Ordering processes and activation energy in Ni3Fe-based ternary alloys

The measurement of electrical resistance () has been used, to study the kinetics of isothermal ordering in the range 200 °–545 ° C in Ni₃(FeMn) alloy quenched from 970 ° C, and the kinetics of ordering at 390 ° C in the alloy quenched from various temperatures in the 600 °–800 ° C range. The sections method and the gradient of the (t) curves were used to find the activation energy for migration and vacancy formation in this alloy on the assumption that the excess vacancies frozen in the alloy by quenching at temperatures above T_c are responsible for ordering. The activation energies for vacancy formation and migration were respectively U₀ = 33 ± 3 kilocal/mole and U_m = 39 ± 4 kilocal/mole, which in total give the activation energy for diffusion Q = 72 ± 7 kilocal/mole in the alloy studied; this approximates to the activation energy for diffusion in pure nickel.     

Oxidation of Ni3Al–Ni3Nb alloys

Conclusions The Ni₃Al–Ni₃Nb alloys are oxidized as a result of the diffusion of oxygen ions toward the interface between the alloy and the oxidation product. This diffusion produces a relatively thick inner layer of complex composition; in addition, diffusion of nickel ions toward the interface between the oxidation product and the gas results in the formation of a thin outer layer of NiO. At any temperature, NiO in the inner oxide is reduced to Ni by niobium atoms. During the initial stages of the oxidation, the reduction occurs at the oxide-alloy inter face; during the later stages, it occurs at the interface between the oxide and the suboxide layer. Protective double oxides of NiO · Nb₂O₅ (t = 700–725 °) and NiO · Al₂O₃ (t = 800–850 °) form in the oxidation product. An -Nb₂O₅ conversion occurs at 825–900 ° and considerably reduces the oxidizability of the alloys. The -Nb₂O₅ lattice probably contains fewer oxygen vacancies than the -Nb₂O₅ lattice and thus has better protective properties.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 75–83, December, 1969.     

Thermal expansion of Ni3Al-Ni3Nb alloys

Temperature dependence of the thermal expansion coefficient () of Ni₃Al-Ni₃Nb alloys was studied. All alloys were found to have an abrupt decrease of in the 500 °–550 ° temperature range. The two-phase, 94 wt.% of Ni₃Nb alloy was shown to have the lowest thermal expansion coefficient.     

Magnetic transformations in Ni-Zn-ferrospinel

An x-ray diffraction analysis of the thermal expansion of the crystal Ni_0.28Zn_0.72Fe_2.0O₄ in the temperature range 90–400°K was performed. It was found that the coefficient of thermal expansion (T) is anisotropic at temperatures T<260°K, and a sequence of magnetic transformations in the region of magnetic ordering was also found. The parameters of the exchange interaction for a given compound were calculated using the model of local spin deviations.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 7, pp. 23–27, July, 1986.     

Some regularities of the fracture of ordered alloys based on Ni3Fe

Some regularities of the fracture of ordered polycrystals of the alloys Ni₃Fe, Ni₃(FeMn), Ni₃FeAl), Ni₃(FeCr), Ni₃(FeCr) are studied. The alloys Ni₃Fe, Ni₃(FeMn), and Ni₃(FeAl) possess low plasticity in the ordered state at the test temperatures T < 100 °C. In the 100–200 ° C temperature range a brittleness-viscosity transition is detected which is analogous to that observed in body centered cubic (BCC) metals and alloys. The transition from the brittle into the plastic state is not accompanied by a change in the metallographic picture of slip. The distinguishing peculiarity of the strain at elevated temperatures is the significant displacement of the grains along the boundaries. The temperature band of the transition from the brittle into the plastic state of ordered alloys in the tempered state (tempering from a temperature below the temperature of the order-disorder transformation) is observed at tempering temperatures above 450 °C (tests at room temperature). The results obtained permit the assumption that a reduction in the plasticity in ordering alloys based on Ni₃Fe is caused by segregation of the impurities along the grain boundaries.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 35–41, June, 1971.     

