Aluminum Chromium Research Articles

Hierarchical BiFeO3/Cr2CTx MXene composite as a multifunctional catalyst for hydrogen evolution reaction and as an electrode material for energy storage devices

A multifunctional hierarchical Bismuth ferrite/chromium carbide (BiFeO3/Cr2CTx) MXene has been employed as both electrode material for supercapacitors as well as an electrocatalyst for electrocatalytic water splitting. Here, a facile method is suggested for synthesizing Cr2CTx MXene from the chromium aluminum carbide (Cr2AlC) MAX Phase. X-ray diffraction studies, Scanning electron microscopy, and high-resolution transmission electron microscopy indicate that the aluminum atomic layers are removed from Cr2AlC MAX structure. The electrochemical test reveals that the BiFeO3/Cr2CTx MXene composite, which is produced with less Al2O3, performs well in the hydrogen evolution reaction (HER) with a low overpotential of 128 mV in 1 M potassium hydroxide. 53.3 mV dec−1, and 0.16 Ω cm−2, respectively, are the values of the calculated Tafel slope and charge transfer resistance. In a dielectrode electrolysis system, BiFeO3/Cr2CTx MXene electrode needs only 1.81 V of cell potential to provide 10 mA cm−2 with long-term stability. The specific capacity of 671.2 C g−1 at a current density of 1 A g−1 is obtained for BiFeO3/Cr2CTx MXene electrode with 90% capacitance retention after 3000 cycles. The potential use of BiFeO3/Cr2CTx MXene towards HER and supercapacitor application is demonstrated by this study, which offers a gentle path for the fabrication of Cr2CTx MXene composites for energy storage and HER applications.

The influence of thermal barrier coating on an LHR engine fueled by soybean biodiesel blended with various additive spectrums: Performance, combustion, and emission analysis

AbstractThe novelty of this research work deals with green synthesized nanoadditives (5% of graphene, carbon nanotubes, and carbon black), oxygenated additives (5% of n‐butanol, n‐heptane, and n‐pentanol), and then the test fuels are prepared by blending of 20% of soybean biodiesel and 70%, 80%, and 100% of premium diesel. The experimental outcomes revealed that the Nickel Chromium Aluminum (NiCrAl‐120 micron), partially stabilized zirconia, and titanium dioxide ceramic composites at about 400 microns achieve the thermal barrier coat of low heat rejection (LHR) engine parts by the air‐plasma spray method. Compared with Blend B, green synthesized carbon black (5%), premium diesel (70%), and n‐pentanol (5%) mixed soybean biodiesel (20%) fuel (Blend E) tested on the LHR engine achieved 4.90% higher brake thermal efficiency and 25.31% lower brake‐specific fuel consumption at peak load owing to the presence of an oxygenated agent (n‐pentanol) in the fuel blend, which minimizes carbon deposition. The carbon monoxide, hydrocarbon, NOx, and smoke emissions were reduced by 25.58%, 29.41%, 5.06%, and 7.75% when compared to Blend B at peak load. Then, the in‐cylinder pressure and heat release rate were found to be 4.52% and 8.87% higher for Blend E at peak load compared to Blend B. This was because the mix of oxygenated additive and carbon black bio‐based nanofuels made the combustion process go faster. These fuel blends were tested on LHR diesel engines at various load conditions.

Evaluation of the corrosion resistance of AlCoCrFeMnNi high entropy alloy hard coating applied by electro spark deposition

