Fe Solid Solution Research Articles

Study of radiation-stimulated structural phase transformations in iradiated Zr by Mössbauer spectroscopy

The article considers the study of the influence of high-energy singly charged 57Fe ions with energy of 1 MeV, a beam current on the target of ~100 nA, a dose of 5x1016 ion/cm2, on the structural-phase state of zirconium. Using the methods of Mössbauer spectroscopy in transmission geometry (MS), conversion electron Mössbauer spectroscopy (CEMS), and scanning electron microscopy (SEM), we studied the effect of high-energy singly charged 57Fe ions on the structural-phase state of zirconium. The projective ranges of 57Fe ions in zirconium were determined, the number of target atoms subjected to irradiation was calculated, and the number of displacements caused by these ions was estimated. Radiation damage to zirconium materials was simulated by irradiating samples at a charged particle accelerator with probe Mössbauer atoms to obtain nuclear physical data from the zone of influence of these atoms on the structural and phase state of irradiated samples under conditions close to reactor conditions. The electronic state of the implant in these materials was evaluated. The concentration of implanted atoms in the near-surface layer and the volume of samples was calculated. In particular, it was shown that the projective range of 57Fe ions in zirconium was 497 nm, the total number of displaced atoms was 3.4х1020, and the number of displacements per atom (dpa) was 159. The solubility of Fe in Zr is 0.03%. However, when zirconium is irradiated with 57Fe ions, as a result of thermal recombination of vacancies and interstitial atoms within the cascade of displacements caused by thermal peaks, intermetallic compounds Zr3Fe, ZrFe2 and a Zr (Fe) solid solution are formed.

Features and regularities in formation of diffusion nickel-copper coatings on steels in the medium of low-melting liquid-metal solutions

The paper considers the features and regularities of formation of Ni-Cu based diffusion coatings on the surface of steel products obtained as a result of diffusion metallization from the medium of low-melting liquid metal solutions. It was found out that a solid solution of Ni, Cu, Fe was formed in the main layer of coatings after applying the Ni-Cu coating on armco-iron, steel 20 and tool steel Kh12MF; it was characterized by approximately equal concentration of nickel and copper on the coating surface, it made 55 % Ni and 27 % Cu. As soon as the depth of the base layer increases, concentration of Ni and Cu in it gradually decreases, while the iron content also increases. During formation of Ni–Cu coatings on alloyed steels, selective diffusion of steel alloying elements deep into the coating is observed. It is established that the coatings have two layers – the main and the transition ones. At the same time, the maximal coating thickness constitutes 55 μm at the saturation temperature of 1150 °C and 6 hours duration. It was revealed that the main layer consists of Ni, Cu, Fe solid solution, also contains steel alloying elements and consists of columnar grains elongated in the direction of diffusion of the coating elements, as well as in its surface layer with thickness of about 5 μm. The layer of nano-scale grains with a cross-section size of 80-100 nm is forming. During formation of Ni-Cu based coatings, the phenomenon of displacement of the coating carbon and the steel alloying elements into the transition layer is confirmed; these carbon and steel elements do not interact with the coating elements.  The innovation project was conducted under financial support of the Kuban scientific fund within the framework of the Competition of scientific-innovation projects directed on commercialization No. NIP-20.1-62/20.

Morphological and Structural Transformations of Fe-Pd Powder Alloys Formed by Galvanic Replacement, Annealing and Acid Treatment.

In this article, we report the preparation and structural features of Fe-Pd powder alloys formed by galvanic replacement, annealing and selective dissolution of iron via acid treatment. The alloys were studied by the X-ray diffraction phase analysis, Mössbauer spectroscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The Fe@Pd core–shell particles were obtained by a galvanic replacement reaction occurring upon treatment of a body-centered cubic (bcc) iron powder by a solution containing PdCl42− ions. It was found that the shells are a face-centered cubic (fcc) Pd(Fe) solid solution. HCl acid treatment of the Fe@Pd core–shell particles resulted in the formation of hollow Pd-based particles, as the bcc phase was selectively dissolved from the cores. Annealing of the Fe@Pd core–shell particles at 800 °C led to the formation of fcc Fe-Pd solid solution. Acid treatment of the Fe-Pd alloys formed by annealing of the core–shell particles allowed selectively dissolving iron from the bcc Fe-based phase (Fe(Pd) solid solution), while the fcc Fe-rich Fe-Pd solid solution remained stable (resistant to acid corrosion). It was demonstrated that the phase composition and the Fe/Pd ratio in the alloys (phases) can be tailored by applying annealing and/or acid treatment to the as-synthesized Fe@Pd core–shell particles.

