Heat treatment induced intermetallic phase transition of arc-sprayed coating prepared by the wires combination of aluminum-cathode and steel-anode

A method to prepare intermetallic composite coatings employing the cost-efficient electric arc spraying twin wires assistant with suitable heat treatment was developed. In this study, a Fe-Al composite coating was produced by spraying twin wires, i.e. a carbon steel wire as the anode and an aluminum wire as the cathode. The inter-deposited Fe-Al coating was transformed in-situ to Fe-Al intermetallic composite coating after a post annealing treatment. The effect of annealing treatment conditions on phase composition, microstructure and mechanical properties of the coating was investigated by using XRD, SEM, EDS and OM as well as microhardness tester. The results show that the desirable intermetallic phases such as Fe₂Al₅, FeAl and Fe₃Al are obtained under the annealing condition. The main oxide in the coating is FeO which can partially transform to Fe₃O₄ up to the annealing condition.     

A CEMS investigation of57Fe+Al implanted in Al foil

⁵⁷Fe implanted and post Al implanted in aluminum foil have been performed at low energy of 27keV and the CEMS shows the formation of intermetallic compounds FeAlσ and Fe₂Alσ during the ion bombardment. The results are discussed with the enhanced diffusion by energetic ion bombardment.     

Electronic structure of the intermetallic compounds Ce2Fe17 and Ce2Fe15.3M1.7 (M = Al, Si): Experiment and theory

The electronic structure of the intermetallic compounds Ce₂Fe₁₇ and Ce₂Fe_15.3 M _1.7 (M = Al, Si) is theoretically calculated in the local-spin-density approximation. It is shown that a considerable increase in the Curie temperature upon introduction of Al and Si impurities is accompanied by a proportional increase in the exchange interaction parameters J _ij within the Heisenberg model for iron ions in the 6c crystallographic positions. The experimental optical conductivities of the compounds under investigation are interpreted in terms of the calculated electronic structure. The experimental valences obtained for the cerium ions from an analysis of the Ce L ₃ x-ray absorption spectra indicate that cerium in these intermetallic compounds is in intermediate valence states. Original Russian Text ? A.V. Lukoyanov, A.S. Shkvarin, Yu.V. Knyazev, Yu.I. Kuz’min, A.G. Kuchin, N.N. Efremova, L.D. Finkel’shteĭn, I.A. Nekrasov, V.I. Anisimov, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 1, pp. 95–101.     

Alloying of cold-sprayed Al-Ni composite coatings by post-annealing

A new cold spray coating technique for thick Al coating with finely dispersed Al-Ni intermetallic compounds was tested. For easy powder preparation and high yield, rather than using of Al/compound mixture feed stock, the spraying of pure Al and Ni powders mixture followed by post-annealing was suggested. The powder composition of Al and Ni was 75:25, and 90:10 (wt.%) to expect full consumption of pure Ni into intermetallic compounds. After Al-Ni composite coatings, the Ni particles were finely dispersed and embedded in the Al matrix with a good coating yield. Above 450 °C of post-annealing temperature, the Al₃Ni and Al₃Ni₂ phases were observed in the cold-sprayed Al-Ni coatings. The Ni particles in the Al matrix were fully consumed via compounding reaction with Al at 550 °C of the annealing temperature.     

Phase evolution of an aluminized steel by oxidation treatment

Effects of temperature and time on the microstructure and phase evolution for different thermal treatments were investigated with respect to the measurement of intermetallic layer thickness, phase identification and microhardness distribution in the aluminized zone of a steel substrate. The intermetallic phases present in the aluminized region after hot dip aluminizing is mainly Fe₂Al₅. The thickness of the intermetallic layers increases with increasing oxidation temperature and time. In the oxidation treatments of the aluminized steel in air, the initial Fe₂Al₅ phase remains at the temperature below 950 °C in 2-h, and the Fe₂Al₅ phase is completely transformed into low iron content Fe-Al intermetallics due to oxidation at 950 °C for 4 h. However, the Fe₂Al₅ phase remains in the outer layer of the aluminized samples diffusion-treated in vacuum regardless of diffusion time. The microhardness values of the Al₂O₃ and the intermetallic Fe₂Al₅, FeAl₂, FeAl and Fe₃Al phases are HV1150, HV1010, HV810, HV650 and HV320, respectively. The oxide layer formed on the steel substrate has an extremely fast adherence to the steel substrate and excellent properties of thermal shock resistance, high temperature oxidation resistance and anti-liquid aluminum corrosion.     

Microstructure evolution process of Ferro-Aluminum based sandwich composite for electromagnetic shielding

In this paper, sandwich composite (SWC) with Fe–Al soft magnetic alloy sandwiched between pure iron substrates was proposed and fabricated by hot pressing and diffusion treatment. The microstructure evolution process of the composite was investigated. Fe/Fe₂Al₅/Fe diffusion couple was obtained at 700 °C and subsequently kept at 900 °C for further isothermal diffusion. During the diffusion reactive process, we confirmed that major FeAl₂ and minor Fe₄Al₁₃ were produced when Fe₂Al₅ dissolved. After 10 h of diffusion treatment, FeAl and α-Fe(Al) were the only two intermetallic phases left. Except FeAl₂, the thickness of each intermetallic layer held good parabolic relationship with the diffusion annealing time.     