Although hard coatings have good resistance to wear and scratching, their corrosion resistance has decreased, failing. Improving the corrosion resistance of the hard coating has lately become a difficult subject. This work produced a newly created AlCoCrFeNiMn alloy with a high entropy using mechanical alloying and spark plasma sintering. Aluminum was added as the sixth elemental component to the chemical composition of the CoCrFrNiMn high entropy alloy to achieve this objective. Subsequently, the AlCoCrFeNiMn layer was deposited via electro-spark deposition on a substrate (ESD). To achieve a uniform layer, parameter optimization was performed, and the effects of frequency (5, 8, and 11 kHz), duty cycle (50, 60, and 70 %), and applied current (15, 25, and 35 A) were studied. Using the Vickers technique, the acquired surface microhardness of coatings was measured. The most significant measurement of hardness was around 1426 HV0.05. Using potentiostat-polarization testing and electrochemical impedance spectroscopy at room temperature, the corrosion of the coatings was evaluated. The AlCoCrFeNiMn HEA coating considerably increased the corrosion resistance of the substrate, according to the results. Corrosion rates for uncoated and coated samples were 1.44 and 0.13, respectively. At the optimal frequency of 11 kHz, the duty cycle of 60 %, and the current of 35 A, the coating exhibited the highest corrosion resistance, which was 10 times greater than the corrosion rate of the substrate. All of the coated samples displayed a passivation behavior, ascribed to the production of chromium oxide and aluminum oxide on the surface of the HEA layers due to their lower free Gibbs energy formation values. In addition, the coating's roughness was assessed, and the correlation between surface roughness and corrosion resistance was determined.

Experiments and modeling of the macroscale mechanical responses of neutron-irradiated FeCrAl alloys

Iron chromium aluminum (FeCrAl) alloys have been regarded as candidate materials for accident-tolerant fuel cladding. In this study, the stress-strain curves of various neutron-irradiated and un-irradiated FeCrAl alloys at the test temperatures of 300 K and 653 K are obtained through the uniaxial tensile tests, with the fast neutron fluences of 2 × 1019 n/cm2 and 8 × 1019 n/cm2 (E ≥ 1 MeV). Simultaneously, improved shear strain rate model and damage evolution model are proposed in the crystal plasticity theoretical frame, with the irradiation effects involved. The developed models are numerically implemented, with the simulation results of the macroscale stress-strain curves agreeing well with the experimental data. The irradiation hardening and embrittlement phenomena are captured, together with the characteristics of strain hardening and softening. The influences of alloy compositions, temperatures, and fast neutron fluences on yield strength, ultimate tensile strength, yield ratio, and uniform elongation are discussed. Macro mechanical properties such as yield strength and yield ratio are found to be near-linearly correlated with crystal plasticity model parameters. A model for multi-objective optimization of the mechanical properties is established, with which the optimum design strategies of alloy composition for the materials in the in-reactor service environments are proposed. This study could provide a theoretical basis for the research and development of advanced FeCrAl alloys.

Comparing the performance of several tool coatings in turning of commercially pure titanium grade 4

The increasing use of titanium and its alloys in the manufacture of implants results from the simultaneous presence of excellent biocompatibility, relatively low density, high mechanical properties, and corrosion resistance. Unlike the excellent application characteristics, titanium is classified as a difficult-to-machine material. Therefore, one constant challenge for implant manufacturers is to correctly choose turning tools for each application. This work aims to compare the useful life of the uncoated insert with other three types of coatings on carbide tools, titanium aluminum nitride (TiAlN), aluminum chromium nitride (AlCrN), and titanium nitride/titanium carbonitride multilayer coating (TiN + TiCN). Turning experiments were performed using grade 4 commercially pure titanium (typically used in dental implants), testing two cutting speeds for each tool used. The tests were carried out in a CNC rotary head lathe, using cutting fluid in abundance. The results showed that the uncoated insert achieved the shortest life due to its worst properties (lower surface hardness, higher friction coefficient, and lower maximum working temperature), even with its supposedly higher chemical stability with titanium. On the other hand, the tool with the TiN + TiCN multilayer coating obtained the longest tool life among the four tested inserts. The main novelty of this work is that the tool that showed the longest life (TiN + TiCN coating) did not have the best properties among the tested coatings. In fact, it had both the lowest hardness and working temperature. However, this tool has a low coefficient of friction and a multilayer structure coating, which increases its resistance against the wear mechanism that occurred predominantly in this application, which was attrition. Even with the increased cutting speed, this coating also achieved the best result. Therefore, during the machining of titanium, the most important characteristics of the tool are low coefficient of friction and resistance against the pull out of particles.

