Search

Mg2(Fe, Cr, Ni)HX synthesis was successfully performed using magnesium hydride and 316L austenitic stainless steel. It was proven that despite being widely used and considered inert, under some conditions, this steel could react with magnesium hydride and be used as a reaction substrate for complex hydride synthesis. The properties of the product are different from those of pure Mg2FeH6, which suggests the partial substitution of iron atoms with chromium and nickel. The influence of milling time on hydrogen content and phase composition was studied and compared to the reference material. It was found to be likely that mechanically induced martensite formed in austenitic stainless steel during ball milling may enable the reaction between steel and magnesium hydride.

Two different methods of rapid manufacturing—electron beam additive manufacturing (EBAM) and laser-engineered net shaping (LENS)—were used in order to fabricate NiTi elements. Microstructure and martensitic transformation temperatures of initial materials in the form of wire or spherical powder were established. The samples fabricated using LENS technique showed martensitic transformation temperature (MTT) at − 26 °C (represented by maximum martensite peak maximum in DSC) which was lower in comparison with raw powder. In the case of samples fabricated using EBAM, the MMT reached − 19 °C. The peaks of martensite and reverse transformations were diffuse due to differences in grain size and composition across the sample. Aging at 500 °C for 2 h caused not only separation of R-phase during cooling of both samples, but also formation of sharper and higher transformation peaks as well as shift of MTT to higher temperatures. Microstructural investigation showed columnar grains, near the interface of deposited element and base plate, growing perpendicular to the plate surface. The grains showed axial fiber texture along the growth direction. STEM micrographs revealed the presence of elongated particles enriched in Ti. Formation of Ti-rich particles during the process led to the depletion of Ti in the matrix and contributed to increase in MTT in comparison with initial NiTi powder. LENS-deposited sample additionally contained higher dislocation density in the austenite. Compression stress/strain curves of EBAM-deposited sample revealed deformation of martensite only, while the LENS-deposited one showed almost complete superelastic effect in compression mode up to 3%.

Annealing undoped MgB2 wires under high isostatic pressure (HIP) increases transport critical current density (Jtc) by 10% at 4.2 K in range magnetic fields from 4 T to 12 T and significantly increases Jtc by 25% in range magnetic fields from 2 T to 4 T and does not increase Jtc above 4 T at 20 K. Further research shows that a large amount of 10% SiC admixture and thermal treatment under a high isostatic pressure of 1 GPa significantly increases the Jtc by 40% at 4.2 K in magnetic fields above 6 T and reduces Jtc by one order at 20 K in MgB2 wires. Additionally, our research showed that heat treatment under high isostatic pressure is more evident in wires with smaller diameters, as it greatly increases the density of MgB2 material and the number of connections between grains compared to MgB2 wires with larger diameters, but only during the Mg solid-state reaction. In addition, our study indicates that smaller wire diameters and high isostatic pressure do not lead to a higher density of MgB2 material and more connections between grains during the liquid-state Mg reaction.

This research was funded by the Institute of Low Temperature and Structure Research, PAS, the Institute of High Pressure Physics, PAS and Ministry of National Defense Republic of Poland Program-Research Grant MUT Project 13-995. The wire samples of this work were fabricated with financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) research project with grant numbers 217 M665. Our results show that a lower density of unreacted Mg + B material during an Mg solid-state synthesis reaction leads to a significant reduction in the quantity of the superconducting phase and lowers the homogeneity of the superconducting material. It also significantly reduces the irreversible magnetic field (B-irr), critical temperature (T-c), upper magnetic field (B-c2), engineered critical current density (J(ec)), and n-value, despite high isostatic pressure (HIP) treatment and the use of nanoboron in the sample. Our measurements show that samples with large boron grains with an 8% higher density of unreacted Mg + B material allow better critical parameters to be achieved. Studies have shown that the density of unreacted material has little effect on B-irr, T-c, B-c2, J(ec), and the n-value for an Mg liquid-state synthesis reaction. The results show that the critical parameters during an Mg liquid-state synthesis reaction depend mainly on grain size. Nanoboron grains allow for the highest B-irr, T-c, B-c2, J(ec), and n-values. Scanning electron microscopy (SEM) images taken from the longitudinal sections of the wires show that the samples annealed under low isostatic pressure have a highly heterogeneous structure. High isostatic pressure heat treatment greatly improves the homogeneity of MgB2. Institute of Low Temperature and Structure Research, PAS; Ministry of National Defense Republic of Poland Program-Research Grant MUT Project [13-995]; Scientific and Technological Research Council of Turkey (TUBITAK) research project [217 M665]; Institute of High Pressure Physics, PAS

