Alloy Layer Research Articles

Synchrotron XPS and Electrochemical Study of Aging Effect on Passive Film of Ni Alloys

To investigate aging effect on the passive film of Ni23Cr15Mo and Ni22Cr9Mo3Nb, synchrotron-based X-ray photoelectron spectroscopy (XPS) was used to analyze the structure and composition of the air-formed passive film on the alloys. The corrosion resistance of the two Ni alloys in 1 M NaCl solution was evaluated with electrochemical cyclic polarization measurement. The synchrotron XPS measurement provided detailed information about chemical states of alloying elements in the passive film, showing that the passive film consists of an inner oxide layer and an outer hydroxide layer. The XPS data allowed precise determination of the chemical composition and the thickness of the outer hydroxide layer, the inner oxide layer, and the underlying subsurface alloy layer. The Cr-oxide in the inner layer grows thicker with aging time, leading to Cr-depletion in the subsurface region. Mo and Nb in the alloy form mixed oxides and hydroxides, and aging in air leads to transformation of the lower valence oxides into higher valence oxides. The freshly formed oxide film exhibits similar barrier properties as the aged oxide film. The stability of the passive film formed on Ni22Cr9Mo3Nb seems to be better than that on Ni23Cr15Mo.

Surface Characteristic and Friction Behavior of Plasma Sprayed FeCoNiCrMo0.2 High Entropy Alloy Coatings on BS960 High-Strength Steel with Subsequent Shot Peening Treatment

The FeCoNiCrMo0.2 high entropy alloy coatings were deposited on BS960 high strength steel by plasma spraying method with four different current intensities (250 A, 350 A, 450 A, 550 A). These coatings were then subjected to a subsequent micro-shot peening treatment. Surface characteristics including surface morphology, microhardness and phase composition were characterized, and the wear resistance of the coatings was assessed by reciprocal friction and wear tests. The results showed that the high entropy alloy coatings had FCC structure. XRD results showed that no new phase was formed during the spraying process. At the same time, shot peening treatment could effectively improve the hardness of the coating surface. Under the four processes, the coating surface prepared with the current intensity of 350 A had the highest microhardness and uniformity before and after shot peening, and the hardness values were 473 ± 10.21 and 504 ± 8.62 HV0.2, respectively. The friction and wear test results showed that the friction coefficients of the four coatings were close to each other at 10 N load, which was about 0.4. When the test load reached 25 N, the friction coefficient of the coating with current intensity of 350 A was lower, and it showed better friction performance. After shot peening, the friction coefficient of the four coatings further decreased to about 0.3 under 10 N loading due to the existence of hardened surface layer. When the test load reached 25 N, the hardened layer would be worn through and the friction coefficient would suddenly rise. Under the 25 N test load, the hardened layer of the high-entropy alloy coating with current intensity of 350 A illustrated better friction resistance.

Induction brazing of NdFeB magnet with PVD-deposited AgCu alloy

The NdFeB magnets service in high-power electric-mechanical conversion devices sometimes endure high stress and high-temperature impact, and adhesion of these magnets using glue cannot ensure the reliability. In this study, the NdFeB was induction brazed with physical vapor deposition (PVD)-deposited Ag72Cu28 alloy layer, then the microstructure, mechanical properties and magnetic properties of the brazed joints were characterized, and effects of the filler metal thickness and the induction heating time were analyzed. The results show that the PVD coating can effectively prevent the surface oxidation of the NdFeB. The AgCu filler metal penetrates into the NdFeB and is partly mixed with the liquefied Nd-rich intergranular phase of the NdFeB, forming a good metallurgical bonding. The thickness of the penetration layer increases obviously with increase of the heating time and filler metal thickness. The bonding strength of the NdFeB brazed joint increases firstly and then decreases with increasing heating time, and a peak bending strength of 196.94 MPa was obtained. Fracture of the brazed joint occurs inside the NdFeB substrate close to the penetration layer. After a further annealing, the coercivity of the brazed NdFeB sample is a little higher than that of the un-brazed sample, and the squareness decreases by only a little. Properties of the brazed joints might be further improved by optimizing the amount of filler metal and the induction heating parameters.

