V. V. Mukhgalin

Deformation-induced changes in the structure of fullerites C60/70 during their mechanical activation

Structural changes occurring during the mechanical activation of fullerites C60/70 have been investigated using X-ray diffraction, IR and UV spectroscopy, and scanning electron microscopy. The complete destruction modes of fullerite have been determined (3.5 h at the intensity of the mill of 4.3 W/g and 28 h at 2.2 W/g). The destruction of the crystal structure of fullerites is accompanied by the destruction of fullerene molecules. The residual solvent, which enters into the composition of C60/70, is retained during the entire time of mechanical activation. In this case, the low-frequency shift of absorption bands of toluene (729 → 725 cm−1), which is caused by the deformation of the solvent molecule in the composition of crystal solvates, has been observed. It has been shown that the deformation stability of graphite is substantially lower than in the case of fullerite.

Structural and phase transformations in aluminum-copper alloys under the effect of electroplastic deformation

The deformational structure and the phase composition of binary and commercial aluminumcopper alloys produced using electroplastic deformation by rolling (EPDR) have been studied. It has been shown that structural transformation in the materials and changes in their hardness in the course of EPDR are governed by the initial state, which determines the distribution and the thermomechanical stability of a dislocation ensemble. It has been found that EPDR causes the dynamic deformation-induced aging of the aluminum-based supersaturated solid solution, which is accompanied by the precipitation of the strengthening θ phase in the Al-Cu alloy and the S phase in the D16 alloy.

IR-Fourier spectroscopic studies of structural changes in fullerenes C60 and C70-Toluene systems

The C60-toluene and C70-toluene complexes were studied by IR-Fourier spectroscopy. The complexes were obtained by crystallization from a toluene solution at room temperature. The changes in the IR spectra caused by the deformation of toluene molecules in the complexes allowed us to study the phase transitions in the fullerene-aromatic solvent systems.

Stacking faults and mechanisms strain-induced transformations of hcp metals (Ti, Mg) during mechanical activation in liquid hydrocarbons

The evolution of the structure and substructure of metals Ti and Mg with hexagonal close-packed (hcp) lattice is studied during their mechanical activation in a planetary ball mill in liquid hydrocarbons (toluene, n-heptane) and with additions of carbon materials (graphite, fullerite, nanotubes) by X-ray diffraction, scanning electron microscopy, and chemical analysis. The temperature behavior and hydrogen-accumulating properties of mechanocomposites are studied. During mechanical activation of Ti and Mg, liquid hydrocarbons decay, metastable nanocrystalline titanium carbohydride Ti(C,H)x and magnesium hydride β-MgH2 are formed, respectively. The Ti(C,H)x and MgH2 formation mechanisms during mechanical activation are deformation ones and are associated with stacking faults accumulation, and the formation of face-centered cubic (fcc) packing of atoms. Metastable Ti(C,H)x decays at a temperature of 550°C, the partial reverse transformation fcc → hcp occurs. The crystalline defect accumulation (nanograin boundaries, stacking faults), hydrocarbon destruction, and mechanocomposite formation leads to the enhancement of subsequent magnesium hydrogenation in the Sieverts reactor.

Accelerated mechanosynthesis of high-nitrogen stainless steel: Mössbauer and X-ray diffraction studies

A completely austenitic structure has been obtained ten times faster via the mechanical alloying (MA) of high-nitrogen 25Cr10Mn1N alloy from metal components and manganese nitride than during the MA of similar steels in a nitrogen atmosphere. A mechanism for the bcc → fcc phase transformation that occurs during MA, and where deformation stacking faults of the layer fault type on the {211} atomic planes of the bcc phase play a key role, is considered and proposed.

Effect of deformation on the structural state of piracetam

The effect of various deformation actions on the structure–phase transformations in piracetam of modifications I and II with a sodium acetate addition is studied. Mechanical activation and pressing are shown to cause the polymorphic transformation of modification I into modification II, and modification III forms predominantly during severe plastic deformation by torsion. The structural difference between the piracetam molecules of modifications I and II is found to be retained in aqueous solutions.

Phase separation and crystallization process of amorphous Fe78B12Si9Ni1 alloy

The influence of the melt heat treatment on the structure and crystallization process of the rapidly quenched amorphous Fe78B12Si9Ni1 alloys have been investigated by means of x-ray diffraction, DSC and TEM. Amorphous phase separation has been observed in the alloys quenched after the preliminary high temperature heat treatment of the liquid alloy (heating above 1400°C). Comparative analysis of the pair distribution functions demonstrates that this phase separation accompanied by a changes in the local atomic arrangement. It has been found that crystallization process at heating is strongly dependent on the initial amorphous phase structure - homogeneous or phase separated. In the last case crystallization goes through the formation of a new metastable hexagonal phase [a=12.2849(9) Ǻ, c=7.6657(8) Ǻ]. At the same time the activation energy for crystallization (Ea) reduces from 555 to 475 kJ mole−1.

Heat treatment effect on amorphization and structure of Fe80B13Si5C2 melt in ultrarapid quenching

X-ray diffraction, differential scanning calorimetry, and differential thermal analysis are used to investigate the superheating-temperature effect of a Fe80B13Si5C2 melt on its supercooling, amorphization ability, and the crystallization processes of rapidly quenched alloys during subsequent heating. The melt is found to reach the maximum supercooling and the highest amorphization ability after heating in the temperature range of 1450–1480°C. It is revealed that, when heated to 1500°C, the supercooling and amorphization ability of the melt decrease sharply.