after pressing, material of minimum porosity. An angle of inclination of the nozzle has been selected which enables good-quality deposits to be applied to substrates.

1. A compact of a material from knitted gauzes constitutes, because of its loop structure, a spring-like fibrous'skeleton exhibiting a targe elastic aftereffect, which manifests itself even in the course of sintering. 2. In the production of materials of low porosity and predetermined thickness it is preferable to employ a process consisting of double sintering with intermediate pressing, which enables pressing to be carried out at a lower pressure and facilitates the attainment of the required thickness. 3. Sintering under pressure is the most effective method of producing high-porosity materials of predetermined thickness from knitted gauzes. 4. The strength of vacuum-sintered porous materials from knitted gauzes grows as their sintering temperature approaches the melting point of the material of their fibers. The optimum sintering time lies in the range 2.5–3.5 h. 5. During sintering in a vacuum partial loss of material from the fiber surfaces is observed, the extent of which grows with increase in porosity.

The sound absorbing properties of the PFM(C) depend on such parameters of the material as porosity, fiber diameter, type of wire interlocking in the starting bonded semifinished product, and number of fibers in the yarn of the semifinished product. By suitable choice of fiber diameter, type of interlocking, and number of wires in a yarn, it is possible to attain an optimum porosity, which ensures a value of coefficient of sound absorption close to unity. Decreasing the fiber diameter shifts the optimum porosity toward higher values. Use of bonded semifinished products with a looser type of fiber interlocking leads to the maximum of sound absorption being observed at slightly higher porosities. When the active impedance component is greater than the wave resistance of air, the coefficient of sound absorption can be increased by increasing the number of fibers in the yarn of the gauze semifinished product.

1. The wear resistance of titanium, under dry friction conditions can be appreciably increased by employing the metal in the form of composites infiltrated with low-melting-point metals and alloys. 2. In the friction and wear investigation described the best combination of bearing properties was found to be exhibited by a Ti-(Bi-Pb-Sn-Cd) material with a metallic lubricant content of 20–25 vol.%. The optimum duration of infiltration, involving immersion in molten metal, was 60 min. In the load range investigated the operating performance of the material improved with increasing sliding speed.

1. A method is proposed for calculating the CTE of composite materials reinforced with unidirectionally oriented fibers, in which account is taken of the elastic-plastic behavior of the components of the composites. 2. The relationships derived were verified by experiments on VZh98 alloy reinforced with tungsten fibers, which showed good agreement between calculated and experimental values of CTE. 3. Allowing for the internal stress set up in a composite material as a result of elastic-plastic behavior of its components makes it possible to explain the shape of the CTE vs temperature curve of the composite.

1. An investigation into the sintering kinetics of reinforced hard magnetic materials has shown that the sintering of such materials occurs in two stages. In the first stage (1 h) compacts exhibit swelling, and in the second stage they shrink. Reinforced composites swell more than do unreinforced materials, which is attributable to relief of internal stress during heating. The residual porosity of composites is greater than that of unreinforced compacts. The reason for this is that the fibers impede the volume deformation of the matrix. 2. The impact strength of reinforced magnets grows linearly with increase in reinforcing fiber concentration and diameter. An increase in impact strength is determined by the work done in the pulling out of fibers from the matrix. At constant fiber concentration the highest value of impact strength is exhibited by composites reinforced with fibers whose length-to-diameter ratio is close to the critical ratio.

1. On the basis of an investigation into the kinetics of infiltration of porous titanium by liquid magnesium and magnesium alloys it has been established that the infiltration rate constant grows with increase in pore size at any given porosity and with rise in total porosity of specimens being infiltrated. The rate of infiltration is virtually independent of temperature, within the range investigated, and of magnesium alloy composition. 2. The results obtained lead to the conclusion that the kinetics of infiltration of porous titanium by magnesium obeys the basic laws of the theory of capillary infiltration.

The authors have developed a procedure for obtaining compact corundum materials, reinforced with filamentary mullite crystals, with a high heat resistance. They have determined the optimal content of filamentary mullite crystals in the composite.