High-Performance Anodes Made of Metallic Lithium Layers and Lithiated Silicon Layers Prepared by Vacuum Technologies

Replacing conventional electrode materials is one of the most pressing challenges for next-generation lithium-ion batteries since state-of-the-art systems have almost reached their limitations for performance gains. For anodes, ambitious candidates include lithium and silicon because of their extremely high capacity. In this paper, a physical vapor deposition process for the preparation of pure metallic lithium layers and lithiated silicon layers in the layer thickness range of 1–20 µm is demonstrated. The lithium layers were deposited by thermal evaporation. Static coating rates up to 120 nm/s and dynamic deposition rates up to 1 µm·m/min were realized. Furthermore, the deposition of lithiated silicon alloy layers with various compositions was performed via the co-evaporation of lithium and silicon, where silicon was evaporated by an electron beam. The process was characterized regarding the deposition rate, heat loads, and effects of substrate pre-treatment. To achieve a porous microstructure, the layer morphology needed to be manipulated by adapting process parameters. Stripping experiments revealed high electrochemical activity of the lithium up to 85 %. The innovative approach carried out via vacuum processing showed capabilities for overcoming the current bottlenecks experienced with high-capacity anode materials in combination with the potential for upscaling to high throughput production.

Advanced fuel and burnable absorbers designed for long-cycle operation of BNPP

The present study is based on the facts that are happening for the Bushehr Nuclear Power Plant (BNPP) and coincides with the operational changes and step-by-step modifications of the BNPP in the near future. Bushehr reactor core will change from BNPP core to TVS-2M core. In other words, a new fuel, called the TVS-2M, is being used by the Russians to upgrade WWER-1000 reactors to reduce power generation costs, increase cycle length and fuel consumption. The neutronic analysis performed in this work is in line with this change. It provides a feasibility study of BA change and increase of cycle length in BNPP reactor without changing the initial structure of the reactor core. This research provides a new core configuration that can achieve the stated goals to a large extent without changing the BNPP core to the TVS-2M core. This research provides a feasibility study of Integrated burnable absorber (IBA) change by maintaining the initial neutronic conditions and a new high-performance configuration aiming for a long-cycle operation in Iran's nuclear power reactor. In Water-Water Energetic Reactors (WWER) reactors, two alternatives to CrB2Al (current burnable absorber in BNPP) are gadolinia (Gd2O3-UO2), and erbia (Er2O3-UO2). The benefits of the combinational IBA concept are expected by compensating weak points of each other. The main contribution of this research is the use of two cylindrical coaxial IBA layers with the same volume of gadolinium pins plus erbium (separated by a thin layer of zirconium alloy (Zr + 1% Nb)) and gadolinium pins. A neutronic evaluation has been conducted to investigate the variations of effective multiplication factor versus burnup, reactivity swing, power peaking distribution, moderator temperature coefficient (MTC), critical boron concentration (CBC), and cycle length. The result shows that the cycle length can be extended from 296 days in the BNPP core to 366 days in the proposed core, which is comparable to the cycle length of the TVS-2M core. The average BA concentration in the proposed core is 5%, which is lower than the average BA concentration of 5%–8% in the TVS-2M core. Regarding the gain of 73.90 days in cycle length, the revenue is estimated to be around 19,503,000 USD, making it worth the implementation considering the number of gadolinium and erbium pins in the proposed core.

Microstructure of aluminium alloy welding under an external magnetic field

In this paper, the effect of alternating longitudinal electromagnetic fields on the microstructure, composition segregation and solid solubility of solute elements in aluminium alloy weld beads is studied. The results show that the X-ray diffraction peaks of the deposited aluminium alloy layer under the external magnetic field are much less intense than those for the alloy prepared without the external magnetic field. The diffraction peak intensities from different crystallographic planes in the structure slightly differ under the action of different magnetic field frequencies. As the excitation current increases, the increase in Mg segregation is obvious. With an increase in the magnetic field frequency and excitation current, the external magnetic field promotes the solid solubility of solute Mg in Al.

