Alloy Layer Research Articles

Metallic Particles‐Induced Surface Reconstruction Enabling Highly Durable Zinc Metal Anode

AbstractAqueous zinc batteries usher in a renaissance due to their intrinsic security and cost effectiveness, bespeaking vast application foreground for large‐scale energy storage system. However, uncontrolled dendrite growth along with hydrogen evolution severely restricts its reversibility and stability for practical application. Herein, the surface of Zn metal is reconstructed with metallic particles (In, Sn, In0.2Sn0.8) to diminish surface defects and regulate Zn deposition behavior. The alloyed In–Sn greatly activates the Zn surface for lower Zn adsorption energy barrier to expedite plating kinetics and confine Zn aggregation. Dense and uniform deposition of Zn on the reconstructed surface significantly prevents the Zn substrate from dendrites growth for catastrophic damage. Meanwhile, alloy layer embodies high hydrogen evolution overpotential, ensuring high plating and stripping efficiency for Zn anode. Consequently, In0.2Sn0.8 reconstructed surface realizes long‐term lifespan up to 1800 h with low polarization (12 mV) at the condition of 1 mA cm−2 and 1 mAh cm−2. When paired with sodium vanadate (NVO) cathode, the full cell steady operates for a high‐capacity retention of 94.0% after 5000 cycles at 5 A g−1. This study provides new insights into the surface‐defects dependent Zn deposition process and offers a guide for constructing stable surface for dendrite‐free Zn growth.

Formation of the Structure and Properties of the Near-Surface Layer in Alloys of the Ti–6Al–4V–H System Under Irradiation with a Pulsed Electron Beam

Formation of the Structure and Properties of the Near-Surface Layer in Alloys of the Ti–6Al–4V–H System Under Irradiation with a Pulsed Electron Beam

Method for Yttrium Alloying of the Surface Layer of Alloys

Method for Yttrium Alloying of the Surface Layer of Alloys

Study of the Mechanisms of Radiation Softening and Swelling upon Irradiation of TiTaNbV Alloys with He2+ Ions with an Energy of 40 keV.

This paper presents simulation results of the ionization losses of incident He2+ ions with an energy of 40 keV during the passage of incident ions in the near-surface layer of alloys based on TiTaNbV with a variation of alloy components. For comparison, data on the ionization losses of incident He2+ ions in pure niobium, followed by the addition of vanadium, tantalum, and titanium to the alloy in equal stoichiometric proportions, are presented. With the use of indentation methods, the dependences of the change in the strength properties of the near-surface layer of alloys were determined. It was established that the addition of Ti to the composition of the alloy leads to an increase in resistance to crack resistance under high-dose irradiation, as well as a decrease in the degree of swelling of the near-surface layer. During tests on the thermal stability of irradiated samples, it was found that swelling and degradation of the near-surface layer of pure niobium affects the rate of oxidation and subsequent degradation, while for high-entropy alloys, an increase in the number of alloy components leads to an increase in resistance to destruction.

Experimental and numerical study on the high-velocity hail impact performance of carbon fiber aluminum alloy laminates

The experiment and finite element method (FEM) simulation of high-velocity hail impact on carbon fiber reinforced aluminum alloy laminates (CARALL) were carried out in this paper. CARALL were prepared via an autoclave process after surface anodizing. The properties of the specimens were verified by mechanical properties testing. The light gas gun was employed to conduct the hail impact tests with different impact velocities, impact angles and ply sequences. The surface damage, displacement of the impact center and deformation depth in different test schemes were compared. The FEM model of the high-velocity impact of hail on CARALL was established using ABAQUS/Explicit. The strain-rate dependent model was adopted for hail while the Johnson-Cook damage constitutive model was adopted for the aluminum alloy layer. The 3D Hashin criterion damage model based on fracture energy was applied for the CFRP layer via the VUMAT subroutine. The cohesive element was inserted between the laminates to investigate the interlaminar damage. The accuracy of FEM was verified by comparing with the results obtained by tests. Combined with the energy absorption and internal damage mechanism, the effects of different parameters on the hail impact resistance of CARALL were studied.