A high-purity copper foil was passivated in aqueous solution of 1.0 M NaOH at −200 mV at room temperature. Top-view micrographs were taken after 30, 90, 150 and 600 s of passivation. Nanowires with a diameter of up to 56 nm, consisting of Cu2O and CuO were obtained. The mechanism of the nanowires growth was investigated based on the current density–time curves, relevant micrographs and morphology analyses. It was found that the nuclei is formed at electrolyte-electrode interface, leading to the formation of the first bunches of nanowires. Then, nanowires grow by the expansion and decomposition of the formed oxide bunches in the electrolyte, which can be understood through the current density – time curves.

The paper presents a methodology investigation of honeycomb cellular structures deformation process in quasi-static compression tests. Two honeycomb topologies with different elementary cells were designed and manufactured from Ti-6Al-4 V alloy powder with the use of Laser Engineered Net Shaping (LENS) system and compressed using a universal strength machine. To simulate the deformation process with LS-Dyna software, the mechanical properties of the material were assessed and correlated. An elasto-visco-plastic material model (Mat_Plasticity_With_Damage) was used for predicting the material behavior. The results of experimental tests and numerical simulations were compared. A reasonable agreement between deformation, failure and force histories was obtained. Additionally, both the topologies were compared for their energy absorption capabilities. The validated numerical modelling with the adopted constitutive model will be used in the further studies to analyze different cellular structures topologies subjected to dynamic loading.

Magnesium hydride, despite the decomposition temperature being incompatible with the operating temperature of a typical PEM cell, is still considered a prospective material for hydrogen storage. Hence, this paper presents new aspects of the influence of milling time on the structural changes and temperature of MgH2 decomposition, with particular emphasis on the changes taking place in the first few seconds of the milling process. This paper presents qualitative and quantitative changes in the powder particle morphology determined using scanning electron microscopy (SEM) and infrared particle size analysis (IPS) systems. The crystallographic structure of the powders in the initial state and after mechanical milling was characterized by X-ray diffraction. The decomposition temperature and activation energy were determined by the differential scanning calorimetry (DSC). Changes in the activation energy and decomposition temperature were observed after only 1&ndash, 2 min of the milling process. Two basic stages of the milling process were distinguished that impacted the MgH2 decomposition temperature, i.e., mechanical activation and a nanostructuring process. The activation was associated with the initial stage of particle size reduction and an increase in the fraction of fresh chemically active powder particle surfaces. On the other hand, the nanostructuring process was related to an additional decrease in the MgH2 decomposition temperature.

The effect of Nb content on microstructure, mechanical properties and superelasticity was investigated for a series of Ti-xNb alloys, fabricated by the laser engineered net shaping method, using elemental Ti and Nb powders. The microstructure of as-deposited materials consisted of columnar &beta, phase grains, elongated in the built direction. However, due to the presence of undissolved Nb particles during the deposition process, an additional heat treatment was necessary. The observed changes in mechanical properties were explained in relation to the phase constituents and deformation mechanisms. Due to the elevated oxygen content in the investigated materials (2 at.%), the specific deformation mechanisms were observed at lower Nb content in comparison to the conventionally fabricated materials. This made it possible to conclude that oxygen increases the stability of the &beta, phase in &beta, &ndash, Ti alloys. For the first time, superelasticity was observed in Ti&ndash, Nb-based alloys fabricated by the additive manufacturing method. The highest recoverable strain of 3% was observed in Ti&ndash, 19Nb alloy as a result of high elasticity and reverse martensitic transformation stress-induced during the loading.