Effect of temperature on anti-corrosion properties of aluminum alloy anodized by sulphuric acid

Temperature is one of the most important parameters in anodizing treatments of aluminum alloys as it directly affects the quality of the anodic coatings. This research study has examined and investigated the effect of this important parameter on the anti-corrosion properties of the anodizing layers of aluminum alloy 5083.The morphology and crystalline structure of anodic oxide layers were characterized respectively by X-ray diffraction, scanning lectron microscopy and EDX analysis. The corrosion behaviour of the alloy, before and after anodization at different temperatures, was analyzed in chlorinated medium using different electrochemical techniques, namely open circuit potential measurement, potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that temperature has a significant influence on the quality of the anodic oxide layers. Therefore, for a relatively low treatment temperature, the developed anodic films show high surface roughness values and contain fewer pores and defects compared to the films obtained at 20°C. Electrochemical analysis indicates that these films also show good corrosion resistance in the chloride environment. This is reflected by relatively low corrosion current density values as well as relatively high polarization resistance values.

Micro- and macro-scale characterization of the microstructure and scratch resistance of the 5083-anodic aluminum oxide film

This paper focuses on the thickness, microstructural, and scratch resistance of the sulfuric oxide layer of 5083-aluminum alloy for different anodizing durations/reaction times (RT = 30, 60, and 90 min). The thickness and the microstructure analyses were carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and ImageJ post-processing software. The scratch resistance was investigated using macro- and micro-scratch tests. Experimental results revealed that the oxide layer was covered by larger-sized microcavities and a thicker oxide layer for 90 min RT. Moreover, the area, which was covered by microcavities percentage, was decreased for 60 min RT and increased for 90 min RT. Besides, using the macro-scratch test, and when increasing RT, no micro-cracks were detected inside the scratch mark. Nerveless, the increasing of the normal load was shown that the oxide layer was more resistant to scratch. Finally, the 5083-aluminum alloy oxide layer had a high-scratch resistance such as a weak penetration depth and a low friction coefficient.

Sb and O dual doping of Chlorine-rich lithium argyrodite to improve air stability and lithium compatibility for all-solid-state batteries

Chlorine-rich lithium argyrodites with ultrahigh ionic conductivity show great potential as solid electrolytes in all-solid-state batteries, while the poor moisture and lithium metal compatibility limit their applications. Here, by tailoring Sb and O dual dopant, Li5.5P0.96Sb0.04S4.40O0.10Cl1.5 electrolyte delivers a high Li-ion conductivity up to 7.20 mS cm−1, excellent air/moisture and lithium metal endurance. The improved air stability is due to the strong Sb–S and P–O bonds in the co-doped electrolyte, inhibiting the reaction with water. While the enhanced lithium metal stability is attributed to the formation of the Li–Sb alloy layer, impeding the growth of lithium dendrites during cycling. The lithium symmetric cell using Li5.5P0.96Sb0.04S4.40O0.10Cl1.5 exhibits high critical current density (1.5 mA cm−2) and ultralong cyclability (750 h, 0.1 mA cm−2). The all-solid-state lithium metal battery using LiNi0.6Mn0.2Co0.2O2 cathode affords a high initial discharge capacity of 144.2 mAh g−1 at 0.1C. Moreover, the assembled battery shows a discharge capacity of 116.2 mAh g−1 at 0.5C and a capacity retention rate of 83.2% after 200 cycles. This work provides the guideline to design sulfide solid electrolytes that enable all-solid-state lithium metal batteries with high energy density and long cyclability.

Study on wear properties of 7075 aluminum alloy by laser alloying imitating shell surface structure with different unit spacing

Based on observation of shell surface structures of wear-resistant organisms in the nature, Al–Ni "soft-hard interphase" nonsmooth bionic "shell" surface were prepared by adding alloy element Ni into the surface of 7075 Al alloy through laser alloying. Thereby, the wear resistance of 7075 Al alloy materials was significantly improved.By laser alloying and adding alloying element Ni to the surface of 7075 aluminum alloy, the "soft and hard alternating" non smooth bionic surface with different Al Ni unit spacing were prepared. Therefore, the wear resistance of 7075 aluminum alloy material is significantly improved.When the unit spacing was 3 mm, the wear resistance of bionic samples was optimized. In comparison with the untreated samples, the weight loss due to wear declined by 82.14% in the treated samples. Moreover, the stress distribution in the wear process of bionic samples was simulated by ABAQUS finite element simulation software. Together with the microstructure and phase changes of alloyed layers, the wear resistance mechanism of bionic alloyed samples was further analyzed.

