Investigation on the origin of magnetization in plastically deformed Ni51Ti49 alloy

The article deals with the investigation of structure and magnetic properties of plastically deformed Ni51Ti49 alloy. The magnetic hysteresis loops confirm the presence of ferromagnetic properties in the alloy. The transmission electron microscopy (TEM) detects the appearance of lenticular crystals with bending contours which indicate the large distortion of the crystal lattice. The crystal lattice curvature occurs due to the large atom displacement. As a result, icosahedral clusters with the Frank-Kasper (FK) structure can be formed. The spin-polarized density of electron states and the magnetic moments for both non-deformed (near-spherical structure) and deformed (elongated by 5% along the Z-axis) Ni7Ti5 (FK-12), Ni8Ti5 (FK-13), and Ni10Ti6 (FK-16) clusters are calculated for the explanation of possibility of magnetization appearance in Ni51Ti49 alloy. The calculations show the increase in the magnetic moments for the deformed clusters. The calculated spectra demonstrate the high density of electron states near the Fermi level which is a characteristic feature of ferromagnetic alloys

Магнитные свойства в пластически деформированном никель-титановом сплаве

Ni–Ti alloy has been intensively studied over the past decades. The unique properties of the alloy have allowed using it as a structural material for the creation of instruments and devices in various fields of science and technology, including mechanical engineering, aerospace, instrumentation. Measuring magnetic hysteresis loop is shown that after the deformation of the alloy having ferromagnetic properties. According to the equilibrium phase diagram, the alloys of Ni–Ti at a Ti content above 10 at. % is non-ferromagnetic. Due to lowering of the crystal phase symmetry with a cubic lattice the magnetization appears. In this work we have investigated the magnetic properties and the structure of deformed Ni51Ti49 samples by electron microscopy and X-ray diffraction methods. In Ni51Ti49 samples after plastic deformation the lenticular crystals containing bending contours with a high concentration of internal stresses were found. Bending contours indicate a large distortion of the crystal lattice. The curvature of the crystal lattice occurs due to the large displacements of the atoms. As a result, it can be formed and icosahedral cluster with the structure of the Frank–Kasper. An icosahedron is a twelve vertex polyhedron, which is denoted by FK-12. Furthermore, the crystal can be formed in other Frank–Kasper structures, e. g., FK-16. FK-16 is a sixteen vertex polyhedron with atom located in the center of the cluster. Indexing paintings electron diffraction and X-ray showed that the alloy phase of the Ni–Ti coexist with the structure Ti2Ni and Ni4Ti3. For explaining the possibility of the appearance of magnetization in Ni–Ti alloy samples spin-polarized electron density of states and magnetic moments Ni10Ti6 clusters (FK-16), Ni7Ti5 (FK-12) alloy Ni51Ti49 for electrons with different spin projections: “up” and “down” was calculated. The calculation by the scattered waves (RF) was performed. The results of calculation can be seen that the total electron density of nickel tends to zero faster than the density of titanium. Also shows that nickel becomes negative spin density in the area of r = 3.25–6.7 a. u. and titanium for r > 4.5 a. u. This may result depending on the value of the interatomic distances and to the effects ferromagnetism and antiferromagnetic in order to establish a magnetic clusters. The spectra show a high density of states near the Fermi level that is a characteristic feature of metals, besides there is an increase in the magnetization of the alloy during deformation. The calculations showed that the investigated clusters, not susceptible to deformation, also have a magnetic moment (the average magnetic moment per atom cluster FK-12, is about 1,0 μB, and for the FK-16 is about 0.3 μB. Overall, however, the average magnetic moment is zero, due to the absence of a preferred direction (the chaotic distribution of clusters) for the alloy. However, if the cluster is subjected to tension, the compensation of the magnetic moments of clusters occurs in the alloy, since there is allocated for all atoms direction due to deformation. At the same time, the average magnetic moments of the atoms in the cluster for the Deformed increase to 1.6 μB and 0.8 μB respectively for the FK-12 and FK-16

The Study of the Fine Structure of Ti-Al Coatings on the Surface of Ti, Obtained by Mechanical Alloying

The work is devoted to the study of structural-phase transformations in composite coatings (Ti-Al)+Ti during mechanical alloying. The data on the structural-phase states of (Ti-Al)-Ti coatings after mechanical alloying have been obtained, confirming the mechanism of formation of the modified layer due to deformation compaction of powder particles on the titanium surface under mechanical action. As a result of mechanochemical fusion, a TiAl3 phase with a bcc lattice (I 4/mmm structure) was detected, which corresponds to the stable state of the TiAl3 alloy. Under conditions of mechanical alloying of the structure, I4/mmm transforms into the L12 structure, which corresponds to the metastable state of TiAl3

Сталь 110Г13Л. Термомагнитные и гальваномагнитные эффекты в ее пленках

The article shows the ability to control magnetic properties due to modulation of phases in the film with varying temperature of growth. So, at low growth temperatures, a film is formed with an axis of easy magnetization in plane. An increase in temperature leads to a change in the phase composition of the film. It is shown that the presence of even a small component of the magnetization vector in the perpendicular direction leads to the appearance of a thermomagnetic effect of a large magnitude with respect to thermal noiseВ статье показана возможность управления магнитными свойствами за счет модуляции фаз в пленке при варьировании температуры роста структуры. Так, при низких температурах формируется пленка с осью легкого намагничивания в плоскости. Повышение температуры приводит к изменению фазового состава пленки. Показано, что наличие даже небольшой компоненты вектора намагниченности в перпендикулярном направлении приводит к возникновению термомагнитного эффекта большой относительно тепловых шумов величин

Иcследование тонкой структуры Ti-Al покрытий на поверхности Ti, полученных методом механического сплавления

The work is devoted to the study of structural-phase transformations in composite coatings (Ti-Al)+Ti during mechanical alloying. The data on the structural-phase states of (Ti-Al)-Ti coatings after mechanical alloying have been obtained, confirming the mechanism of formation of the modified layer due to deformation compaction of powder particles on the titanium surface under mechanical action. As a result of mechanochemical fusion, a TiAl3 phase with a bcc lattice (I4=mmm structure) was detected, which corresponds to the stable state of the TiAl3 alloy. Under conditions of mechanical alloying of the structure, I4=mmm transforms into the L12 structure, which corresponds to the metastable state of TiAl3Работа посвящена исследованию структурно-фазовых превращений в композиционных покрытиях (Ti-Al)+Ti при механическом сплавлении. Получены данные о структурно- фазовых состояниях (Ti-Al)-Ti покрытий после механического сплавления, подтверждающие механизм формирования модифицированного слоя за счет деформационного уплотнения частиц порошка на поверхности титана под механическим воздействием. В результате механохимического сплавления обнаружена фаза TiAl3 с ОЦК-решеткой (структура I4=mmm), что соответствует стабильному состоянию сплава TiAl3. В условиях механического сплавления структура I4=mmm переходит в структуру L12, что соответствует метастабильному состоянию TiAl3