In this work an assessment of the susceptibility of the AE44 magnesium alloy to stress corrosion cracking in a 0.1M Na2SO4 environment is presented. The basic assumed criterion for assessing the alloy behavior under complex mechanical and corrosive loads is deterioration in mechanical properties (elongation, reduction in area, tensile strength and time to failure). The AE44 magnesium alloy was subjected to the slow strain rate test (SSR) in air and in a corrosive environment under open circuit potential (OCP) conditions. In each variant, the content of hydrogen in the alloy was determined. The obtained fractures were subjected to a quantitative evaluation by original fractography methods. It was found that under stress corrosion cracking (SCC) conditions and in the presence of hydrogen the mechanical properties of AE44 deteriorated. The change in the mechanical properties under SCC conditions in a corrosive environment was accompanied by the presence of numerous cracks, both on fracture surfaces and in the alloy microstructure. The developed method for the quantitative evaluation of cracks on the fracture surface turned out to be a more sensitive method, enabling the assessment of the susceptibility of AE44 under complex mechanical and corrosive loads in comparison with deterioration in mechanical properties. Mechanical tests showed a decrease in properties after SSRT tests in corrosive environments (UTS &asymp, 153 MPa, &epsilon, = 11.2%, Z = 4.0%) compared to the properties after air tests (UTS &asymp, 166 MPa, &epsilon, = 11.9%, Z = 7.8%) but it was not as visible as the results of quantitative assessment of cracks at fractures (number of cracks, length of cracks): after tests in corrosive environment (900, 21.3 &mu, m), after tests in air (141, 34.5 &mu, m). These results indicate that the proposed new proprietary test methodology can be used to quantify the SSC phenomenon in cases of slight changes in mechanical properties after SSRT tests in a corrosive environment in relation to the test results in air.

Porous TiAl3 intermetallics were synthesized by the thermal explosion (TE) reaction from TiH2–75 at.% Al elemental powders combining with carbamide as the space holder. The results showed that the space holder particles were removed completely by dissolving in water before sintering and the violent exothermic reaction occurred from the temperature of 672–1193 °C within a few seconds. After TE, TiAl3 was the dominant phase in sintered products and the open porosity of 60.8% was obtained without space holder, while the porosity considerably increased to 81.4% with the addition of 60 vol% carbamide particles. The pore-forming mechanism can be concluded as follows: the sphere large pores replicated from carbamide particles and the small pores generated by the TE reaction. Moreover, porous TiAl3 intermetallics possess the excellent oxidation resistance at 650 °C in air, which enabled them good candidate materials for improving the service life and the accuracy of filtration under special conditions.

Nanoporous oxide was formed by self-organized two-step anodizing of FeAl intermetallic alloy in 0.3 M (COOH) 2 with 20 vol% of glycol, what allowed to decrease ionic mobility and consequently decrease current density and oxide growth rate. Additionally, the voltage range for anodizing was extended up to 40 V, while compared to FeAl anodizing in sulfuric acid. Furthermore, morphology of the grown oxide can be controlled by the voltage: pore diameter and interpore distance increase linearly with the voltage, but slopes of the fitted lines are smaller than in the case of intermetallics anodizing in different electrolytes.