TEM Observations of the Microstructural Changes in the Interfacial Zone of Explosively Welded Titanium/Steel Before and After Ex Situ and In Situ Heat Treatment.

This paper presents the comparison of the microstructure of the interface zone formed between titanium (Ti Gr. 1) and steel (P265GH+N) in various processing stages—directly after explosive welding versus the annealing state. Transmission electron microscopy technique served as an excellent tool for studies of the sharp interface in-between the waves. Directly after the welding process in this area, a thin layer of the metastable β-Ti (Fe) solid solution was observed. In the next step, two variants of annealing have been employed: ex situ and in situ in TEM, which revealed the complete information on the interface zone transformation. The results have shown that during the annealing at 600°C for 1.5 h, the diffusion of carbon towards titanium caused the formation of titanium carbides with a layered arrangement. Compared to our previous studies, the carbides found here have a hexagonal structure. Furthermore, changes in the dislocation structure were observed, indicating the occurrence of recovery processes. Possible reasons for differences observed in the microstructure of the interface formed due to ex situ and in situ annealing are also discussed. The microstructure observations are accompanied by the microhardness measurements, which showed that the annealing caused a significant reduction in the microhardness values.

Elimination of Composition Segregation in 33Al-45Cu-22Fe (at.%) Powder by Two-Stage High-Energy Mechanical Alloying.

In the present work, complex powder alloys containing spinel as a minor phase were produced by mechanical alloying in a high-energy planetary ball mill from a 33Al–45Cu–22Fe (at.%) powder blend. These alloys show characteristics suitable for the synthesis of promising catalysts. The alloying was conducted in two stages: at the first stage, a Cu+Fe powder mixture was ball-milled for 90 min; at the second stage, Al was added, and the milling process was continued for another 24 min. The main products of mechanical alloying formed at each stage were studied using X-ray diffraction phase analysis, Mössbauer spectroscopy, transmission electron microscopy, and energy-dispersive spectroscopy. At the end of the first stage, crystalline iron was not found. The main product of the first stage was a metastable Cu(Fe) solid solution with a face-centered cubic structure. At the second stage, the Cu(Fe) solid solution transformed to Cu(Al), several Fe-containing amorphous phases, and a spinel phase. The products of the two-stage process were different from those of the single-stage mechanical alloying of the ternary elemental powder mixture; the formation of undesirable intermediate phases was avoided, which ensured excellent composition uniformity. A sequence of solid-state reactions occurring during mechanical alloying was proposed. Mesopores and a spinel phase were the features of the two-stage milled material (both are desirable for the target catalyst).

Phases and phase equilibria in the Fe–Al–Zr system

AbstractIsothermal sections at 800, 1000, and 1150 °C as well as a tentative partial liquidus surface of the ternary Fe–Al–Zr system were established by means of electron-probe microanalysis, X-ray diffraction, differential thermal analysis, and light-optical as well as scanning electron microscopy. The most prominent features of the ternary phase diagram are the extended homogeneity ranges of the Laves phases. By continuous substitution of Fe by Al, the structure changes three times starting from the cubic C15 structure of Fe2Zr to hexagonal C14 (λ1) back to cubic C15 (λ2) and again to hexagonal C14 (Al2Zr). The various Laves phase fields are separated by very small two-phase fields. Besides the Laves phases λ1and λ2, three more ternary intermetallic phases were found, whose homogeneity ranges have been determined for the first time. In addition, new results concerning the homogeneity ranges of intermetallic phases in the binary subsystems Fe–Al and Al–Zr are reported. The solubilities of the third components in the binary phases are found to be generally very low with the exception of the Laves phases. As a consequence, extended two-phase fields between the Fe(Al) solid solution and Laves phase or between Fe(Al) solid solution and the ternary ThMn12-type phase τ1are formed.

