L. E. Bodrova

Interaction between vanadium carbide and aluminum and copper melts

The effect of low-frequency vibrations on the interaction between molten metals (Al,Cu) and vanadium carbide is studied. These vibrations are shown to initiate wetting of the V8C7 carbide by a copper melt and a chemical interaction in the Al-V8C7 system, resulting in the formation of vanadium aluminides and aluminum carbide.

Al-Ti-Zr master alloys: Structure formation

The effects of the composition of ternary Al-Ti-Zr master alloys, the overheating of their melts with respect to liquidus, and exposure to low-frequency vibrations on the structure formation in them are studied. It is shown that complex aluminide Al3(ZrxTi1 − x) with a metastable L12-type cubic lattice coinciding with the structure type of α Al primarily precipitates during the crystallization of Al-Ti-Zr melts under certain conditions. This fact makes such master alloys promising for modifying aluminum alloys.

Synthesis of niobium carbides in copper melts

The production of cast composite Cu-NbC alloys by synthesizing of niobium carbides in a copper melt is studied. The processes of carbide formation are intensified by the mechanical activation of niobium and graphite powders, which are mixed with a copper melt, in a high-speed ball mill and by the action of low-frequency vibrations on copper melts.

Interaction of tungsten with tungsten carbide in a copper melt

The chemical interaction between tungsten and tungsten carbide in a copper melt with the formation of W2C at 1300°C is studied. It is shown that the mechanical activation of a composition consisting of copper melt + W and WC powders by low-temperature vibrations initiates not only the chemical interaction of its solid components but also their refinement.

Carbide formation in aluminum melts processed by low-frequency elastic vibrations

The temperature and time conditions of carbide formation in binary aluminum melts subjected to elastic low-frequency vibrations transferred through a graphite vibrating piston are studied to develop an in situ technology for the production of composite materials. Our experiments demonstrate that the carbide-forming abilities of components dissolved in aluminum cannot be estimated from the changes in the standard free energies ΔGT of formation of their carbides from pure elements. Although energies ΔGT of formation of titanium and zirconium carbides from pure elements are close, only titanium dissolved in aluminum has a high carbideforming ability. This specific feature is used to synthesize titanium carbides in an aluminum melt and to produce aluminum-based composite materials hardened by titanium carbides.

Al-Sc-Zr Master Alloy and Estimation of Its Modifying Capacity

An Al-1.1 Sc-1.1 Zr (wt %) master alloy with a uniform distribution of micron and submicron particles of aluminide phase Al3(Sc1 − xZrx) has been obtained by exposing of equal amounts of commercial Al-Sc and Al-Zr master alloys to short-time actions of low-frequency vibrations transferred to the alloy via an irradiating plunger. Zirconium substitutes up to 50% Sc in aluminides and retains its L12 lattice. The modifying capacity of the experimental master alloy is tested on cast alloy (wt %) Al-8Zn-2.4Cu-3Mg. Intense grain refinement of this alloy is achieved by its modification with a certain amount of the master alloy. At a certain Sc + Zr content, a grain dendrite structure completely disappears in the alloy.

Structure of Al-Ti-C master alloys

A binary Al-Ti master alloy of hyperperitectic composition, whose structural characteristics ensure high modifying efficiency, has been prepared by the aluminothermy method. The treatment of the alloy by low-frequency vibrations (LFVs) and its interaction with the carbon emitter of LFVs in the process of crystallization lead to the formation of a ternary Al-Ti-C alloy containing titanium aluminide Al3Ti and titanium carbide TiC. The presence of these phases creates favorable conditions for the formation of solidification nuclei in the aluminum melt when using a ternary master alloy as a modifier. A comparison of the efficiency of the structure refinement when using experimental master alloys and the standard Al-Ti master alloy poured into a metallic chill mold has been performed.

Effect of time-temperature and low-frequency acoustic treatments of the melt on the structure formation in the Al-5% Fe alloy

Regularities of the structure-formation in the Al-5% Fe alloy under conditions of time-temperature and low-frequency acoustic treatments are studied. A 500-K overheating of the melt above the liquidus temperature was found to cause a sharp change in the conditions of formation of the solid phase at the solidification front and to initiate the formation of a metastable quasi-eutectic structure. An additional low-frequency acoustic treatment increases the effect of the melt undercooling. This leads to the formation of anomalous growth forms of the solid at the lower overheatings of the melt.

Optimization of Liquid-Phase Method of Synthesis of Cu–W Alloys

Cu–W composite alloys are obtained using the liquid-phase impregnation method of noncompacted W powders and sintered porous W and W + Cu specimens. The structure of the alloys and its influence of pre-crystallization processing by low-frequency oscillation (LFO) on the “Cu melt–W powder” compositions are investigated. The technological parameters of obtaining low-porosity (1–2%) alloys are defined. It is proved that varying the thermo-time LFO exposure makes it possible to modify the W concentration in the matrix, creating the composite layers with high tungsten content (80–90%). The LFO treatment of the “copper melt + noncompacted W powders” compositions has a number of advantages compared to the routine (liquid-phase impregnation of compacted tungsten powder) industrial technology of production of Cu–W alloys. There are significant reduction of stages (up to 1–2), the possibility of replacement of working atmospheres (hydrogen, vacuum) by cheaper “Ar + CO,” and the dispersion of W phase.

Interaction of niobium and tungsten monocarbides in molten copper

The chemical interaction of uncompacted monocarbide NbC and WC powders, which were taken at mass carbide ratios NbC: WC = 10: 1, 3: 1, 1: 1, and 1: 3 and a total carbide content of 20 wt %, in molten copper is studied at 1300°C. The primary and secondary phase transformations that result in the appearance and decomposition of an (Nb,W)C solid solution are analyzed. The activating role of low-frequency vibration is shown.