Influence of argon ion bombardment on the formation of intermetallic compounds in the nickel-aluminum system

The formation of Ni _x Al _y intermetallic compounds in two-layer (Ni/Al) structures (nickel films deposited on aluminum substrates in vacuum) under bombardment by Ar⁺ ions has been studied experimentally. The method based on Rutherford backscattering of He⁺ ions is used to demonstrate that argon ion bombardment causes the formation of intermetallic compounds in the near-surface layer. The thickness of the intermetallic layer formed in the near-surface region substantially exceeds the projective ion path. The composition and thickness of the intermetallic layer depend mainly on the implantation dose and the substrate temperature, rather than on the ion current density. In the intermetallic layer, the content of nickel increases with increasing temperature. It has been established that, in the absence of bombardment, intermetallic phases are not observed at temperatures lower than T = 400°C and that, in the presence of bombardment, the Ni₃Al intermetallic layer arises at a temperature of 320°C.     

Amorphization of the intermetallic compounds Co2Zr and Fe2Zr under mechanical grinding

The crystalline intermetallic compounds Co₂Zr and Fe₂Zr were produced in the stoichiometric composition and milled in a planetary ball mill for different milling periods. The samples were investigated in respect to the question if a crystal-to-glass transition occurs due to the milling process. Three different experimental methods were used for this study: X-ray diffraction, Mößbauer spectroscopy, and measurements of the specific heat capacityc _p . The intermetallic compound Fe₂Zr is very suitable for this study since it is ferromagnetic at room temperature. Thus it shows characteristic features in the Mößbauer spectrum and in the measurement of the specific heat capacityc _p . The investigation shows that the intermetallic compounds Co₂Zr and Fe₂Zr undergo a crystal-to-glass transition under mechanical grinding but the X-ray diffraction patterns show that the transformation is not complete. Even after long milling periods always an amount of a crystalline phase is present in the milled samples. In comparison the mechanically ground samples show the same properties as mechanically alloyed powder mixtures of the two elements of the same chemical composition. A probable explanation for the development of an amorphous phase by mechanical grinding of the crystalline compounds Co₂Zr and Fe₂Zr is the accumulation of internal strain in the crystalline grains. Another possible explanation, the addition of iron impurities to the crystalline compounds due to the wear debris of the milling equipment, seems to be improbable since the intermetallic phases Co₂Zr and Fe₂Zr show extended existance ranges in the equilibrium phase diagrams and hence are stable in respect to a variation in the composition.     

TDPAC study of mechanically alloyed amorphous andintermetallic Fe-Hf alloys

Time differential perturbed angular correlation spectra of the amorphous Fe₅₇Hf₄₃ alloy prepared by mechanical alloying (MA) andthe intermetallic compounds FeHf₂ were measured. The short-range structures in amorphous Fe₅₇Hf₄₃ andintermetallic compounds of FeHf₂ andFe₂Hf are compared from a microscopic point of view.     

Redistribution of chromium atoms between the components of an intermetallic/oxide nanocomposite in the course of its production

Structural studies of nanocomposites produced by the method combining mechanical preactivation of the mixture comprising 8.1% Cr₂O₃, 65.9% Fe, and 25% Al by mass and self-propagating high-temperature synthesis (SPHTS) have been carried out by Mössbauer spectroscopy methods. It was found that a Fe/Al/Cr₂O₃ composite with a small Fe₂Al₅ intermetallic impurity is produced at the mechanical activation stage. At the SPHTS stage, interaction between the activated components of the mixture results in formation of the Fe_0.70?x Cr _x Al_0.3/Al₂O₃ (x = 0–0.2) composite.     

A study of the electronic structure of Fe3C,Fe3Al and Fe3Si by x-ray photoelectron spectroscopy

The core levels and valence bands of Fe₃C, Fe₃Al, Fe₃Si and their pure components at temperatures ranging from 20 to 1000° have been investigated. Shifts in Fe 2p$\text{3}\text{2}$, C 1s, Si 2p and Al 2p confirm the migration of electrons from iron to carbon and from aluminium and silicon to iron. A study of the valence bands of these compounds shows that their electronic structure is determined, in the first approximation, by the type of the second component atoms.     

Hydrogen absorption and its effect on the magnetic properties of rare-earth iron intermetallics

X-ray diffraction studies of the hydrogen absorption in several YFe and CeFe intermetallic compounds showed that no structural changes occur upon hydrogen absorption in Y₆Fe₂₃, YFe₃, YFe₂. The lattice constants of the hydrides were found to be appreciably larger than those of the pure intermetallic compounds. The magnetic properties of the hydrides were determined and compared with the original compounds. In all cases the magnetic moment per Fe atom proved to be much larger in the hydride phases. Hydrogen absorption can lead to a decrease as well as to an increase of the magnetic ordering temperature (T_c). These changes in T_c could adequately be explained in terms of the observed increases in lattice constant and the data available for the pressure derivative of T_c of these compounds.     

