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Test results of Al/SiC whiskers composites production by squeeze casting method and information on particularities of SiC whisker preforms production method are given in this presentation. The mechanism of aluminium melt penetration into whisker preform and also chemical processes occuring on fiber/matrix interface were studied. Basic requirements, ensuring composite quality billets production, were presented here.

The practical feasibility and advantages are demonstrated of a method for the production of a dispersion-strengthened nickel-chromium alloy consisting in diffusion chromizing of nickel and subsequent diffusion annealing of the resultant material. It has been established that disperse hafnium dioxide particles have an inhibiting effect on the diffusion of chromium in dispersion-strengthened nickel. It is shown that chromium diffusion does not disturb the directional character of the structure of the structure of dispersion-strengthened nickel.

Metallographic and x-ray spectral studies of alloy powders subjected to mechanical alloying in a planetary centrifugal mill for various periods of time have shown that the high intensity of alloying in this type of mill enables the duration of the process to be reduced to between one-fifth and one-seventh that necessary with the attritors normally used for this purpose. A study was made of the structure and mechanical properties of rods of a dispersion-strengthened Ni-W-Al alloy produced by extrusion of a mechanically alloyed powder. The rods were found to be characterized by a high degree of structural homogeneity, an elongated grain shape resulting from active directional recrystallization during annealing, and a high level of strength at temperatures of up to 1200°C.

1. Carbon fibers in contact with a magnesium-base matrix experience no loss of strength during heating for 100–500 h at temperatures up to 400–450°C. In contrast to the aluminum-carbon-fibers system, 5-min contact with molten magnesium in the temperature range 660–780°C brings about no loss of fiber strength; interaction between the phases in this case is apparently restricted to diffusion across the interfaces. 2. In the temperature range 450–660°C carbon fibers vigorously react with a magnesium-base matrix, as a result of which their strength falls. The loss of strength suffered by carbon fibers during heat treatment for 100 h at 550°C may amount to 60–70% of their starting strength; under these conditions the cross-sectional area of the fibers decreases by 15–20%.

1. The Orowan strengthening mechanism in dispersion-strengthened alloys remains operative up to high temperatures. For alloys processed under the same conditions a linear relationship is observed between their long-time rupture stress and the reciprocal of the mean interparticle spacing. 2. In the determination of the mean interparticle spacing it is necessary to take into account the volume fraction distribution of particles. 3. For a qualitative evaluation of the heat resistance of an alloy, use may be made of the relative volume fraction of coarse strengthening particles.

1. In composite material of the Al-B system spherical inclusions of AlB2 are formed on the surface of the filaments at points where the protective film of Al2O3 on the aluminum foil is destroyed. 2. Inclusions of AlB2 greatly reduce the strength of the filaments and also weaken the bond with the matrix. 3. At all diffusion welding temperatures there is a certain period of time (incubation period) in which no AlB2 is formed. 4. The duration of the incubation period does not depend on the pressure during diffusion welding, while the rate at which AlB2 is formed in the following period depends to a considerable extent on the pressure. 5. The processes occurring in the incubation period are diffusional in character and evidently associated with destruction and coalescence of the oxide film; the presence of oxygen (pressing in air or use of previously oxidized boron filaments) accelerates the process of coalescence.

1. The most objective data upon the size of particles in dispersion-strengthened alloys are provided by electron diffraction microscopy. 2. The method of extraction and subsequent electron microscopical examination of particles ensures high reliability in determinations of particle size parameters and enables analysis to be carried out at any stage of alloy preparation. 3. The x-ray method of determination of mean particle sizes gives reliable results when few inclusions more than 1000 A in size are present. The method can also be recommended for the evaluation of relative changes in the size of strengthening phase particles under the action of various factors. In investigations of this type, the presence of a large number of coarse particles is not an obstacle.

1. In the manufacture of VKA-1 composite material the diffusion welding of the semifinished product is accompanied by the formation at the fiber/matrix interfaces of the AlB2 phase in the form of spherical inclusions at sites of Al2O3 film disintegration on the matrix foils. 2. To each diffusion welding temperature there corresponds a certain period of time during which no AlB2 phase is formed at the fiber/matrix interfaces. 3. A method of assessing the defectiveness of the surfaces of reinforcing fibers is described, which can be effectively employed for studying the reaction in the CM, particularly its early stages.

1. A uniform distribution of ultrafine strengthening phase particles in starting powders imparts high thermal stability to dispersion-hardened nickel. 2. The level of high-temperature properties attained in dispersion-hardened nickel depends on the presence of a certain proportion of oriented recrystallized regions in the structure of the material and is adversely affected by the presence of equiaxed grains. 3. A nonuniform distribution of strengthening phase particles in starting powders increases the mean particle size in the resultant dense material and alters the character of recrystallization, leading to the formation of equiaxed grains.

Durch Erhitzen von Gemischen aus Seltenerdmetall- und Zr-nitrat wurden die Oxide (I) erhalten, die Fluoritstruktur besitzen.