1. Increasing the wire diameter has a slight deleterious effect on the strength properties of materials fabricated from knitted gauzes. 2. With a material produced from unidirectionally arranged gauzes, the strength in the direction of loop rows is different from that in the direction of loop columns. The difference grows with increasing porosity. Cross stacking gives intermediate values of strength properties. 3. The directional anisotropy of the shear strength of the material may be employed as a characteristic of its porosity anisotropy. 4. Because of the continuity of its fibers the material possesses excellent ductility. In bending tests specimens with porosities greater than 70% are able to bend with-out cracking until their sides are parallel. 5. The material exhibits little notch sensitivity. Changing the radius of a stress raiser in the material from 1 to 0.1 mm has virtually no effect on its impact strength.

Sintering of powdered high-speed steels to the poreless state proceeds under conditions of short-term appearance of liquid phase; this entails the formation of low melting phases in consequence of the segregation of the alloying elements and carbon on the surface of the powder particles. To obtain material with less than 1% porosity it is necessary to use powder with mean particle size not exceeding 80 μm.

Thermal spraying enables protector alloy coatings to be deposited possessing the required properties for the protection of low-carbon steel against corrosion. The optimum protector properties are exhibited by a coating containing aluminum and magnesium in the ratio 3∶1.

The corrosion resistance of 40KhN2MA steel was analyzed under hydrostatic pressure using data collected by an electrochemical and corrosion test and measurement cell. Tests were performed using distilled water at 293/sup 0/K and hydrostatic pressures up to 80 MPa. Corrosion rates were determined by polarization resistance. Anode and cathode potentiodynamic curves were also recorded. Corrosion was irregular and appeared due to pitting. Screen electron microscopy and x-ray microanalysis were used to determine surface behavior. Hydrostatic pressure inhibited the dissolution of the steel components and thus decreased the rate of corrosion. Increases in pressure also changed the oxidation-reduction properties and ionic composition of the water.

By changing the wire diameter from 30 to 90 Μm, the number of wires in a strand from 1 to 40, and the porosity from 0.35 to 0.77, it is possible to obtain PGMs from bound lastingweave gauzes covering wide ranges of structural and hydraulic characteristics. The coefficient of variation of the mean pore size of PGMs ranges from 0.02 to 0.17, and that of the maximum pore size from 0.043 to 0.18, in the porosity range 0.35–0.77 for materials from 1-, 3-, and 6-wire strand gauzes of wire diameters 50 and 70 ym. The coefficient of variation of the coefficient of permeability of PGMs changes from 0.02 to 0.11 in the porosity range 0.40–0.77.

1. For aluminum reinforced with steel fibers, increasing the fiber concentration to 50–60 vol. % produces only a small increase in the electrical resistivity of the composite. At higher fiber concentrations the rate of ascent of theϱ vs Vf curve sharply increases. 2. For titanium base composites reinforced with molybdenum fibers, at low reinforcing phase contents (of the order of 10–20 vol.%) the electrical resistivity of the composites decreases by a factor of more than 2 to 3 compared with the resistivity of the matrix. Subsequently, the rate of fall ofϱ slows down. 3. The experimental curves of resistivity vs composition and temperature for all the composites investigated are similar in character to the curves obtained analytically; however, the experimental values are slightly higher than the calculated results, by 3–4% for the aluminum base composites and by 10–12% for the titanium base composites.

1. A study was made, by the methods of metallographic examination, electron probe microanalysis, and x-ray phase analysis, to ascertain whether the components of Mg—B and Mg—steel composites produced by plasma spraying of the matrix material on fibers and subsequent densification by hot pressing (diffusion welding) react with each other. 2. It was established that, within the limits of resolving power of the techniques employed, no fiber/matrix interface reactions occur in such Mg—B and Mg—steel composites under the densification and annealing conditions investigated.

The authors assess the porosity and fracture properties of porous samples of molybdenum, tungsten, and steel-Kh18N9T through a variety of mechanical tests including impact, bend, and notch. They study the interplay and interdependence of these properties in view of looking for materials suited for processes of transpiration cooling and sound and vibration damping.