Corrosion of galvanized steel in alkaline solution associated with sulfate and chloride ions

Corrosion mitigation strategies for structural steel bridge elements including post tensioned steel components include the use of galvanized steel. The zinc alloy layers and subsequent precipitation of a dense surface oxide in alkaline environments provide beneficial barrier protection to mitigate corrosion. However, severe corrosion of galvanized steel components in contact with sulfate-rich deficient cementitious grout was documented to occur in less than 8 years of bridge service. Electrochemical testing and material characterization showed that the presence of sulfates in alkaline solutions allow for prolonged zinc activity and hindered passivation by the incomplete surface coverage and the precipitation of large sized calcium hydroxy zincate. OCP, LPR, and electrochemical noise (EN) testing showed greater corrosion activity of galvanized steel in chloride and sulfate solutions. EN identified local corrosion activity of the zinc associated to the porous nature of the surface oxide layer.

Analysis of the kinetic growth of an electrochemically formed bronze patina using the layer‐pore resistance model

AbstractThe growth of patinas on artistic or archeological copper alloys is a determining stage to reproduce similar surface conditions such as corrosion protection of cultural heritage materials. In this work, the kinetic growth and protective properties of the corrosion products layer of a quaternary copper alloy have been characterized using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy‐EDS, atomic force microscopy, X‐ray diffraction, and Raman spectroscopy. The results of LSV show that the patina formation is a mixed process consisting of dissolution and direct film formation. EIS results show that the kinetic formation modifies the characteristics of the corrosion layer allowing a Warburg‐like diffusive mechanism or the response of a porous oxide layer without diffusive phenomena. The roughness and thickness of the patina enhance with the decrease in the scan rate. The patina is mainly composed of copper and tin corrosion products.

Study on diffusion kinetics of chromium and nickel electrochemical co-deposition in a NaCl–KCl–NaF–Cr2O3–NiO molten salt

Abstract The process of preparing surface composite by molten salt co-deposition is the result of the mass transfer of active particles in molten salt, electrochemical reduction, and solid diffusion. In this study, we prepared Cr–Ni alloy/low-carbon steel surface composites in NaCl, KCl, NaF, Cr2O3, and NiO melt salt system successfully, and analyzed the entire diffusion dynamics process, aiming to find out the limiting links and provide ideas for further improving the preparation efficiency. The results show that chromium and nickel ions are simultaneously reduced on the cathode surface through two and one steps, respectively. And an alloy layer with Fe content of 64.52 wt%, Ni content of 28.96 wt%, and Cr content of 6.52 wt% is formed on the surface of low-carbon steel substrate. The average diffusion coefficients of chromium and nickel atoms in the surface composites are 1.16 × 10−14 and 1.44 × 10−14 m2·s−1. The mass transfer process in molten salt is the limiting link in the whole preparation process.

(Invited) NiO/ β-(Al x Ga1-x )2O3 /Ga2O3 Heterojunction Lateral Rectifiers with Reverse Breakdown Voltage > 7kV

NiO/ β-(Al x Ga1-x )2O3 /Ga2O3 heterojunction lateral geometry rectifiers with diameter 50-100 µm exhibited maximum reverse breakdown voltages >7kV, showing the advantage of increasing the bandgap using the β-(Al x Ga1-x )2O3 alloy. This Si-doped alloy layer was grown by Metal Organic Chemical Vapor Deposition with an Al composition of ~21 %. On state resistances were in the range 50-2180 Ω.cm2, leading to power figures-of-merit up to 0.72 MW.cm-2. The forward turn-on voltage was in the range 2.3-2.5 V, with maximum on/off ratios >700 when switching from 5V forward to reverse biases up to -100V. Transmission line measurements showed the specific contact resistance was 0.12 Ω.cm2. The breakdown voltage is among the highest reported for any lateral geometry Ga2O3-based rectifier.