Our research show that the higher packing density of the unreacted material (Mg +2B) by 8%, especially for Mg in the solid state, allows to eliminate the large number of large voids (20 mu m), improves the homogeneity and density of the MgB2 superconducting material, allows to obtain a greater number and longer lengths of connections between MgB2 grains, eliminates the formation of the intermetallic phase (iron borides), allows to obtain MgB2 grains of a uniform size and shape, increase irreversible magnetic field (Birr), critical temperature (T-c) and upper magnetic field (B-c2). Research show that spherical grains significantly reduce the number of inter-grain connections in the material with low and high density of unreacted material and allows to obtain the more superconducting phase. Research shows that MgB2 grains with a plate-like and rectangular shape allow to obtain more connections between the grains. Studies show that thermal treatment under high iso-static pressure does not allow to obtain the large amount of superconducting phase for the unreacted material of low density. Moreover, studies show that the high packing density of unreacted material and thermal treatment under high isostatic pressures (0.8 GPa and 1.1 GPa) allow to obtain a large amount of superconducting phase even for Mg in the solid state. Additionally, studies points that heat treatment under medium isostatic pressure (0.3 GPa) significantly reduce B-irr and B-c2. Our results are important for long superconducting wires made by using the powder-in-tube (PIT) technique. Because they indicate that the higher packing density of the unreacted material (Mg +2B) will allow to obtain a the superconducting material with greater homogeneity and density, and improve the critical parameters e.g. coils. (C) 2021 Elsevier B.V. All rights reserved.

This paper investigates the effect of multiwalled carbon nanotubes on the mechanical and electrical properties of epoxy resins and epoxy composites. The research concerns multiwalled carbon nanotubes obtained by catalytic chemical vapor deposition, subjected to purification processes and covalent functionalization by depositing functional groups on their surfaces. The study included the analysis of the change in DC resistivity, tensile strength, strain, and Young’s modulus with the addition of carbon nanotubes in the range of 0 to 2.5 wt.%. The effect of agents intended to increase the affinity of the nanomaterial to the polymer on the aforementioned properties was also investigated. The addition of functionalized multiwalled carbon nanotubes allowed us to obtain electrically conductive materials. For all materials, the percolation threshold was obtained with 1% addition of multiwalled carbon nanotubes, and filling the polymer with a higher content of carbon nanotubes increased its conductivity. The use of carbon nanotubes as polymer reinforcement allows higher values of tensile strength and a higher strain percentage to be achieved. In contrast, Young’s modulus values did not increase significantly, and higher nanofiller percentages resulted in a drastic decrease in the values of the abovementioned properties.

Multicomponent high entropy alloys based on LaNi5 phase are investigated as hydrogen storage materials. The multicomponent La Ni Fe V Mn alloys are produced from pre-alloyed and elemental gas-atomized powders using Laser Engineered Net Shaping (LENS) technology. The effect of the alloy chemical composition on the hydrogen storage properties are elucidated in terms of the structure, phase composition and alloy formation entropies. The results of phase analysis indicates that laser manufactured alloys possess primary two-phase structure that changes from σ + La(Ni,Mn)5 to FCC + La(Ni,Mn)5 alloys. Maximum hydrogen capacity of La Ni Fe V Mn alloys is proportional to the atomic content of lanthanum which is able to form CaCu5-type La(Ni,Mn)5 phase. Produced alloys show differential behavior while forming the hydride phase and no simple relationship between phase compositions and pressure-composition curves can be observed.

A composite rod, designed for the neutron absorption in nuclear research reactors or Nuclear Power Plants (NPPs), was synthesized by ball milling and subsequent Hot Isostatic Pressing (HIP-ing), similarly to the one reported in Ref. [3]. Its core consists of the oxide dispersion strengthened ferritic Fe-Cr matrix and 40 wt.% of TiB 2 reinforcement, surrounded by a Ti tubing/cladding with a functionally graded interface layer. The Specific Surface Area (SSA) for the ball-milled pre-alloyed powders increases from 0.64 to 2.92 m 2 /g and XRD shows that the crystallite/grain size of TiB 2 is ∼38 nm. Berkovich nanoindentation study after irradiation with 160 keV He + ions at a fluence up to 1 × 10 17 He + /cm 2 shows an initial hardening effect at fluences of 1 × 10 15 and 1 × 10 16 ions/cm 2 . Hardness and elastic modulus of the Fe-Cr -TiB 2 core rapidly drops when the fluence reaches 1 × 10 17 ions/cm 2 . The Ti cladding seems to be relatively impervious to increased radiation fluence since its hardness and elastic modulus change very slightly with increasing ion fluence. The observed changes in the mechanical properties are discussed in terms of vacancy/dislocation loops and He bubble formation in the irradiated microstructure. Although the He-vacancy complexes are widely regarded as being immobile, it is hypothesized here, based on the grazing incidence XRD (GI XRD), that interstitial helium diffuses outward through the boundaries of the (100) hcp-TiB 2 nanograins. As a result, the relaxation of compressive strains due to high concentration of vacancies in a nanograin crystalline lattice finally leads to the hcp-TiB 2 unit cell contraction.