Effects of annealing temperature on the microstructure, mechanical and tribological properties of CrAlTiN coatings

The microstructure, mechanical properties and tribological properties of CrAlTiN coatings with various atmospheric annealing temperature are systematically investigated. The results show that the hardness of the coating decrease with the annealing temperature increasing from room temperature to 800 °C, however, the elastic strain resistance H/E value increase firstly and then decrease. The deposited CrAlTiN coating is face-centered cubic structure, (111) and (200) planes show competition growth, while high annealing temperature promotes the growth of (200) planes. The main wear mechanisms of CrAlTiN coating against Si3N4 ball are adhesive and oxidative. The coatings annealed at 400 °C has the lowest wear rate and annealed at 800 °C peeled off during the friction process. The chromium oxide, aluminium oxide and titanium oxide with lubricating and high hardness adhered on the wear tracks, playing the role of supporting the counterballs, a low COF of the coating is obtained. The coatings annealed above 600 °C are more easily to form extensive smooth and dense oxide adhesives, but it takes longer to reach stable wear stage. Thus, the preferred annealing temperature could effectively regulate the microstructure and improve the mechanical and tribological properties of CrAlTiN coating.

Utilization of recycled corundum as a refractory raw material: Characteristics and performance evaluation

Recycled corundum is a sustainable CaO–containing fused corundum obtained from aluminum–chromium slag. To effectively promote the application of recycled corundum, we characterized its physicochemical properties, sintering properties, and ladle slag corrosion resistance and compared them with those of white fused corundum. We also performed thermodynamic calculations to analyze the effect of CaO on recycled corundum under sintering and slag corrosion conditions. The experimental results indicated that recycled corundum has a lower thermal conductivity than white fused corundum and comparable sintering performance and better ladle slag resistance properties. The thermodynamic calculation results demonstrated that CaO promoted liquid sintering at temperatures above 1600 °C and a higher amount of CaAl4O7 formed after the ladle slag corrosion. The results of this study provided basic theoretical guidance for using recycled corundum as a substitute for white fused corundum in ladle–lining refractories.

Microstructure and corrosion behavior of Al2O3–Cr2O3 composites with various Cr2O3 content in Al2O3–SiO2–CaO–FeO slag

The corrosion of refractory materials by high-temperature slag has caused severe technical challenges and economic losses to the metallurgical industry. In this study, the microstructure and mechanical properties of Al2O3–Cr2O3 composites were investigated. The static crucible method was used to investigate the corrosion and infiltration behavior of a typical smelting reduction ironmaking slag for the Al2O3–Cr2O3 refractory. Corrosion test results indicate that the corrosion region of Cr2O3–Al2O3 composites is mainly composed of a corrosion and infiltration layer, and the thickness of the corrosion layer decreases significantly with increasing Cr2O3 content in the sample, whereas the thickness of the infiltration layer increases gradually. The dissolution of Al2O3 into the slag is the main reason for the severe erosion of Al2O3–Cr2O3 composites with a low Cr2O3 content. Increasing the amount of Cr2O3 can significantly improve the slag corrosion resistance of Cr2O3–Al2O3 composites, however will have a negative effect on the slag infiltration resistance, which is mainly owing to the increase in porosity of the composite refractory. The formation of the (Al, Cr)2O3 solid solution effectively inhibited the dissolution of alumina in the slag. In addition, excessive Cr2O3 content can also consume Al2O3 in the slag and form an (Al, Cr)2O3 solid solution, which improves the slag corrosion resistance of the aluminum chromium composite refractory.

(AlCrMg)x(PO4)y/MgO composite: A new thermal protection and insulation material up to 2400 °C