Microstructure and Properties of Laser Cladding AlxFeCoCrNiMn High Entropy Alloy of Q345 Steel

High entropy alloy is a multi-component alloy material with equal or near atomic number, which has excellent wear resistance and corrosion resistance. In this paper, AlxFeCoCrNiMn (x = 0,0.5,1.0,1.5) high entropy alloy cladding layer was prepared by laser cladding on Q345 steel plate. The phase structure, microstructure, hardness and wear resistance of the cladding layer were studied. The results show that the cladding layer of AlxFeCoCrNiMn alloy has good metallurgical bonding ability with Q345 steel. The cladding area is mainly columnar and equiaxed. The cladding layer of AlxFeCoCrNiMn alloy is mainly composed of BCC + FCC solid solution phase, which is caused by the addition of Al element under the high entropy effect. Al element promotes the formation of BCC phase structure. With the increase of Al element, the hardness of cladding layer increases. The hardness of A1.0 cladding layer is 670HV, which is close to three times of Q345 steel. When Al (x = 1.0), the hardness of the cladding layer is the highest, and it also shows better wear resistance with lower friction and wear loss.

Термическая стабильность структурно-фазового состояния алюминия и сплавов системы Al – Si, легированных атомами циркония при воздействии компрессионных плазменных потоков

The results of structural-phase state investigations of Аl, Al – 12,6 wt. % Si – 0,1 wt. % Fe and Al – 12,6 wt. % Si – 0,5 wt. % Cu – 2,7 wt. % Mg – 0,3 wt. % Ni – 0,3 wt. % Fe – 0,2 wt. % Mn alloys surface layers alloyed by zirconium atoms under action of compression plasma flows are presented. The formation of metastable compounds Al3Zr with L12 structure and (Al,Si)3Zr with D022 structure in the alloyed layers of aluminum and silumin samples, respectively, was found. Alloying with zirconium atoms makes it possible to increase the microhardness of surface layer in 1.4 – 3 times. Thermal stability of the structure and phase composition of alloyed layers at 550 °C was investigated. The transformation of Al3Zr – L12 into Al3Zr – D023 phase in aluminium and (Al,Si)3Zr disintegration with ZrSi2 in Al – Si alloys was observed during annealing. The formed surface layers had elevated temperature strength.

Defect Formation in Aluminum-coated Steel by Heat Treatment

A carbon tool steel plate was coated with an aluminum foil with a thickness of 100 μm by explosive welding. This aluminum-coated steel was heat-treated in the temperature range of 973−1273 K for up to 3.6 ks in the atmosphere to form a Fe-Al alloy layer on the steel surface. The alloy layer was basically composed of Fe2Al5, two kinds of FeAl (Al-rich FeAl and Fe-rich FeAl), Fe3Al containing carbon (Fe3Al(C)) and ferrite stabilized by aluminum diffusion (α-Fe(Al)). FeAl2 was also detected together with Fe2Al5 at more than 1223 K. At 1273 K, island-shaped Fe3Al(C) was produced in α-Fe(Al), and the Fe-rich FeAl/α-Fe(Al) interface became indistinct. In addition, defects like a crack and a void were observed in the vicinity of Fe-rich FeAl. The purpose of the present study is to investigate the reason for the defect formation. Various heat treatments were conducted for the aluminum-coated steel, and it was found that a temperature-rising step was responsible for the defect formation. This consideration got support from the results of two-step heat treatment, which was a heating process at 1273 K immediately after holding for 600 s near the eutectoid temperature in the Fe-C binary system.