A study conceening the kinetics of oxidation of the Ni3Ti compound

Conclusions The kinetics of oxidation of the Ni₃Ti compound at temperatures from 650 to 1000 °C follows, essentially, a parabolic time function. The mechanism of this process changes with temperature and exposure time, as is indicated by a deviation from the parabolic mode of oxidation, by the irregularities in the time and the temperature characteristics of oxidizability and of the parabolic rate constant, and by the change in the external appearance of the complexly constituted scale.An intensive formation of TiO₂ grains results in a linear oxidation mode at t 800 °C and a much greater oxidizability at temperatures above 800 °C.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 92–96, December, 1971.     

Magnetic properties of U (Fe x Al1−x )2 and U(Fe y Ni1−y )2 compounds

The results of magnetic measurements and ferromagnetic resonance studies performed on U(Fe _x Al_1–x )₂ and U(Fe _y Ni_1–y )₂ compounds over a large temperature range are reported. The saturation magnetization decreases nearly linearly when substituting Fe by Al or Ni. In the composition range x<0.84 and y<0.81, the compounds are Pauli paramagnets, except in the region with y0.10. For UNi₂ two types of magnetic behaviours are shown. This compound can be both a ferromagnet withT _c =23.5 K and a Pauli paramagnet, depending on the crystal structure. Above the Curie temperatures, the reciprocal susceptibility for the compounds with x>0.84 and y>0.81 obeys a temperature dependence of the formX=X _o+C(T-) ^–1. The effective iron moments decrease when substituting iron by nickel or aluminium. The ferromagnetic resonance measurements show that theg values are not composition-dependent. A linear variation of the mean iron magnetization with the exchange field is observed. Finally, the magnetic behaviour of iron in these compounds is analysed.     

Growth of Ni2Si by rapid thermal annealing: Kinetics and moving species

The growth kinetics is characterized and the moving species is identified for the formation of Ni₂Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a 100 Si substrate. The interfacial Ni₂Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350–450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni₂Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni₂Si formation.     

Mössbauer Studies of Electrodeposited and Ion Beam Mixed Alloy Coatings

CEMS, XMS, XRD and electron microprobe analysis were applied to study electrodeposited and ion beam mixed Fe–Cr–Ni as well as electrodeposited and ball-milled Sn–Cr alloys. In Fe–Cr–Ni alloys with composition 40% Cr and 20–30% Ni a metastable ferromagnetic phase has been found beside a metastable paramagnetic and an equilibrium phase in all deposits. The relative occurrence of the ferromagnetic phase exhibits an increase in the plating temperature range: 30–40°C. With plating temperature an increase of the short-range order in the ferromagnetic phase was observed. The highenergy heavy ion irradiation of Fe–Ni–Cr multilayer produces ferromagnetic and paramagnetic metastable phases. The electrodeposition of Sn–Cr alloys results in metastable Sn–Cr phases. In the case of ball-milling preparation the equilibrium Sn₃Cr₂ phase (=2.3 mm/s, =1.2 mm/s) appears in Sn–Cr alloys. The quantity of the Sn₃Cr₂ phase increases with the milling time.     

Investigation of the recovery and annealing kinetics of deformedα-iron by magnetic measurements

Isochronal annealing experiments in the temperature range 25–700° C revealed the existence of three annealing stages (stages IV, V and VI) in the annealing spectrum of cold-worked Fe-0.006 wt.% C by observing the associated changes in maximum magnetic susceptibility (_max) and magnetic coercivity (H _cr). Stage IV centered around 220° C appears only in the recovery of heavily cold-worked samples, activated by 1.1 eV, is attributed to the free-migration of vacancies. Stage IV disappears in the recovery spectrum of low-deformed samples and is inferred to the complete capture of vacancies originated during plastic deformation by carbon-atoms in the matrix. The recovery stage V, attributed to the dissocation of carbon-vacancy pairs, is found to be activated by an energy 1.8 eV. The binding energy between the carbon atom and vacancy is found to be 0.7 eV. The mechanism responsible for this recovery stage is enhanced by increasing the degree of plastic deformation in the matrix. The recovery stage VI appears above 450° C, activated by 2.8 eV, and the process is related to the climb motion of dislocations during the recrystallization process.     