High temperature thermo-chemical properties evolution of NaF-NiF2 system

In Molten Salt Reactor (MSR), Ni based alloys are more suitable for handling of the molten fluoride salts because of formation of corrosive resistive NiF2 layer over the structural material components. A ternary mixture of LiF-NaF-KF (FLiNaK) can be used as coolant salt for transfer of heat from the reactor core. NiF2 layer of the Ni-based alloys shows reactivity towards NaF at reactor operating temperature. NaNiF3(s) is the single complex ternary compound in the NaF-NiF2 system. The compound has been synthesized and characterized. The thermodynamic stability of NaNiF3(s) has been experimentally measured in terms of Gibbs energy of formation using Galvanic cell technique and its measured ΔfG°m(T) was obtained as.ΔfG°m(T) [NaNiF3(s)]/kJ mol−1 = (−1242.9 ± 2.3) + (0.2312 ± 0.0039) × (T/K).The heat capcity and high temperature enthalpy increment was also experimentally measured using DSC and high temperature calorimetric technique, respectively and the values were obtained as.Cp,m(J·mol−1·K−1) = 117.74 + 0.0498 × T −1.07351 × 106/T2(303 ≤ T/K ≤ 828).(HT-H298)(J·mol−1) = −40270.6 + 120.4 × T + 0.0234 × T2+717669.7/T.Effect of oxygen impurity over the stability of the compound has been investigated by calculating the chemical potential diagram of Na-Ni-F-O system. The binary phase diagram of NaF-NiF2 system and the ternary phase diagram of Na-Ni-F2 system has been calculated based on Gibbs energy minimization technique using the experimental thermodynamic data.

Investigation of the regeneration of the passive surface oxide layer of TiAl6V4 alloy printed by WAAM technology using different electrochemical test methods

AbstractThe kinetics of oxide layer formation on surface of Ti6Al4V alloy samples is a very important property especially if their application as medical implants is planned. Damaged protective surface layer usually heals in ambient condition however; during the self‐healing process toxic species can get into the surrounding living tissue. In our experiment the kinetics of the healing process proceeding at 3D printed alloy surface has been studied using electrochemical methods, among them scanning electrochemical microscopy. More than 40 min. time period was found long enough for total healing.

Processes of formation of Cu–Ni alloy films by electron beam evaporation

The features of the formation of Cu–Ni alloy films by electron beam evaporation are considered. The position of the isobars of the total pressure of copper and nickel on the state diagram of the Cu–Ni during evaporation in vacuum is determined. Calculations of the elemental compositions of films have been carried out. It is shown that the nickel content in films deposited during boiling of Cu50Ni50 alloy in vacuum is 50 times less than in the alloy. The structure and elemental composition of the surface layer of alloys after their evaporation and sublimation, as well as the elemental composition of the deposited films, are investigated. It is shown that the most acceptable way to obtain films of stable composition in the Cu–Ni system is simultaneous electron beam evaporation of copper and nickel from two crucibles.

Combined effect of Ru on the oxidation behavior and microstructure stability of a single crystal superalloy

The isothermal oxidation behavior and the microstructure stability was studied at 900 °C, 1000 °C and 1100 °C of the two alloys with and without Ru. The curves of oxidation weight gain show that the oxidation resistance decreases sharply with the addition of Ru. A multi-layered scale formed on the alloy surface, and it generally consisted of an external layer of NiO, an intermediate layer of spinel and an Al2O3 inner layer. The oxidation rate at 1100 °C is significantly higher than that at the other two temperatures due to more serious cracking and peeling of oxide scale. Compared with Ru-free alloy, the oxide layer of Ru-containing alloy is thicker and the oxide layer spallation more seriously. The oxide of Ru was found in the spinel layer and the vaporization of the oxide makes the scale spallation. Surprisingly, a large number of TCP phases were found in alloy matrix, especially in 2Ru alloy. This indicates that poor oxidation resistance will lead to a decline in microstructure stability.