Spin-orbit torque efficiency improved by BiSePt alloy

In order to achieve high-efficiency spin-orbit torque devices, higher charge-spin conversion efficiency, and lower resistivity are required in the strong spin-orbit coupling layer that provides the spin current. In this work we prepare BiSePt alloy/Co heterostructures with in-plane magnetic anisotropy by magnetron sputtering deposition. The alloy layer is deposited via one of two procedures, either co-sputtering or alternative-sputtering. We study the BiSePt alloy samples and find that the spin orbit torque (SOT) efficiency decreases with the increase of Pt component, which is attributed to the change of topological order of Bi<sub>2</sub>Se<sub>3</sub> amorphous surface, caused by Pt doping. And the resistivity decreases with the increase of Pt component, which depends on the increase of metallic property. Due to the balance of these two competing mechanisms, the spin Hall conductivity of the alloy layer varies non-monotonically with the concentration ratio, and reach an optimal value at a ratio of 67% of Bi<sub>2</sub>Se<sub>3</sub> component. With the increase of the Bi<sub>2</sub>Se<sub>3</sub> component, the SOT efficiency, electrical resistivity and spin Hall conductance of the alloy layer show different trends. At about 20%–70%, they increase/decrease tardily. At about 70%–100%, the resistivity ascends more prominently than the SOT efficiency, which leads the spin Hall conductance to decrease. Comparing with using the co-sputtering deposition, the electrical conductivity and spin Hall angle of the alloy layer obtained using alternating sputtering deposition are small, which is attributed to the enhancing of interfacial scattering and the filter effect of Pt on the spin flow. In contrast to traditional pure heavy metal materials (such as Pt, Ta) and topological insulator materials like Bi<sub>2</sub>Se<sub>3</sub>, our BiSePt alloy devices obtained by co-sputtering deposition achieve industry-matched preparation conditions, greater SOT efficiency, and considerable electrical conductivity of the alloy layer, thus making further applications of SOT devices possible.

Spatially isolating Li+ reduction from Li deposition via a Li22Sn5 alloy protective layer for advanced Li metal anodes.

A Li alloy based artificial coating layer can improve the cyclic performance of Li metal anodes. However, the protective mechanism is not well clarified due to multiple components of the artificial layer and complicated interface in liquid electrolytes. Herein, a single-component Li22Sn5 alloy layer buffered Li anode is paired with a solid-state polymer electrolyte, where a metallic Sn film is sputtered onto the Li anode and the subsequent alloying reaction leads to the formation of a Li22Sn5 phase. During the striping/plating process, the thickness and composition of the Li-Sn alloy passivation layer remain unchanged. Meanwhile, Li+ ions are reduced on the top surface of the Li22Sn5 layer, then the reduced Li atoms immediately pass through the alloy layer, and finally dense Li deposition occurs beneath the protective layer, realizing spatial isolation of the electrochemical reduction of Li+ from Li nucleation/growth. This unique protection mechanism can principally avoid the formation of Li dendrites and efficiently mitigate irreversible reactions between the Li anode and the polymer electrolyte. The synergistic effects lead to a clean and flat surface of the protected Li electrode, enabling a prolonged cycle lifetime over 1300 h at 25 °C at 0.1 mA cm-2 and 0.1 mA h cm-2 in a configuration of symmetrical cells.

Anomalous critical supercurrent and half-integer Shapiro steps based on Josephson junction of topological insulator nanowires

Topological insulator-based Josephson junction, as a candidate device for searching for Majorana zero energy modes, has attracted much attention. One of the key issues along this direction is to fabricate Josephson junctions with high-quality interfaces, hoping to searching for 4π-period current-phase relation in topologically non-trivial Josephson junction. In this work, the Josephson junctions based on three-dimensional topological insulator nanowires Bi<sub>2</sub>Te<sub>3</sub> and Bi<sub>2</sub>(Se<sub><i>x</i></sub>Te<sub>1–<i>x</i></sub>)<sub>3</sub> are fabricated to study their superconducting proximity effects, multiple Andreev reflections, and current-phase relations. A number of interesting phenomena are observed, including the anomalous enhancement in junctions’ critical supercurrent with magnetic field, and the appearance of half-integer Shapiro steps in the ac Josephson effect. And, we discuss the possible origins of the observed anomalous behaviors in general, and their relation with the ferromagnetic layer of TiTe alloy formed at the interface between the topological insulator nanowires and the Ti buffer layer of the metallic electrodes, in particular. We provide the experimental evidence for the formation of a ferromagnetic TiTe alloy layer at the interface of our device. And, we believe that the formation of such a layer in our Josephson device breaks the time reversal symmetry, leading to the observed anomalous enhancement of the critical supercurrent with magnetic field, as well as the appearance of half-integer Shapiro steps. Our results suggest that to study the topologically non-trivial behaviors such as 4π-period current-phase relation, one still needs to improve the interface quality of the superconductor-normal metal-superconductor type of Josephson junction devices.