A new structure of In-based ohmic contacts ton-type GaAs

Electrical, structural and reaction characteristics of In-based ohmic contacts ton-GaAs were studied. Attempts were made to form a low-band-gap interfacial phase of InGaAs to reduce the barrier height at the metal/semiconductor junction, thus yielding low-resistance, highly reliable contacts. The contacts were fabricated bye-beam sputtering Ni, NiIn and Ge targets on VPE-grownn ⁺-GaAs film (1 m, 2 × 10¹⁸ cm^–3) in ultrahigh vacuum as the structure of Ni(200 Å)/ NiIn(100 Å)/Ge(40 Å)/n ⁺-GaAs/SI-GaAs, followed by rapid thermal annealing at various temperatures (500–900°C). In this structure, a very thin layer of Ge was employed to play the role of heavily doping donors and diffusion limiters between In and the GaAs substrate. Indium was deposited by sputtering NiIn alloy instead of pure In in order to ensure In atoms to be distributed uniformly in the substrate; nickel was chosen to consume the excess indium and form a high-temperature alloy of Ni₃ln. The lowest specific contact resistivity ( _c) of (1.5 ± 0.5) × 10^–6 cm² measured by the Transmission Line Method (TLM) was obtained after annealing at 700°C for 10 s. Auger sputtering depth profile and Transmission Electron Microscopy (TEM) were used to analyze the interfacial microstructure. By correlating the interfacial microstructure to the electronical properties, In _x Ga_{1– x}As phases with a large fractional area grown epitaxially on GaAs were found to be essential for reduction of the contact resistance.This work was supported by the National Natural Sciences Foundation of China (NSFC)     

Growth kinetics of antiphase domains in the alloy Ni4Mo

Using the methods of transmission and diffraction electron microscopy, we analyze the laws governing the growth kinetics of antiphase domains in the alloy Ni₄Mo during its isothermal ordering at 840, 800, and 700°C. The size distributions of the antiphase domains as well as the mean size and central moments of the distributions are determined. It is shown that the growth of the antiphase domains obeys the equation Dⁿ-D ₀ ⁿ =Ae^–Q/kT. The value of the parameter n is 2.5 for 840 and 800°C, and 5 for 700°C. By considering the isochronous cross section of the kinetic curves, we calculate the activation energy for the growth of antiphase domains; it equals 65 kcal/mole.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 84–89, January, 1977.     

Deformation hardening and the temperature dependence of the mechanical properties of ternary ordering alloys. Part II

Yield point, hardening factor, and elastic modulus are reported as functions of quenching and test temperatures for the alloys Ni₃(Fe + 3 at% Al), Ni₃(Fe + 3 at% Mn). A maximum is found in the mechanical properties near the critical temperature T_cr; this does not occur for alloys in the disordered state. The deformation aging under load is examined near this maximum and at 200 ° C. A range of linear hardening occurs up to e of 15–18% in ordered alloys, which is replaced by a range of decreasing hardening coefficient at higher . The results are discussed by reference to earlier ones for Ni₃Fe, Ni₃(FeCr). Ni₃(FeMo).     

The Kinetics of the Cd21Ni5 Intermetallic Growth under High Hydrostatic Pressure

The kinetics of growth of the Cd₂₁Ni₅ intermetallic phase in two-layer Cd-Ni samples has been studied at hydrostatic pressures 0.05–0.9 GPa and at temperatures 200–280°C. Arrhenius equations for both interdiffusion through the growing phase layer and the interfacial reaction have been obtained for different pressures. The activation volumes have been found to be 0.9V₀ for interdiffusion and 1.6V₀ for interfacial reaction, where V_{_0} 1.8 × 10_-29m₃ is the average volume per atom in the Cd₂₁Ni₅ lattice. Atomistic mechanisms of intermetallic growth are discussed.     