A (AlCrMg)x(PO4)y/MgO composite(APMC) was prepared based on the acid–base reaction between MgO and chromium aluminum phosphate solution for thermal protection and insulation applications at ultrahigh-temperatures up to 2400 °C. The compositions, formation mechanisms, microstructure, mechanical properties, thermal conductivity and ablation resistance of the composite were systematically investigated. The results show that the (AlCrMg)x(PO4)y/MgO composite can be consolidated in different shapes at room temperature. The compressive strength of the as-prepared porous composites is higher than 20 MPa due to the macromolecular network structure, and it can be further improved to 42 MPa via thermal treatment. After ablation by an oxyacetylene flame at 2400 ± 70 °C for 60 s, the mass and line ablation rates of the composite were 0.0195 g/s and 0.43 × 10−3 mm/s, respectively, which are comparable to those of ultrahigh-temperature ceramics. The excellent ablation resistance can be attributed to the in situ formation of a dense protective layer composed of spinel MgCr2O4 and MgO phases. Interestingly, during ablation at 2400 °C the back-side temperature of the 15 mm-thick sample was lower than 130 °C, suggesting outstanding thermal insulation performance. The temperature gradient leads to the formation of a gradated porous structure which reduces the overall thermal conductivity of the composite.

Synthesis and Characterizations of Novel Spinel Ferrites Nanocomposites Al0.5Cr0.5Zn0Fe2O4 and Zn0.5Cr0.5Al0Fe2O4

In this study, novel spinel ferrites nanocomposites containing aluminum chromium zinc nanoferrites, Al0.5Cr0.5Zn0Fe2O4 and Zn0.5Cr0.5Al0Fe2O4 have been fabricated and characterized to determine the properties of highly stable conduction materials. The nanocomposites have been synthesized through the sol–gel method. Zinc and aluminum-doped chromium ferrites were prepared with the stoichiometric composition ZnxAlx-0.5Cr0.5Fe2O4 with ammonium hydroxide solution (NH4OH) and polyethylene glycol (PEG) at different temperatures with consecutive steps. After sintering the final nanoferrites, characterizations for morphological, spectral properties, and crystallinity have been determined through scanning electron microscope (SEM), Fourier transformation infrared spectroscopy, and X-ray diffraction spectrometer, respectively. SEM micrographs presented that higher sample density and agglomeration of the nanocomposite outer surface with temperature increase. The investigation of the dielectric and conduction properties presented with varying sintering temperature and Al–Zn doping greatly influenced the dielectric properties of spinel nanoferrites dielectric properties: dielectric loss tangent and dielectric constant. The effects of various sintering temperatures provide synergistic effects on the morphology and dielectric conductivity features. The characterizations presented that the dopants (Al, Zn) enhanced the magnetic and electrical properties of both chromium nanoferrites which can be implemented in high frequency single-layered electromagnetic waves absorbing devices in electrical and medical appliances in future.

Study of the Biodegradability of Leather Tanned with Sodium Aluminosilicate

The leather industry transforms raw hides into leather by mechanical and chemical processes. The main chemical process is the tanning in which the fibers are stabilized and cannot putrefy. To this end, different chemicals can be used that are capable of forming crosslinkages between collagen molecules. In this sense, the most used products are: chromium salts, aluminum, vegetable tannins, synthetics, aldehydes, resins and silicates. In this work, a new biodegradable tanning process based on zeolites was studied in two steps. In the first one, a tanning process for sheepskins and cow hides was developed. In the second one, three types of retanning process to obtain shoe upper, vegetable and leather goods were studied. This new system allows to obtain leather that can decompose naturally in a relative short period of time. Leather tanned with this system shows similar values to the biodegradability of pure collagen.Specifically, with the retanning system used for shoe upper allows to obtain a 74.4% relative biodegradability compared to pure collagen.

Time domain and frequency domain of coated milling inserts using FFT spectrum

ABSTRACT Quality is determined by machines, materials, equipment, and lead times. The quality of aircraft materials such as aluminum and its alloys could greatly improve their applications. The difficulty of efficiently and reasonably machining certain materials limits their applicability. The purpose of this paper is to increase the quality of the vibration responses. Specifically, we examine the effects of the machining parameters on vibration (Time and Frequency domains). The end milling process is used to machine the AA6082T6 workpiece material. Speed (S), feed (F), depth of cut (DoC), and coated cutting inserts are the machining parameters. Tungsten carbide inserts (UNC), tungsten carbide inserts coated with Aluminum Chromium Nitride (AP3), and tungsten carbide inserts coated with Diamond-Like Carbon (DLC) were employed in this study. The minimum amplitude of 0.1173 g (m/s2) is seen at 710 rpm, 40 mm/min, and 0.5 mm of the DLC coated tool at a frequency of 930 Hz, according to the data. By comparing it to other cutting inserts, the DLC coated tool is given the smallest amplitude and minimum time domain. According to the findings, if the DLC coated insert is used in the machining process, the material’s surface finish will be much enhanced, and the material had good mechanical qualities.