The effect of Ni and Ti additions on the glass forming ability and magnetic properties of Al-Fe-Y alloy prepared by mechanical alloying

Amorphous Al82Fe14Ni2Y2 and Al82Fe14Ti2Y2 alloys were synthesized by mechanical alloying. Morphological and structural characterizations of the powders, milled for different periods of time, were investigated by scanning electron microscopy and X-ray diffraction methods. The dissolution of Ni and Al into the Fe lattice led to the formation of Fe(Ni,Al) solid solutions in Al82Fe14Ni2Y2 alloy after 20 h of milling. A slower dissolution of Ti and Al into the Fe lattice can be observed for Al82Fe14Ti2Y2 after milling 40 h. The fully amorphous structure can be obtained for Al82Fe14Ni2Y2 after 60 h of milling. The amorphization of the Al82Fe14Ti2Y2 sample milled for 100 h was not complete, and a partially nanocrystal phase of Ti was still present. Coercivity (Hc) and the saturation magnetization (Ms) of as-milled powders decreased markedly with increasing milling time. The magnetic properties of the alloys were consistent with the structural changing during milling process. The amorphous phase transforms into fcc-Al and metallic compounds after annealed DSC treatment.

EBSD and EDX analysis at the cladding–substrate interface of a laser clad railway wheel

Abstract Electron backscatter diffraction and energy-dispersive X-ray spectrometry were used to investigate the intermixed interface produced during laser cladding of a Co – Cr –Mo alloy on a steel substrate. A multi-component system and rapid solidification conditions together lead to a complex microstructure at the interface. The solidification of the cladding starts with the formation of an interface layer, which is about 75 μm in thickness and consists of randomly oriented equiaxed grains of Co–Cr –Fe solid solution and martensite. Orientation analysis of the grains in the interface layer revealed that some grains have a special orientation relationship with the former austenite grains in the heat affected zone but the cladding is not formed by epitaxial growth on the substrate. Intermixing of the materials at the interface is providing a strong bond between the substrate and the cladding. For a grain from the interface layer to emerge as columnar grain in the cladding, it was determined that its <001> crystallographic direction is not supposed to deviate more than 25° from the sample normal direction.

Ultrafine-grained microstructure and controllable magnetic domains in Fe-based nanocrystalline alloys with excellent magnetic properties induced by hot isostatic pressing

The coarsening and inhomogeneous distribution of nano-grains caused by traditional heat treatment processes are the biggest obstacles for obtaining ultrahigh permeability and excellent comprehensive soft magnetic properties in Fe-based nanocrystalline alloys. Here, we propose a new strategy to control grain growth and magnetic anisotropy, by introducing isotropic compressive stress field in the annealing process to optimize the magnetic properties. Compared with conventional isothermal annealing, the coupling of stress-temperature field generated by hot isostatic pressing (HIP) induced the microstructure, magnetic domain evolution and magnetic properties in Si-rich Fe73.5Si15.5B7Nb3Cu1 amorphous ribbons have been systematically investigated. We demonstrate that HIP treatment promotes more Si atoms to dissolve in Fe unit cell to form Fe(Si) solid solution causing an increase in interplanar spacing. Also, the high-density Cu clusters precipitate in the amorphous matrix upon HIP serving as nucleation sites for α-Fe(Si) grains, which facilitate a high volume fraction, uniform and ultrafine-grained microstructure. Moreover, the existence of stress field introduces induced anisotropy effectively controls the magnetization mechanism and magnetic structure evolution. Furthermore, the Fe73.5Si15.5B7Nb3Cu1 nanocrystalline alloy treated by HIP exhibit excellent comprehensive magnetic properties, such as high Ms, high μe, low Pcv, low AC Hc and high Br/Bm.