In the current work, porous anodic alumina (PAA) thin films have been fabricated from doped aluminum films, Al-1 wt% Si, using a one-step anodization method at room temperature. Two different electrolytes, namely, oxalic and phosphoric acids, have been utilized to obtain the PAA. A Fast Fourier transform based arrangement analysis for the obtained nanopores is reported. It is found that the nanoporous oxide layer is formed in Al-1 wt% Si with poor arrangement due to the poor spatial distribution of the nanopores, although they are in perfect circular shape. Moreover, the transient curves during the anodization, pore density, pore diameter, and interpore distance have been investigated.

Nanostructured anodic oxide layers on an FeAl3 intermetallic alloy were prepared by two-step anodization in 20 wt% H2SO4 at 0 &deg, C. The voltage range was 10.0&ndash, 22.5 V with a step of 2.5 V. The structural and morphological characterizations of the received anodic oxide layers were performed by field emission scanning electron microscopy (FE-SEM). Therefore, the formed anodic oxide was found to be highly porous with a high surface area, as indicated by the FE-SEM studies. It has been shown that the morphology of fabricated nanoporous oxide layers is strongly affected by the anodization potential. The oxide growth rate first increased slowly (from 0.010 &mu, m/s for 10 V to 0.02 &mu, m/s for 15 V) and then very rapidly (from 0.04 &mu, m/s for 17.5 V up to 0.13 &mu, m/s for 22.5 V). The same trend was observed for the change in the oxide thickness. Moreover, for all investigated anodizing voltages, the structural features of the anodic oxide layers, such as the pore diameter and interpore distance, increased with increasing anodizing potential. The obtained anodic oxide layer was identified as a crystalline FeAl2O4, Fe2O3 and Al2O3 oxide mixture.

Nanostructured anodic oxide layers on an FeAl3 intermetallic alloy were prepared by two-step anodization in 20 wt.% H2SO4 at 0°C. The voltage range was 10.0 – 22.5 V with a step of 2.5 V. The structural and morphological characterizations of the received anodic oxide layers were performed by FE-SEM. Therefore, the formed anodic oxide was found to be highly porous with a high surface area, as indicated by the FE-SEM studies. It has been shown that the morphology of fabricated nanoporous oxide layers is strongly affected by the anodization potential. The oxide growth rate first increased slowly (from 0.010 μm/s for 10 V to 0.02 μm/s for 15 V) and then very rapidly (from 0.04 μm/s for 17.5 V up to 0.13 μm/s for 22.5 V). The same trend was observed for the change in the oxide thickness. Moreover, for all investigated anodizing voltages, the structural features of the anodic oxide layers, such as the pore diameter and interpore distance, increase with increasing anodizing potential. The obtained anodic oxide layer was identified as a crystalline FeAl2O4, Fe2O3 and Al2O3 oxide mixture.