Evidence-based uncertainty quantification for bending properties of bimetal composites

Bimetal or laminated metal composites consisting of several metal or alloy layers can efficiently absorb the advantageous properties of each metal when utilised as raw materials for future remanufacturing. Their mechanical response characteristics and failure modes face uncertain challenges during the processing owing to the existence of heterogenous interfacial transition zones between layers. This work aims to study the uncertainty quantification in bending processing of a novel bimetal composite as a result of uncertain interfacial zones using an efficient evidence-based reliability analysis method. An analytical model for bending characteristics of bimetal composite was first established based on the deterministic material properties of each component layer, and it was employed to quantitatively analyse the bending uncertainty properties of 2205 duplex stainless steel/AH36 carbon steel bimetal composite (2205/AH36 BC) considering the epistemic uncertainty in geometric dimensions and mechanical properties of component 2205 and AH36 layers. The variation ranges of tangential stress and bending moment along the thickness direction of composite during bending process were effectively estimated, and the confidence level of each possible in the corresponding upper and lower boundaries was given for the tangential stress at each position. The analysis results illustrated that the uncertainty quantification for bending deformation properties of bimetal composite can more comprehensively understand the mechanical behaviors of composite, and provide an effective guidance for the forming fabrication of bimetal composite structure.

Nanoclusters in stacking faults in Mg-Y-Zn alloys examined by small-angle X-ray scattering and extended X-ray absorption fine structure analysis

A coarse-grained picture of segregation layers in MgYZn alloys as a two-dimensional cluster systems bound in stacking faults has been justified by a combined use of Extended X-ray absorption fine structure (EXAFS), small-angle X-ray scattering, and scanning tunneling microscopy. EXAFS analysis showed an identical relaxed atomic configuration around Y and Zn atoms as a finger print of molecular-like L12 clusters, characteristic of Long Period Stacking Ordered (LPSO) structures. The fingerprint was confirmed for wide range of compositions of cast ternary alloys containing bulk LPSO structures. The clusters in dilute MgYZn alloys, whose segregation layers were sparsely dispersed in the a-Mg matrix, showed the same fingerprint. The results suggested that the Y-Zn clusters in the segregation layers of Mg-Y-Zn alloys are identical, regardless of the cluster density in the layers or the number of segregation layers.

Field-free spin–orbit devices via heavy-metal alloy with opposite spin Hall angles for in-memory computing

With the advantages of high speed, low energy consumption, and non-volatility, spin–orbit devices are promising to be used in the field of in-memory computing. However, for large-scale integration, a simpler field-free switching scheme needs to be further explored. Here, we prepared field-free spin–orbit devices based on the PtW alloy layer with competing spin currents. The preparation of such devices is friendly to integration, because there is no requirement of introducing additional processing technology. Only the traditional heavy-metal layer is needed to be replaced by an alloy layer with opposite spin Hall angles. A series of positive and negative pulsed current tests have shown a stable field-free magnetization switching in the Ta/PtW/Co/AlOx/Pt device. The programmable Boolean logic of NAND and NOR were performed in a single device by changing the initial magnetization state. In addition, a pair of devices were connected with always opposite magnetizations to implement the XNOR logic gate, which can be applied to perform the dot product operation in the binary neural network. Based on the spin XNOR gates, a three-layer binary neural network achieves 89% recognition accuracy of handwritten digits. Our findings pave the way to efficient in-memory computing applications.

Ti-based surface alloy formed on AISI 316 L austenite steel surface using low-energy high-current electron beam

Titanium and Ti-based alloys possess good biocompatibility and excellent corrosion resistance. This paper is devoted to an effort to create Ti-based surface alloy on specimens made of the AISI 316 L austenite steel. The Ti-based surface alloy is created by the Ti film deposition using the magnetron sputtering method followed by the low-energy high-current electron beam irradiation of the Ti film–316 L steel substrate system surface. Transmission electron microscopy shows that the surface alloy consists of several sublayers having different structures and phase compositions. In particular, these are α-Ti; TiSi2; FeTi and Fe2Ti; Fe2SiTi; Fe2Ti3O9 phases and more complex Cr13Fe35Ni3Ti7, Cr12Fe32Mo7Ni7, Cr12Fe36Mo10, Mo5Cr6Fe18 phases nearby the substrate. Phase compositions of the surface alloy layers are determined by the change in the chemical composition of the titanium–steel system and the heat depth distribution. It is shown that the formation of the Ti-based surface alloy on the AISI 316 L austenite steel surface, provides the increase in the polar component of the free surface energy from 3.2% to 34.5%.