Microstructure and mechanical properties of nanosecond pulsed laser welded Al–Cu–steel laminated structures

Al–Cu–steel laminated structures with configurations of Al/Cu/steel and steel/Cu/Al were obtained via nanosecond pulsed laser welding. Cavities occurred at the bottom welds in two joints. Full-penetration welds occurred more easily in steel/Cu/Al joints compared to Al/Cu/steel joints. The metallurgical reaction of Al and Fe was impeded by Cu. The eutectic (α-Al+θ) and θ-CuAl2 phases were predominant at the Al/Cu interface in the steel/Cu/Al joints, while (Cu, Fe) was the main phase in Al/Cu/steel joint. The average lap shear force of the Al/Cu/steel joints (51.2 N) was superior to that of steel/Cu/Al joints (37.2 N). The fracture for both joins occurred at the Al/Cu interface. The fracture morphologies indicated that smaller connection width and Al/Cu IMCs caused the weld pullout failure (WPF) mode in steel/Cu/Al joints. The larger connection area and presence of (Cu, Fe) solid solution were responsible for the interfacial shear failure (ISF) mode in Al/Cu/steel joints.

Structural and magnetic evolution of ball milled nanocrystalline Fe-50 at.% Al alloy

Abstract Investigations regarding structural, morphological, and magnetic changes induced by ball milling of Fe-50 at.% Al alloy have been carried out. The mechanical alloying process induces a progressive dissolution of Al into Fe, resulting in the nucleation and establishment of an elongated nanostructured Fe(Al) solid solution with the bcc structure only after 5 hr of milling. The average crystallite size of components decreased to ~5 nm and the components diffused to the nanograin boundaries during transition to nanostructured composite. Scanning electron microscopy and transmission electron microscopy confirmed the crystallite size determination and Fe(Al) solid solution formation obtained from X-ray diffraction analysis. The corresponding magnetic (Mössbauer and vibration sample magnetometer) studies confirm that there is magnetic behaviour retained in the FeAl alloys samples even after 5 hr of milling but magnetization decreases as the milling time increases. The ball milling process involves the loss of long range order and reduced grain size, which induces a transition from a paramagnetic to ferromagnetic state. The continuous refinement of grains and the antiphase interface grain bounderies play a major part in the observed variation in the magnetic properties.

Wear and Corrosion Properties of Plasma Transferred Arc Ni-based Coatings Reinforced with NbC Particles

The wear and corrosion resistance of Ni-based niobium carbide (NbC) coatings were investigated via scanning electron microscopy, energy dispersive spectrometry, particle size analysis, X-ray diffraction, electrochemical polarization, electrochemicl impedance spectroscopy, digital microhardness testing and wear testing. The results showed that the substrate was mainly composed of a γ-Cr (Fe) solid solution, and the composite coating was composed of FeNi, NbC, and Ni. In addition, the hardness of the coating increased gradually with increasing NbC content. The optimal corrosion resistance and wear resistance of the coating were realized at an NbC content of 20%.

High-temperature creep property and life prediction of aluminized AISI 321 stainless steel after annealing diffusion treatment

In this paper, pack cementation has been applied to prepare aluminized coatings on AISI 321 stainless steel. The effect of aluminizing process and subsequent annealing treatment on the creep properties and life prediction of AISI 321 was investigated at 620 °C. The results reveal that the coatings of aluminized steel are incorporated by a top inhomogeneous Al2O3, a Fe-Al intermetallic compound layer and subsequent Fe(Al) solid solution layer. In addition, the coatings thickness increased apparently after annealing. The reduction of effective bearing area due to the formation of defects around NiAl at coatings and the intrinsic brittle nature of the coating are responsible for the degradation of creep lives for aluminizing steel in comparison to that of as-received steel. During creep deformation, M23C6 and TiC precipitated at austenitic grain interior would produce dislocations radially, indicating deformation mechanism of aluminized steel domains by dislocation–dislocation interactions. However, annealed steel exhibits a discernable improved creep performance since twin boundary factions induced by annealing are as twice as before. In the creep process, tangled dislocations interact with twin boundaries, leading to the formation of weaken zones within twined region. Compared with other theories, θ-projection method has outstanding ability to predict the creep life of materials due to its adequate parameters defined to describe three typical stages of creep curve admirably.