In this article, the significant impact of a lamellar (layered) structure and a high isostatic pressure on the normal state resistance (R-n), critical temperature (T-c), irreversible magnetic field (B-irr), upper magnetic field (B-c2) and critical current densities (J(c)) at 4.2 K and 20 K was presented. Our research showed that annealing at temperatures in the range of 630 degrees C-680 degrees C (above the melting point of Mg) at atmospheric pressure (0.1 MPa) did not create a lamellar (layered) structure. This led to low T-c, J(c) and B-irr, and high R-n. The analysis, made by using scanning electron microscopy (SEM), showed that the annealing temperature increased up to 700 degrees C under a pressure of 0.1 MPa, which created a lamellar structure. This led to significant growth of T-c, J(c) and B-irr and a slight increase of R-n. Moreover, the measurements showed that annealing at temperatures from 630 degrees C to 700 degrees C did not change the B-c2 value. In comparison to pressureless heat treatment, annealing under the high isostatic pressure of 1.1 GPa obtained a lamellar structure with layers of lower thickness and higher density. This led to significant increases in J(c) and B-irr and a visible reduction of R-n. SEM analysis showed that the increase of isostatic pressure up to 0.3 GPa created a lamellar structure with thicker layers and lower density. This microstructure led to lower J(c) and B-irr and significantly higher R-n. On the other hand, the SEM analysis showed that annealing under 0.8 GPa did not cause the formation of a layered structure, and as a result, it led to significant reductions in B-irr and J(c) (4.2 K and 20 K) and higher R-n. The increase of the isostatic pressure from 0.1 MPa to 1.1 GPa did not affect T-c (B = 0 T) and B-c2. The results indicated that the layered structure obtained a high density of pinning centers, which were particularly effective at higher magnetic fields. J(c) of 100 A/mm(2) in 8 T at 4.2 K was obtained in in situ undoped MgB2 wires after annealing at 700 degrees C for 40 min under an isostatic pressure of 1.1 GPa. (C) 2018 Elsevier B.V. All rights reserved.

Tri-axial plane-strain forging was applied to the Fe–28Al–5Cr–0.8Zr–0.04B intermetallic alloy, in order to study its grain refinement and possible improvement in mechanical properties. The forging temperature range was from 20 to 600 °C. The maximum number of forging passes was 67. The deformed microstructure was investigated using electron backscatter diffraction in a scanning electron microscope. At forging temperatures

The mechanical properties and corrosion resistance of 316 L stainless steel fabricated using the Laser Engineered Net Shaping (LENS) technique have been studied. The crack-free, full density samples made using SS316L alloy powder and the LENS technique are characterized by an unusual distinct dual-phase microstructure. STEM analysis revealed a significant increase of Cr and Mo content and a decrease of Ni in the grain boundaries. Based on the Cr and Ni content (austenite stabilizing elements), the Schaeffler diagram and the EBSD results, the existence of intercellular delta ferrite on subgrain boundaries and austenite in the fine-grains are observed. The XRD patterns, in addition to the FCC austenite phase, revealed the second BCC ferrite phase. Moreover, the sigma (FeCr) phases are present in the analyzed 316 L stainless steel. The occurrence of ferrite, which does not occur in regular stainless steel fabricated using conventional metallurgical methods, improves the mechanical and corrosion properties of the LENS-fabricated sample made using 316 L stainless steel powder. The obtained results prove that the microstructure of the SS316L fabricated using LENS is heterogeneous; its impact on the mechanical properties is visible. The analyzed samples are characterized by anisotropic mechanical properties that are favorable. For both the perpendicular and parallel directions of tensile tests, samples had a ductile fracture with many dimples inside of the larger dimples. The corrosion potential of SS316L LENS and classically manufactured steel is similar. The SS316L fabricated using LENS is characterized by a relatively low value of corrosion current density, which translates into much smaller corrosion rates.