Effect of Zr addition on coarse Laves phase stimulated nucleation of recrystallization in FeCrAl alloy

This study investigates the coarse Laves phase stimulated nucleation of recrystallization behavior in iron–chromium–aluminum (Fe–Cr–Al) alloys. The results reveal that the samples with coarse Laves phases in the matrix have finer grains because of the occurrence of particle stimulated nucleation (PSN). Due to the lower diffusion coefficient and lower solubilities of Zr in the bcc matrix, Zr addition increases the proportion of the coarse Laves phase, which promotes the PSN, resulting in a fine grain size in the Fe–Cr–Al alloys. The ultimate tensile strength of the Zr-modified Fe–Cr–Al sample with coarse Laves phases in the matrix reaches ∼600 MPa, and the elongation is up to ∼28%. Additionally, the high elongation of this sample could greatly improve its formability. The superior combination of strength and ductility is attributed to grain refinement and discontinuous deformation. This study could be expected to provide a better understanding of the coarse Laves phase, such as accelerated recrystallization behavior and beneficial effects on the mechanical properties, and provides potential freedom for further design and microstructure control of Fe–Cr–Al alloys.

Effect of MAX phase chromium aluminum carbide thin film thickness on Q-switched Erbium-doped fiber lasers

In recent years, chromium aluminum carbide (Cr2AlC) has gained attention because of its good performance in terms of high-temperature resistance, transparency and conductivity. Therefore, it has been widely used in solar cells, photonics and electronics. Although some related characteristics are investigated in pulse lasers, the effect of thin film thickness in generating laser pulses have not been reported. Therefore, the effect of thin film thickness on the performance of Q-switched erbium-doped fiber laser (EDFL) is explored in this work. Two films of different thicknesses were applied to generate Q-switched laser pulses. The thickness of the films were about 45 µm and 16 µm and they were prepared by a casting method with polyvinyl alcohol (PVA). The effects of two different film thicknesses on laser performance were investigated separately. The results show that the film thickness affects the modulation depth, saturation intensity and insertion loss of SA, which in turn effects the Q-switched laser pulses.

Urinary Metals as a Marker of Exposure in Men and Women in the Welding and Electrical Trades: A Canadian Cohort Study.

Men and women working in the welding trades undergo the same apprenticeship training but it is unknown whether, once in the trade, their exposures differ. Comparison of urinary metal concentrations, having adjusted for estimated airborne exposure, may provide an answer. Men and women were recruited to a cohort study of workers in the welding and electrical trades (the Workers Health in Apprenticeship Trades-Metal working and Electrical [WHAT-ME study]). They completed a recruitment questionnaire and further questionnaires every 6 months for up to 5 years. At each follow-up, they gave details on employment and, if welding, answered trade-specific questionnaires. Urine samples were collected by mail. Welding exposure matrices were developed to estimate metal exposures from welding process, base metal, and consumables. Urinary metal concentrations, determined by ICP-MS, were compared by trade (welding or electrical). Within welding, the relation of urinary concentrations to estimated airborne exposure was examined, with adjustment for potential confounders including sex, use of respiratory protective equipment (RPE), and time spent outdoors. Natural logarithms were taken of exposure estimates and urinary concentrations, to reduce skew. All regression analyses included creatinine concentration. Urinary metal concentrations were analysed for 12 metals in 794 samples. Antimony, arsenic, lead, and mercury had a high proportion of samples with no metal detected and were not considered further. The urinary concentrations of aluminum, cadmium, chromium, cobalt, copper, manganese, nickel, and zinc were compared for welders (434 samples) and electrical workers (360). After adjustment for potential confounders, welders had higher urinary concentrations for aluminum (β = 0.13 95%CI 0.03-0.24) and chromium (β = 0.66 95%CI 0.55-0.77). Of 434 welder urines, 334 could be matched securely to detailed information about the most recent day welding. For these, an estimate of airborne exposure was made for aluminum, chromium, manganese, and nickel. Male welders were estimated to have higher airborne exposure to chromium and nickel than women welders. No difference was seen in the estimated exposures for aluminum or manganese (or total dust). Regression analyses of the relation of urinary metals to estimated exposure showed a good concordance for aluminum (β = 0.09 95%CI 0.04-0.15 (P < 0.001) and chromium (β = 0.11 95%CI 0.05-0.17 P < 0.001). The concordance for manganese and nickel was positive, but much weaker. Urinary concentrations of aluminum and nickel were somewhat lower with increasing time wearing RPE and, for chromium and nickel, with time working outdoors. Having adjusted for estimated exposure, creatinine and other confounders, male welders had lower urine concentrations of aluminum (β = -0.35 95%CI -0.51 to -0.19 P < 0.001) chromium (β = -0.38 95%CI -0.57 to -0.19 P < 0.001) and manganese (β = -0.36 95%CI -0.49 to -0.23 P < 0.001) than female welders. Welders had higher urinary concentrations of aluminum and chromium than electrical workers. Exposure estimates of aluminum and chromium for welders were a valid representation of the airborne exposures to these metals. Although male welders were estimated to have higher exposures of chrome and nickel than female welders, the higher urinary metal concentrations in women welders is of concern, particularly for women who may conceive while in the trade.