PROPERTIES OF THE COMBINED COATING FOR THE RESTORATION OF WORN CYLINDER LINERS

The service life of the cylinder liner of an internal combustion engine after repair caused by wear of the internal working surface has a shorter service life than a new one. This circumstance necessitates the search for a method of applying a more wear-resistant coating. The possibility of using a combined coating to restore worn cylinder liners by applying a layer of aluminum alloy by cold gas-dynamic spraying followed by micro-arc oxidation of the working surface was investigated. (Research purpose) The research purpose is increasing the life of cylinder liners by applying a combined coating using cold gas-dynamic spraying and micro-arc oxidation of the inner working surface of the cylinders. (Materials and methods) Conducted studies on the adhesive and cohesive strength of the coating and comparative tribological tests to determine the suitability of the coating under study for the repair of cylinder liners. We performed studies according to the standards of OST 90148-74 and GOST 23.224-86, respectively. (Results and discussion) The values of adhesive and cohesive strength were determined for various modes of coating with cold gas-dynamic spraying on a cast-iron base. The optimal loading parameters for accelerated wear resistance tests were identified and the run-in rate, the factor and the wear intensity for the studied and reference coatings were calculated. It was established that the adhesive and cohesive strength is sufficient for the application of this method in practice, the wear resistance of the coated sample exceeds the wear resistance of the reference sample. (Conclusions) The combined coating has sufficient strength indicators and high wear resistance indicators compared to the standard, which makes their use in cylinder liners possible and appropriate, however, further investigation of the coating properties is necessary.

Влияние режимов лазерного ударного упрочнения на физико-механические свойства поверхностного слоя алюминиевого сплава Д16

The effect of laser shock peening modes on the physical and mechanical properties of the surface layer of the D16 aluminum alloy was investigated. Experiments were carried out with different values of laser radiation intensity and with fixed values. The dependences of the maximum deformations and microhardness in the center of the spot on the radiation intensity are obtained. The effect of increasing the laser radiation energy on the plasma expansion process is investigated. As a result, “critical points”were found, after which the nature of the dependences of microhardness and maximum deformations on the intensity of laser radiation changes. It is also concluded that the application of the Fabbro model to simulate the process of laser shock peening with the available assumptions is unreliable

A liquid metal-fluoropolymer artificial protective film enables robust lithium metal batteries at sub-zero temperatures.

Batteries that are both high-energy-density and durable at sub-zero temperatures are highly desirable for deep space and subsea exploration and military defense applications. Our design incorporates a casting membrane technology to prepare a gallium indium liquid metal (LM)/fluoropolymer hybrid protective film on a lithium metal anode. The LM not only spontaneously forms a passivation alloy layer with lithium but also reduces the nucleation potential barrier and homogenizes the Li+ flux on the surface of the lithium anode. The fluoropolymer's polar functional groups (-C-F-) effectively induce targeted dispersion of gallium indium seeds, and the unique pit structure on the surface provides oriented sites for lithium plating. By implementing these strategies optimally, the protected lithium metal anode remains in operation at a current density of 20 mA cm-2 with an over-potential of about 50.4 mV after 500 h, and the full cells have a high capacity retention rate of up to 98.5% at a current density of 0.5 C after 100 cycles. Furthermore, the battery shows improved low temperature performance at -30 °C, validating the potential of the protective film to enable battery operation at sub-zero temperatures.

Microstructure and wear analysis of CoWC alloy layers deposited by PTA process

CoWC composite coatings were produced on AISI 430 steel by the plasma transfer arc cladding. Three different powder mixtures containing WC (90%, 85% and 80%) and Co (10%, 15% and 20%) were used. Phase composition, microstructural characterization and coating properties were investigated by using scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), elemental mapping, hardness and wear test. The wear shape morphology of coatings was determined by SEM. The increased ratio of WC in CoWC powders reduced the degradation of CoWC. The substrate hardness of 180 HV gained a coating hardness value of approximately 462 HV. An increase in the hardness of the coating alloy compared to the substrate was achieved. W2C, WC, CoC and Co6W6C phases were determined on the coating surface. The high levels of WC concentration on the coating surface increased the wear resistance.