G. A. Baglyuk

Effect of the Deformation Scheme on the Structure and Properties of Hot-Forged Aluminum-Matrix Composites

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.

Effectiveness of Jet Milling for Producing Superfine Powders from Blast-Furnace Slag

The paper examines the effect of ball (drum) grinding and jet milling on the particle size distribution and specific surface area of the powders produced from blast-furnace slag. The effectiveness of jet milling, providing relatively equal powder particles (more than 85% of the fractions is 0–10 μm in size), is shown. Decrease in the average particle size leads to greater specific surface area of the powder and to a sharp increase in activity (strength of the samples prepared with use of blastfurnace slag). Hydraulic activity σ ≥ 30 MPa can be reached by the powder produced from slag with an average particle size to 12 μm and specific surface area S = 0.6–0.8 m2/g, which increases the sample strength. The strength of cemented compositions based on blast-furnace slag can be improved to 40–43 MPa by adding 15–20% Portland cement to the starting mixture.

Effect of carbon and aluminum contents on the structurization of Al–Ti–C powder master alloy during reaction synthesis

The paper presents results of electron microprobe, X-ray diffraction, and differential thermal analyses of master alloys produced by reaction synthesis of Al–Ti–C powder mixtures of various compositions. It is shown that heating of all stating mixtures leads to in situ precipitation of titanium carbide particles and complex titanium–aluminum carbides. Spherical titanium carbide particles are the predominant strengthening phase in samples with high carbon content (10–13%) and disordered elongated acicular grains of complex titanium–aluminum carbides in samples with minimum carbon content (6%) and relatively high aluminum content (40%). It is established that 45 wt.% Al–11 wt.% C–44 wt.% Ti master alloy with practically equal aluminum and titanium contents is characterized by the finest strengthening phase particles after thermal synthesis.

The structure and phase composition of boride coatings on sintered powder steels

Results of metallographic and X-ray diffraction analyses of boride coatings produced by saturation of porous blanks from iron–carbon powder alloys are provided. It is established that the structure and phase composition of boride coatings made of iron–carbon powder alloys depend on the composition of borating mixtures: the amount of diffusion activator AlF3 in the borating mixture essentially influences the structure, phase composition, and hardness of the coating and a higher amount of the activator intensifies the borating process, leading to the formation of a very hard coating and borocarbides in the transition zone.

Features of Structurization During Sintering of Compacts from a Multicomponent Ti–Cr–Fe–Ni–Cu Charge

A heterophase alloy with hardness 103 HRB and a porosity of ~5% is produced by sintering compacts from a Ti–Cr–Fe–Ni–Cu multicomponent charge. It is demonstrated that after sintering a mixture of elemental powders, four phases with different types of lattice are formed: (i) two multicomponent phases with FCC-lattice, (ii) one Cr–Fe phase with BCC-lattice, and (iii) one phase with HCP-lattice with crystallographic constants based on titanium lattice. Well-defined peaks of Cr2Ti, Fe2Ti, and Ni3Ti intermetallides are seen in the X-ray photograph of the alloy.

Interaction between Fe–Ti–B4C Powder Charge Components During Heating

The structurization of compacted Fe–Ti–B4C powder mixtures during reaction synthesis is studied. X-ray diffraction of the material synthesized at 1200°C shows the presence of TiC and TiB2 phases formed in the interaction of titanium with carbon and boron resulting from the dissolution of B4C particles in the liquid phase and the interaction of iron with boron. The reaction between titanium, iron, and carbon (boron) is accompanied by a significant exothermic effect confirmed by the presence of two exothermic peaks on the DTA curve at 1085°C (corresponding to the eutectic formed in the Fe–Ti system in the interaction of respective mixture particles on contact surfaces) and 1236°C (resulting from the formation of titanium diboride and carbide particles from the liquid phase).

Simulation of the Equal-Channel Angular Extrusion of Porous Blanks using Different Deformation Patterns

The results from simulation of equal-channel angular extrusion of sintered porous blanks with use of different deformation patterns are presented. It is shown that the maximum equidensity and the minimum volume of the poorly compacted area are observed in the pattern with a movable bottom plate of the die horizontal channel and with backpressure on the sample portion being extruded. This deformation pattern is also determined by the maximum values of deformation force.

Effect of the Silicon Introduction Method on the Structurization of Sintered Fe–Si–C and Fe–Si–B–C Steels

The methods to introduce silicon into Fe–Si–C and Fe–Si–B–C powder composites and its distribution in the alloy matrix are studied. Two types of silicon-containing additions, such as silicon carbide and low-carbon ferrosilicon, may be used. Silicon carbide promotes more uniform distribution of silicon in the iron matrix of the composites, while ferrosilicon leads to better compaction. Selective doping of individual phase components of the Fe–Si–B–C alloys is established: in particular, silicon diffuses only in the iron matrix and does not interact with the boron eutectic.

Strained State of Porous Preforms during Hot Forging in a Die with a Cone-Shaped Flash Gutter

Coordinate grids are used to understand how the strained state of porous preforms evolves during hot forging in a semi-closed die with a cone-shaped flash gutter. The nature of strain tensors and the irregularity of porosity distribution over the forged pieces at various forging stages are established.

Variation in the particle size of FE–TI–B4C powders induced by high-voltage electrical discharge

The effect of high-voltage electrical discharge (ED) on the particle size of Fe–Ti–B4C powders in a hydrocarbon liquid is studied. It is shown that high-voltage ED allows significant refinement of the powders. The important factors are integral processing energy and pressure in the discharge channel. A relationship between the integral processing energy and decrease in the average diameter of micropowder particles is found. It is shown that the average particle size monotonically decreases up to a certain value of integral processing energy. The use of high-voltage ED for the refinement of micropowders permits significant reduction in time and energy needed to reach the desired particle size compared with other methods.