Mössbauer investigation of the magnetic anisotropy and electronic structure of a metallic glass

The magnetic anisotropy of a Fe₈₀B₂₀ (METGLAS 2605) metallic glass has been investigated by Mössbauer spectroscopy. The direction of magnetization is shown to be strongly temperature dependent with an unusually large out-of-plane component. The similarities between the electronic structure of this glassy alloy and the Fe₂B and FeB intermetallic compounds are discussed briefly.     

Magnetic properties of rare earth-transition metal compounds

A survey is given of results obtained by means of rare earth and⁵⁷Fe Mössbauer spectroscopy on intermetallic compounds of rare earths (R) and 3d metals (M). It is shown how these results can be used to obtain experimental information on crystal field effects, magnetic anisotropy, magnetic moments and magnetic coupling constants. The types of compounds considered in this review comprise RM₅, R₂M₁₇, R₂Fe₁₄B, R₂Fe₁₄C, R₂Fe₁₇C _x and RFe₁₀V₂. The results obtained by Mössbauer spectroscopy are compared with other techniques and the discussion of relevant theoretical models is included.     

Mössbauer and X-ray diffraction studies of mechanically alloyed Fe-Al

Powder samples of Fe₂₅Al₇₅ were prepared by the mechanical alloying method. Mössbauer effect, X-ray diffraction and DSC measurements indicate that Fe and Al crystalline powder transform into Fe-Al amorphous powder with increasing milling time. The X-ray diffraction patterns of the milled Fe₂₅Al₇₅ do not clearly show a sign of the existence of the intermetallic phases or Fe-Al solid solution. However, Mössbauer measurements reveal two sites with hyperfine magnetic fields 30.2 and 26.0 T. These sites form locally during the milling process and then they disappear.     

Phonon spectra of <Emphasis Type="Italic">L</Emphasis>1<Subscript>2</Subscript> Ni<Subscript>3</Subscript>Al and <Emphasis Type="Italic">B</Emphasis>2 NiAl: Ab initio calculations

Phonon spectra and phonon density of states of intermetallic compounds Ni₃Al and NiAl are studied using the ab initio linear-response method. The calculated phonon dispersion curves agree well with the inelastic neutron scattering data available for the crystals under study.     

Investigation of magnetic properties in 57Fe/Al multilayers

Fe/Al multilayer thin films prepared by ion beam sputtering, with an overall atomic concentration ratio of Fe/Al = 1:2 have been studied by x-ray diffraction spectroscopy (XRD), X-ray reflectivity (XRR) and D.C. Magnetization. These studies show the formation of Fe–Al intermetallic layers. Two magnetic regions and transition temperatures of 473 and 533 K are evident from magnetization studies. Conversion Electron Mössbauer Spectroscopy (CEMS) shows formation of off-stoichiometric Fe₃Al like phase and phases consisting of pure Fe and Fe-rich extended Fe–Al solutions.     

Ordering of atoms in 3d sublattice of the intermetallic quasibinary system Dy(Fe1−xMnx)2

Methods of x-ray analysis and nuclear -resonance (Mössbauer effect) have been used to study the distribution of iron and manganese atoms in the intermetallic quasibinary system Dy(Fe_1–xMn_x)₂, which is isostructural to the Laves phase C15. Ordering of atoms of transition metals has been found in 3d sublattice of intermetallic compounds Dy(Fe_1–xMn_x)₂ with the formation of a triple superstructure having the stoichiometric composition Dy(Fe_0·.25Mn_0·.75)₂.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 55–60, June, 1986.     

Zur Supraleitung einiger Mischsysteme von Verbindungen mit A15-Struktur auf Vanadiumbasis

Ternary intermetallic compounds on the base of V₃Ga and V₃Si have been prepared by arc melting, substituting gallium and silicon partly by aluminium, gallium, indium, silicon, and germanium. In similar way part of the niobium in the compounds Nb₃Al and Nb₃Ga has been replaced by vanadium. All these ternary compounds have been investigated for superconductivity. Only by substituting gallium in V₃Ga partly by aluminium or silicon, the transition temperature could be raised.     

Interdiffusion,reaction, and stability in a thin film iron-aluminium bilayered system

In this work we describe the results of Rutherford backscattering spectrometry, sheet resistivity measurements, X-ray diffractometry and conversion electron Mössbauer spectroscopy performed on thin film Fe-Al bilayered samples submitted to high vacuum furnace annealing. Isothermal anneals were performed at 570 K for time intervals ranging from 60 to 600 min. It is demonstrated that the diffusion of Al into Fe is smaller than the diffusion of Fe into Al for temperatures below 600 K. Sequential isochronous thermal anneals of 60 min were performed at temperatures ranging from 570 to 870 K, in order to study the stability of the formed phases. The stable Fe₂Al₅ intermetallic compound formed at 570 K decomposes at about 650 K, and the FeAl₆ intermetallic compound appears at temperatures around 750 K.Work supported in part by CNPq and FINEP