Experimental test and simulation calculation of fatigue properties of aluminum–titanium-steel explosive welded connector under tension-compression cyclic loading

The three-layer clad plate (aluminum alloy layer/commercial pure titanium layer/CCSB steel layer) was prepared by explosive welding as marine transition connector. The fatigue properties of clad plate were studied by experiment and finite element simulation. The fatigue limit and S–N curve were obtained by axial high-cycle fatigue test under tension-compression loading. The up-and-down method and group method were used respectively. Combining Static Structural module and DesignLife module based on the ANSYS Workbench Platform, the stress distribution, safety factor and fatigue life of clad plate under different loads were calculated. The results show that fatigue limit of Al–Ti-steel clad plate is 55 MPa, and the fatigue fracture mainly occurs in the 104∼106 cycles period in the stress range of 65 MPa∼100 MPa. The maximum relative error of fatigue life is 7.05%, and the relative error of fatigue limit is 0.45% between model and test fitting values. The results of finite element simulation have good agreement with the results of experimental method, which proves the feasibility and reliability of finite element simulation to analyze and forecast fatigue property of explosive welded clad plate. The position of the stress concentration is at the connection part between steel and pure titanium, while fatigue fracture occurs in the 3003 aluminum alloy layer because of the low tensile strength. Improving the tensile strength of Al-steel joint material is a key measure for solving the fracture problem of hull foundation.

Design and optimization of the bumper beam with corrugated core structure of fiber metal laminate subjected to low-velocity impact

Fiber metal laminates (FMLs) exhibit good impact resistance performance with hybrid structures based on alternating stacking of metal alloy layers and fiber-reinforced composite plies. Therefore, FMLs become excellent candidates for bumper beams in automobiles with an enhanced energy absorption capacity. Herein, the design and optimization of the bumper beam consisted of FMLs corrugated sandwich structure subjected to low-velocity impact were investigated. Firstly, material characteristic parameters of aluminum alloy and carbon fiber reinforced thermoset polymer (CFRP) were obtained from the quasi-static and dynamic experiments respectively. Then, finite element analysis (FEA) of cap structures of FMLs was established to capture the deformation process of the low-velocity impact. The simulation results were well-validated using material parameters from the dynamic mechanical tests. Afterward, the influence of material type and stacking sequences on performance was numerically investigated under low-velocity impact loading, whereas the performance of aluminum alloy and CFRP were set as controls. A multi-objective optimization method was considered to realize the maximum energy absorption with minimum impact peak force. The non-dominated sorting genetic algorithm II (NSGA-II) was introduced to obtain the global optimum solution. The current work highlights the excellent mechanical performance of the FMLs bumper beam in low-velocity impact.

Corrosion Behavior of Nitrided Layer of Ti6Al4V Titanium Alloy by Hollow Cathodic Plasma Source Nitriding.

Ti6Al4V titanium alloys, with high specific strength and good biological compatibility with the human body, are ideal materials for medical surgical implants. However, Ti6Al4V titanium alloys are prone to corrosion in the human environment, which affects the service life of implants and harms human health. In this work, hollow cathode plasm source nitriding (HCPSN) was used to generate nitrided layers on the surfaces of Ti6Al4V titanium alloys to improve their corrosion resistance. Ti6Al4V titanium alloys were nitrided in NH3 at 510 °C for 0, 1, 2, and 4 h. The microstructure and phase composition of the Ti-N nitriding layer was characterized by high-resolution transmission electron microscopy, atomic force microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. This modified layer was identified to be composed of TiN, Ti2N, and α-Ti (N) phase. To study the corrosion properties of different phases, the nitriding 4 h samples were mechanically ground and polished to obtain the various surfaces of Ti2N and α-Ti (N) phases. The potentiodynamic polarization and electrochemical impedance measurements were conducted in Hank's solution to characterize the corrosion resistance of Ti-N nitriding layers in the human environment. The relationship between corrosion resistance and the microstructure of the Ti-N nitriding layer was discussed. The new Ti-N nitriding layer that can improve corrosion resistance provides a broader prospect for applying Ti6Al4V titanium alloy in the medical field.