High-temperature performance in Al2O3–Cr2O3 refractories: Effect of Al2TiO5

In an effort to reduce resource consumption through recycling, Al 2 O 3 –Cr 2 O 3 refractories were prepared by sintering a mixture of brown corundum and recycled aluminum chromium slag at 1600 °C. To elucidate the significance of TiO 2 in refractory, the effect of TiO 2 addition on the room- and high-temperature mechanical properties of these refractories was investigated. The observed stepwise progression in the high-temperature mechanical properties of the specimens was explained by considering the results of thermodynamic simulations, as well as those of phase and microstructural analyses. This behavior was ascribed to the generation of Al 2 TiO 5 in the matrix of the specimens. Moreover, the addition of TiO 2 increased the content of undecomposed Al 2 TiO 5 , and it was accompanied by the appearance of several microcracks in the matrix portion. The high temperatures caused the integration of microcracks and counteracted the thermal stresses in the specimens, which considerably improved the high-temperature mechanical properties and the thermal shock resistance.

AlCrN Coated WC by PVD at Various Deposition Temperatures

An attempt is made in this work to improve the performance and tool life of the tungsten carbide (WC) coated aluminium chromium nitride (AlCrN) via physical vapor deposition (PVD) method. Various deposition temperatures ranging from 250, 350, 400, and 450 oC were investigated to evaluate the characteristic of coated carbide. Prior to the deposition process, WC surfaces were treated in Murakami’s solution for 15 minutes followed by Caro’s solution for 10 seconds to improve the coating adhesion on WC by the dissolution of cobalt (C); roughened the carbide surface. The thickness of the coated AlCrN increases proportional with higher deposition temperatures (from 1.14 μm to 2.18 μm) and homogenously coated. While XRD analysis observed the presence of AlN and CrN phases attributed to AlCrN coating. The hardness of the coated carbide was highest at 450 oC deposition temperature (1325 HV). The qualitative scratch test following ASTM D 3363 indicated that higher temperature (400 oC and above) provides good adhesion characteristics between AlCrN coating and WC.