The Fe–Cr–Ti-Nb elemental powders were mechanically alloyed/ball milled with TiB2 and a small quantity of Y2O3 ceramic to synthesize a novel Fe-based alloy-ceramic powder composite that could be processed by hot isostatic pressing (HIP) for a perceived potential application as a neutron absorber in nuclear reactors. After ball milling for the 30–80 h duration relatively uniform powders with micrometric sizes were produced. With increasing milling time a fraction of TiB2 particles became covered with the much softer Fe-based alloy which resulted in the formation of a characteristic “core-mantel” structure. For the final HIP-ing process the mechanically alloyed powders were initially uniaxially pressed into rod-shaped compacts and then cold isostatically pressed (CIP-ed). Subsequently, the rod-shaped compacts were placed in the Ti-tubing and subjected to hot isostatic pressing (HIP) at 1150 °C/200 MPa pressure. The HIP-ing process resulted in the formation of the near-Ti and intermediate diffusional layers in the microstructure of HIP-ed samples which formed in accord with the Fe-Ti binary phase diagram. Those layers contain the phases such as α-Ti (HCP), the FeTi intermetallic and their hypo-eutectoid mixtures. In addition, needle-like particles were formed in both layers in accord with the Ti-B binary phase diagram. Nanohardness testing, using a Berkovich type diamond tip, shows that the nanohardness in the intermediate layer areas, corresponding to the composition of the hypo-eutectoid mixture of Ti-FeTi, equals 980.0 (±27.1) HV and correspondingly 1176.9 (±47.6) HV for the FeTi phase. The nanohardness in the sample's center in the areas with the fine mixture of Fe-based alloy and small TiB2 particles equals 1048.3 (±201.8) HV. The average microhardness of samples HIP-ed from powders milled for 30 and 80 h is 588 HV and 733 HV, respectively.

Using a two-step self-organizing anodization of FeAl intermetallic alloy in sulfuric acid, a mixed nanoporous anodic aluminum-iron oxide composite with a voltage-controlled morphology and bandgap was obtained. The chemical composition of nanoporous oxide composites formed with Al, Fe and O elements was determined by X-ray photoelectron spectroscopy. It was demonstrated that bandgap of the resulting anodic oxide composites can be tuned from 3.65 eV (samples prepared at 5 V) to 2.06 eV (samples prepared at 17.5 V), which was attributed to the increase in the composition ratio of the oxyhydroxide MOOH (where M = Al and Fe). Thus, water is more involved in the formation of oxide MOOH. After annealing at 600 °C, X-ray diffraction confirmed formation of a spinel phase of FeAl 2 O 4 . FE-SEM observations of the formed oxide demonstrated that ultra-small nanopores with a diameter of 12.8 ± 3.0 nm were formed at 5 V. The pore diameter and interpore distance were found to be linearly dependent on the voltage; however, slopes of the fitted curves were much larger than that of nanoporous anodic oxide formed on aluminum. Large current densities recorded during anodization allowed for formation of nanoporous anodic oxide with a growth rate of up to 743.0 ± 17.9 μm/h (20 V).

FeAl intermetallic alloy was anodized in 20 wt% sulfuric acid at 0 °C for 1 min at the voltage ranging from 5 to 20 V with a step of 2.5 V. Based on the FE-SEM images, fast Fourier transformed (2D-FFT) quantitative arrangement analysis of the porous oxide was performed for the oxide formed after the first and the second step of anodization. It was found that for voltages below 15 V FFT-derived regularity ratio values for both steps are comparable. For 15 V and greater voltages regularity ratio of the obtained anodic oxide is much better while a two-step procedure is employed. Conducted research revealed that two-step self-organized anodization improves regularity of the porous oxide formed on FeAl intermetallic alloy. Moreover, regularity ratio increases rapidly with the anodizing voltage for the second step of anodization.

The microstructure and mechanical properties of the Fe 3 Al–0.35Zr–0.1B alloy fabricated by the Laser Engineered Net Shaping (LENS) technique are presented. Proper technological parameters of the LENS manufacturing process were selected to obtain elements with a minimal porosity and a satisfactory shape congruency. The Fe 3 Al based alloy samples fabricated by the LENS technique are characterized by a homogenous chemical composition and diversified grain morphology with columnar grains at the bottom and equiaxed grains at the center and edge in the analyzed sample. Phase analysis showed the presence of B2 ordered Fe 3 Al intermetallic and (Fe, Al) 2 Zr Laves phases. An isothermal annealing carried out at 450 °C for 50 h led to a phase transformation from a B2 to an equilibrium D0 3 phase. The Fe 3 Al based alloy samples with the B2 structure, directly after the LENS process and with the D0 3 structure after annealing, exhibited similar yield strength and ultimate tensile strength. However, the presence of the D0 3 structure caused a noticeable increase of elongation, especially at elevated temperatures.