Process control agent effect on the structural and magnetic properties of mechanically alloyed Fe(Al) disordered system

The effect of ethanol as a process control agent (PCA) on the mechanical alloying (MA) of Fe-20 at. % Al powders is presented. MA was performed at room temperature in an oscillation ball mill and its dynamic was studied by changing the milling frequency and time. We characterized the milled powders using X-ray diffraction (XRD), Mössbauer spectroscopy, and vibrating sample magnetometry (VSM). X-ray patterns for the milled powders without PCA showed a rapid formation of the disordered Fe(Al) solid solution after 25 Hz for 6 h of milling. Mössbauer spectroscopy confirmed two ferromagnetic sites related to the α-Fe phase and Fe(Al) disordered solid solution. However, intense cold welding of the powders to the milling tools for all milling frequencies led to a powder recovery of only 40% on average. The addition of ethanol as a PCA at a 25 Hz increased the powder recovery up to 96% even for different milling times, whereas X-ray diffraction and Mössbauer spectra showed a single α-Fe phase. VSM results exhibit the presence of a soft ferromagnetic character, in which a correlation between the structural parameters with the coercive field and saturation magnetization was deduced. Thus, while ethanol increases the powder recovery rate it also modifies the milling kinetics affecting the domain walls’ movement and the corresponding magnetic interactions between iron atoms.

Extremely thin interlayer of multi-element intermetallic compound between Sn-based solders and FeCoNiMn high-entropy alloy

We examined the interfacial reactions between Sn–3.0Ag–0.5Cu (SAC305) alloy/FeCoNiMn (FCNM) high-entropy alloy (HEA) and Sn–58Bi (SB58)/FCNM. FCNM exhibits a single phase with Fe, Co, Ni, and Mn solid solutions, and the FCC phase has a lattice constant of 3.601 Å, as determined by X-ray diffraction. Further, SAC305 and SB58 exhibit slightly better contact angles and spread rates on FCNM than that on Cu, which is consistent with their interfacial energies calculated by density functional theory simulations. Additionally, there is an extremely thin interlayer between SB58/FCNM (0.128 μm thickness), which is a multi-element intermetallic compound with 13.42%, 7.89%, 5.26%, 5.79%, and 67.63% (at.%) of Fe, Co, Ni, Mn, and Sn, respectively, expressed by the (Fe, Co, Ni, Mn)Sn2 intermetallic compound. The dissolution rate of FCNM into Sn was very low during the reflow process of 20 min. The findings indicate that FCNM is a promising material as a diffusion barrier between Sn-based solder/Cu solder joints with a small solder volume in a three-dimensional integrated circuit.

A binary beta titanium superalloy containing ordered-beta TiFe, alpha and omega

Alpha-beta titanium alloys excel for aeroengine applications but are typically limited to ~550°C. An alternative strategy is reinforcement with the ordered-beta TiFe intermetallic, toward ‘β-Ti superalloys’, however, there has been minimal study of TiFe precipitation in the binary system.Here, a Ti-20Fe (at.%) alloy was homogenised at 1050°C in the β-Ti phase field and aged at 600°C where the Fe supersaturation promoted TiFe precipitation. Curiously, as the TiFe volume fraction increased, the alloy hardness decreased, due to an interplay of mechanisms: (1) Fe solid solution strengthening, which reduces as the β-Ti Fe content falls to 16.2% on ageing; (2) ω precipitation strengthening, as ω-like incommensurate modulated domains were identified by transmission electron microscopy in the homogenised β-Ti parent phase and are suggested to change in size and structure after ageing, resulting in reduced ω-strengthening; (3) softening as softer TiFe and α-Ti phases precipitate from the harder ω‑strengthened β-Ti parent phase.