Effect of elastic stress on the magnetostriction of ferromagnets

An experimental study has been made of the effect of elastic tensile stresses on the magnetostriction curves of polycrystalline nickel, transformer steel, an equiatomic cobalt-platinum alloy, and an Invar iron alloy with 30–40 wt. % nickel. The sign of the magnetostriction changes during the rotation process under the effect of sufficiently high stress. The effect is explained on the basis of the concept of a magnetic rotation texture, developed earlier by one of the authors. A change in the magnetostrictive susceptibility for the paraprocess of the Invar alloy is found to be caused by the stress; the signs of the magnetostrictive constants are determined for the hardened cobalt-platinum alloy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 12, No. 2, pp. 89–94, February, 1969.     

Mössbauer Spectroscopy Study of Iron Nickel Alloys

Three samples of Fe_100–x Ni _x (with x=30, 35 and 40) were prepared by arc melting technique. The Mössbauer spectra of the three samples were collected and analyzed. The spectrum of the sample with x=30 consists of a singlet and a sextet. The singlet component which has isomer shift (IS=–0.08 mm/s) is attributed to a superparamagnetic phase. The value of the magnetic hyperfine field associated with the sextet component, 34.0 T, is consistent with that of -Fe–Ni alloy. In the spectra of the other samples the central line disappears. The magnetic component, used in fitting the spectrum of the sample with x=40 has a hyperfine magnetic field B _hf=30.0 T. This component is assigned to the high-spin -FCC Fe–Ni phase. Two magnetic components of 16.3 T and 27.3 T are used to fit the spectrum of the sample with x=35. The 27.3 T component is associated with the typical high-spin -FCC Fe–Ni phase while the 16.3 T component is associated with a -FCC Fe–Ni phase with magnetic relaxation.     

Diffusion of Al in ion-implanted Pd and Pt

The diffusion coefficients of aluminium have been measured in polycrystalline fcc Pd and Pt. The Al-implanted palladium and platinum samples were annealed at 400°–800 °C and 450°–900 °C, respectively. The aluminium profiles were probed using the nuclear resonance broadening (NRB) technique. Values of (1.41±0.09) and (1.38±0.09) eV for the activation energy and (1.5 _–1.0 ⁺⁵ )×10^–6 and (4 _–3 ⁺¹⁰ )×10^–7cm²/s for the frequency factor were obtained for Al in Pd and Pt, respectively. These anomalous results, compared to the normal impurity diffusion, were checked using also Al-evaporated samples.     

Magnetic susceptibility and electrical conductivity of the highest chromium germanide

Results are given of measurements over the temperature range 80–1000 ° K of the magnetic susceptibility () and the electrical resistivity () of the highest chromium germanide Cr₁₁Ge₁₉. A ferromagnetic spin ordering is indicated at T < 86 ° K. From the (T) dependence and the values of the resistivity, thermo-emf and Hall constant, it is concluded that the compound studied is a semimetal with p-type conductivity.     

Magnetic properties of solid solutions of the system ErxY1−xFe2

The magnetic properties of the system Er_xY_1–xFe₂ (MgCu₂ structure) in the temperature range 80–800°K are investigated. The magnetization and the coercive force H_c are measured as a function of T. For alloys with x= 0.5–1 there is a magnetic compensation point _c. The composition dependence of _c, the magnetic moment of the alloy and of the iron atoms Fe are determined. An H_c anomaly is observed in _c. In order to explain the results obtained, the presence of two types of magnetically active atoms and three types of exchange interaction are included.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 10, pp. 27–30, October, 1982.     

Physical properties of Cr5−XVXSi3 Solid solutions at low temperatures

Conclusions We have studied the temperature dependence of the electrical resistivity, absolute thermo-emf, magnetic susceptibility, and Hall coefficient of Cr_5–XV_XSi₃ solid solutions over the temperature range 78–300K. The results suggest that all the samples studied are Pauli paramagnetics, their conductivity arising from both holes and electrons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 16, No. 7, pp. 134–136, July, 1973.