PVD coatings influence (TiCN, BCN, and CrAlN) on the fatigue life behavior of AISI 1045 steel for automotive applications

This work evaluated the influence of titanium carbo-nitride (TiCN), chromium aluminum nitride (CrAlN), and boron carbo-nitride (BCN) coatings deposited on AISI 1045 steel and their behavior in fatigue life. Suitable deposition parameters were established to obtain appropriate deposition times for polycrystalline growth and desired stoichiometry, as well as a stable layer thickness of ~ 3 μm. The physical and chemical properties of the obtained coatings were established by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and nanoindentation. Scanning electron microscopy (SEM) was used for analyzing the fracture surfaces of the samples subjected to fatigue. The analysis of the fatigue behavior of the uncoated and coated substrates was performed under rotary bending conditions applying maximum alternating stresses in the interval of 55 to 70% of the ultimate strength value, i.e., from 479 to 610 MPa, respectively. The test was conducted at room temperature. It was established that the fatigue resistance properties increased for the three types of coated samples, TiCN, BCN, and CrAlN, with values of 9.6%, 4.2%, and 3.9%, respectively, calculated for 1 × 106 cycles. The highest value in fatigue life improvement corresponded to the TiCN coating. This is associated with the increase in the mechanical properties of the coating, as well as the lower presence of tensile type stresses. The mechanical and fatigue results found in these ternary coatings deposited on AISI 1045 steel open up the possibility of future applications in mechanical devices, e.g., automotive applications with high fatigue demands in service conditions.

Influence of Zr on grain orientation, texture, and mechanical properties in hot- and warm-rolled FeCrAl alloys

Iron–chromium–aluminum (Fe–Cr–Al) alloys have great potential application as an accident-tolerant fuel cladding material in light-water reactors. It has excellent processing ability, resistance to steam oxidation at high temperatures (HTs), and irradiation swelling-resistance. It is necessary to improve the room- and high-temperature mechanical properties and reveal the strengthening mechanism. In this study, we analyzed the effect of Zr on the microstructure and room- and high-temperature tensile properties of hot- and warm-rolled FeCrAl alloys. The results show that the Laves phase could be effectively stabilized by Zr addition, and the proportion of low-angle grain boundaries increased. Moreover, the yield strength at room and high temperatures of the samples after Zr addition were improved, owing to the precipitation and sub-grain boundary strengthening by Zr. In addition, Zr changed the grain orientation, but had no relevance to the number of easier activated slip systems. The movable dislocation cannot slip during high-temperature tensile tests because of the pinning effect of the dynamic precipitated Laves phase, which could be the reason for the decrease in elongation at high temperatures. • Zr addition stabilized the Laves phase effectively in Fe–Cr–Al alloys. • Zr addition increased the proportion of LAGBs in hot and warm rolled Fe–Cr–Al alloys. • Zr addition did not influence the number soft orientation grains in Fe–Cr–Al alloys. • The elongation of Fe–Cr–Al alloys decreased at the high temperature tensile tests.

Determining the influence of ultra-dispersed aluminum nitride impurities on the structure and physical-mechanical properties of tool ceramics

This paper considers features related to manufacturing the chromium oxide-based tool material. The process involved ultra-dispersed powders made of aluminum nitride. It has been established that the destruction of chromium oxide at high sintering temperatures is prevented through the reaction sintering of chromium oxide (Cr2O3) and aluminum nitride (AlN). It was established that the structure of the composite depends both on the temperature and the duration of hot pressing. Thermodynamic calculations of the interaction between Cr2O3 and AlN showed that this interaction begins at a temperature of 1,300 °C. In contrast to hot pressing in the air, no СrN and Сr2N compounds were formed in a vacuum. With increasing temperature, the content of Al2O3 in solid solution becomes maximum at a temperature of 1,700 °C in the case of hot pressing in the air while in vacuum the content of Al2O3 remains unchanged within the entire temperature range of 1,300–1,700 °C. When increasing the time of hot pressing to 30 minutes, the size of individual grains reaches 10 μm. It has been shown that in the sintering process involving Cr2O3 and AlN, the plasma-chemical synthesis produces the solid solution (Cr, Al)2O3 at the interphase boundary, which improves the mechanical properties of the material. The influence exerted on the quality of the machined surface of tempered hard steel when machining by the devised tool material based on chromium oxide with an optimal admixture of 15 wt % of ultra-dispersed aluminum nitride powder was investigated. It was determined that the quality of the machined hard steel surface improved compared to standard imported tool plates. It was established that the resulting tool material, in addition to relatively high strength and crack resistance, also demonstrates high thermal conductivity, which favorably affects the quality of the machined steel surface, given that lubricants and coolants are not used during the cutting process.