Mechanism of Solid-State Amorphization in the Fe-Si-Cu-Mg-O System

Solid-state amorphization process occurring at 600-1060 °C continuous annealing was observed by non-ambient x-ray diffraction on Fe-3%Si-0.5%Cu alloy surface with MgO as thermostable coating. The phenomenon was occurred at α→γ transformation temperatures (920-960 °C) in a layer consisting of Si solid solution in α-Fe and oxides (MgFe)2SiO4, (MgFe)O, SiO2. Amorphous state remained both during heating and cooling to 20 °C. Simulation for diffusion amorphization of Fe (Si) solid solution was proposed. Mg2Si complexes are reduced from oxides by hydrogen then transfer to solid solution and solid-state amorphization is occurred.

Microstructure and tensile properties of AISI 321 stainless steel with aluminizing and annealing treatment

In the present work, the tensile properties and microstructure of pack cementation preparing aluminized AISI 321 stainless steel with subsequent annealing treatment was investigated. The results reveal that the coatings of aluminized AISI 321 stainless steel are mainly composed of outermost Al2O3 layer, Fe-Al compound intermediate layer and Fe(Al,Cr) solid solution diffusion layer. The cross shape precipitate (NiAl) and strip precipitate (Ni3Al) are observed in Fe(Al,Cr) layer. After annealing, no new phase in aluminized coating is detected, meanwhile, the thickness of the aluminized coatings is increased and the porosity of Fe-Al layer is increased as well. In addition, the size of NiAl precipitates is decreased. The strength and plasticity of stainless steel are degraded by aluminizing treatment. However, after annealing, the aluminized steel exhibits a lower strength but a higher ductility. The crack initiation region of both aluminized steel with or without annealing treatment comprise coarse columnar grains and cleavage planes with river patterns. The fracture model of aluminized steel is cleavage fracture, while a mixed of intergranular and transgranular fracture is observed in aluminized annealed steel.

Synthesis and characterisation of a novel Fe-based nanocomposite by mechanical alloying and spark plasma sintering

ABSTRACT To improve low hardness and poor corrosion resistance of the Fe-based alloys, Fe–Ti–Al–B–Si–C–P–Cr novel alloy was prepared using mechanical alloying and spark plasma sintering (SPS). Two types of mills, including of high-energy planetary (HEP) and SPEX(S) ball mills (BM) were used to reach the solid solution. Mechanical alloying by the HEP route led to the formation of the Fe(α) phase after 60 h, while its milling after 15 h by high-energy SPEX mill led to the formation of the Fe(α) solid solution. After sintering of as-milled powders by SPS, the composite of Fe (α)/nanocrystalline was obtained. The micro-hardness of the HEP–SPS and the S–SPS samples obtained about 689.5 ± 0.15 and 2068.5 ± 0.18 HV0.3, respectively. The lowest corrosion current density and the highest polarization resistance were related to the HEP–SPS sample and was calculated to be 0.51 µA/cm2 and 41.668 KHz/cm2, respectively.

Effect of mechanical alloying and preheating treatment on the phase transformation of the Al–Cu–Fe compacts annealed by microwave radiation

The present study investigated the effect of mechanical alloying (MA) time, preheating and annealing process on phase and microstructural transformations in Al65Cu23Fe12 (at%) alloys. To release stresses, a part of milled powder was heated at 150 °C for 20 min and then raw compacts of the as-synthesized powders and preheated ones were prepared and heated at selected temperatures from 200 to 800 °C using microwave radiation. The results showed that with increasing the time of mechanical alloying process, the morphology of the particles changed and nanometer spherical particles were formed. Also, β-Al(Cu,Fe) solid solution phase was formed after 16 h of mechanical alloying. After 30 h of mechanical alloying, the quasi-crystalline phase did not form directly under the conditions employed in this work. Comparison of preheated samples with samples without preheating process showed that the quasi-crystal phase was formed at 300 °C for preheated samples, while the β phase was formed for samples without preheating process. The results of phase analysis also showed that β-Al(Cu,Fe) and θ-Al2Cu phases along with the quasi-crystalline phase are the main phases in the samples. The annealing process of the samples using microwave radiation leads to the formation of a quasi-crystal phase at temperatures and times much lower than other annealing methods.