1. A spectroscopic study was made of the reactions of several metals (Al, Cu, Ni, Co, Ti, Mo, W, and Kh18N9T steel) with silicon dioxide in the as-deposited condition and after annealing in the temperature range 600–1500°C. 2. In the contact reaction of SiO2 films with metallic surfaces up to the maximum temperatures of existence of these films, no individual metallic oxides or similar chemical compounds (such as olivines) are formed. 3. The temperature limits of stability of SiO2 films applied to various metallic substrates have been established. The most stable systems, remaining unchanged right up to 1450°C, are Mo-SiO2 and W-SiO2. 4. The reaction in metal-SiO2 film systems at temperatures below the film stability limits is limited to a polarizing action of the metallic substrate, which manifests itself in the appearance of additional absorption bands in the ranges 1320–1260 and 520–500 cm−1.

1. It has been established that the short-term static strength of silicon carbide fibers follows a normal distribution law. 2. Young's modulus obtained from the additivity law for the direction of reinforcement of unidirectional and biaxially reinforced (1:1) SCRP agrees satisfactorily with the experimental value. 3. The strength of the fibers used governs the strength properties of the composites and is used (at 80–90%) in the optimum technology of creating a material. 4. The impact strength of plastics containing silicon carbide fibers is 7–14 kgf·cm/cm2 and the fatigue strength for pulsed flexure is approximately 0.45 of the static flexural strength.

1. Experiments were carried out on the production of a porous material from lasting-type mesh stainless steel gauzes by pressing and sintering. 2. An investigation has demonstrated that the structural characteristics of specimens of PGMs from gauzes with this type of mesh are determined by the number of wires in the loop and the porosity of the PGMs. 3. A study was made of the hydraulic resistance of specimens of stainless steel PGMs. It has been established that the loss of pressure of the medium accompanying the filtration of air through the PGM is determined by the number of wires in the loop, the degree of deformation experienced by the PGM during its manufacture (porosity), and the Reynolds number of the air stream in the pores.

In this paper are given the results of phase transformation kinetics and the more significant thermodynamic properties of materials based on silicon nitride during heating in air up to 1670/sup 0/K and higher depending on the amount of the phosphate binder (PB) and introduced additives (aluminum and zirconium oxides).

Modern plant construction requires materials having outstandingly high strength-weight ratios and the attention of research workers is being attracted more and more to fiber-reinforced plastics, which combine high strength and stiffness with low density, resistance to corrosive media, and suitability for the industrial fabrication of components. Plastics reinforced with glass fibers have already found fairly wide application but their use is restricted owing to their inadequate stiffness. Enhanced stiffness of composite materials can be obtained if high-modulus fibers (carbon, boron, silicon carbide, etc.) are used as reinforcements [I, 2].

The character of diffusional interaction of the components of tungsten-reinforced heat-resisting sheet composite materials produced by hot forging with subsequent plastic working depends on the latter's degree of plastic deformation. The loss of chromium from the surface of such a CM varies depending on the degree of plastic deformation and on the composition of the matrix alloy. Tungsten fibers stabilize the composition of a CM by acting as obstacles in the paths of chromium diffusion fluxes.

Composite materials based on the thermodynamically unstable systems Zr-Mo and Zr-W have satisfactory kinetic stability of the structure up to 1373°K. At higher temperatures there occurs intense interaction between fibers and matrix entailingthe formation of solid solutions and intermetallic phases. The course of the diffusion processes in the investigated CM is determined by the history of their components, and this makes it possible to a certain extent to control these processes by corresponding preliminary thermomechanical treatment of the components.

The hardening of compositions based on aluminum and silicon nitrides is a result of the chemical reaction of their phosphate binder with the nitrides, while additions of, e.g.,α-corundum act as inert fillers up to a temperature of 570‡K. The reaction products are amorphous acid mono- and disubstituted aluminum and silicon phosphates, which on heating at first condense, forming poly- and metaphosphates, and then, at temperatures above 870‡K, decompose, forming (depending on their composition) aluminum orthophosphate or silicon pyrophosphate.

A method of calculation is proposed which makes it possible to predict the useful lives of pseudoalloys operating under various conditions. As the boiling front penetrates into the skeleton of a pseudoalloy, the effect of the enthalpy properties of its filler on the working surface temperature, which determines the service life of the material, diminishes. When experimental data are available on the temperature distribution in time and space for a specimen, the model may be employed for solving a reverse problem, viz., determination of operating conditions.