Preparation and Properties of Highly‐Porous Rolled Product Based on Nichrome Powder

A production scheme is suggested for forming strips with a pore forming agent using high-temperature sintering followed by rolling compaction. This makes it possible to prepare highly-porous thin rolled strip based on nichrome powder with a controlled biporous structure and optimum physicomechanical properties.     

Mechanico-Chemical Synthesis,Structure and Properties of Alloys Based on the System Ti ― Al

The kinetics of structure and phase formation in Ti Al and Ti Al Sc alloy powders in the process of mechano-chemical synthesis from elemental powders was investigated. It was established that the formation of microdimensional x-ray amorphous composite particles with nanodimensional structural components occurs. It was shown that in consolidation of the mechanically alloyed powders by hot isostatic pressing structural heredity is realized, and that the materials produced have unusually high microhardness compared to that of similar cast alloys. This is characteristic of nanostructured materials. In addition to high hardness the materials are characterized by high work of plastic deformation at room temperature. Microalloying the alloy powders with scandium has a complex positive effect on the strength properties of the hot pressed materials, due to the formation of a dispersion hardened microstructure with purified nanodimensional grains.     

Effect or Porous Billet Forging Temperature on Parameters of the Fine Structure of the Ferritic Phase in Powder Carbon Steel

The effect of forging temperature for a porous billet made of SP90 steel on the fine structure parameters of the ferrite phase crystal lattice is studied. Harmonic analysis of the form of x-ray lines is used to establish the sharp reduction in material structural defects in surface layers at the punch compact interface compared with core material and the nonuniform nature of the dependence of the levels of defects on deformation temperature.     

Strength and Heat Resistance of New Antifrictional Powder Metallurgy Materials Based on Nickel

The hightemperature strength and heat resistance of new powder metallurgy antifrictional materials based on the powder metallurgy nickel alloy É:P975 were investigated. The effect of alloying elements on the structure and properties of the new materials at high temperatures was studied. It is shown that the developed materials can be successfully used in friction units operating at temperatures up to 900°C in air.     

Enthalpies of Mixing in Liquid Alloys of Copper with Hafnium

Enthalpies of mixing of liquid alloys of copper with hafnium were measured at 1650 K in the concentration range 0 < x _Hf < 0.50 by high-temperature isoperibolic calorimetry. The experimental data obtained indicates exothermic effects upon alloy formation, which confirm a strong interaction of the components in copper hafnium melts.     

Electric Rolling of Powder Materials with a Dielectric Phase

The effect of dielectric phase content on the properties of powder matrix composites (Kh20N802M, NPG80, Nibon20) prepared by electric-pulse sintering with rolling is studied. The change in properties is most pronounced in composites with a filler that has greater hardness than the matrix material. The highest specific electrical resistivity, ultimate tensile strength, and a reduction in hardness are achieved with identical volume fractions of components and the maximum exponent in the Joule component of electric current. Use of electric-pulse sintering with rolling makes it possible to prepare strips with a large fraction of nonforming phase, especially from highyield powders.     

Tribological Properties of Hard Alloys Based on Chromium Carbide

Hard alloys of the type KKhN and KKhNF were studied and shown to have low coefficient of friction (f = 0.21-0.17) and wear rate (I = 5.7-7.0 m/km) at sliding velocity 15 m/sec and load 7 MPa, which make them promising for use as antifrictional materials in dry friction units under load. Oxide films formed at the surface of the hard alloys play the role of solid lubricants and decrease frictional losses.     

Theory of Initial Microcavity Growth in a Liquid Metal Around a Gas - Releasing Particle. Part 2. Bubble Initiation Conditions and Growth Kinetics

A theory is presented that includes capillary, hydrodynamic, and diffusion aspects. The main attention is devoted to capillary and hydrodynamic effects. The hydrodynamic process (bubble growth) is governed by a nonlinear integrodifferential equation, whose coefficients are dependent on the surface tension, density, and viscosity of the liquid, and also on the difference between the pressure in the gas within the bubble and that in the surrounding liquid. The gas pressure in the bubble is dependent on the rate of gas release from the inclusion (source). An expression is derived for the bubble radius as a function of time. The theory can be useful for developing the technology of powder materials and foam metals.