Alloy Layer Research Articles

Obtaining a high-nickel-alloyed layer on the surface of low-carbon steel using monometallic powders and laser processing

The paper studies deposition of a highly nickel-alloyed corrosion-resistant layer on the surface of a low-carbon economically alloyed steel. The formation of the layer is carried out in two stages – at the first stage, a precursor coating is applied by cold spraying, and at the second, an alloyed layer is formed on the surface by laser. A layer with a nickel content of up to 70% is formed on the surface of the steel. The results of X-ray diffraction phase analysis indicate that a face-centered cubic lattice of a solid solution and Ni3Fe intermetallic compound has been formed in the studied layer.

Iterative Machine Learning-Aided Framework Bridges Between Fatigue and Creep Damages in Solder Interconnections

Costly and time-consuming approaches for solder joint lifetime estimation in electronic systems along with the limited availability and incoherency of data challenge the reliability considerations to be among the primary design criteria of electronic devices. In this article, an iterative machine learning framework is designed to predict the useful lifetime of the solder joint using a set of self-healing data that reinforce the machine learning predictive model with thermal loading specifications, material properties, and geometry of the solder joint. The self-healing dataset is iteratively injected through a correlation-driven neural network (CDNN) to fulfill the data diversity. Outcomes show a very significant enhancement in lifetime prediction accuracy of the solder joint within a very short time. The effects of solder alloy and solder layer geometry are separately evaluated on the creep-fatigue damage evolution of the solder joint. The results reveal that Sn–Ag–Cu-based solder alloy generally has a better performance. Moreover, the creep and fatigue damage evolutions are found dominant, respectively, in Sn–Pb- and Sn–Ag–Cu-based solder alloys. The proposed framework offers a tool allowing for the reliability-driven design of electronic devices in the early stage of fabrication.

Microstructure analysis of martensite stainless steel by directed energy deposition and uniform high hardness

This investigation focuses on obtaining martensite stainless steel part with uniform mechanical properties along the building direction (BD) by plasma arc direct energy deposition (DED). A tailored 1Cr17Ni2B alloy powder and layer minimum temperature control process were employed. The results revealed that the tensile strengths along BD exhibited a good uniformity with a relative difference less than 1.4 % and the average ultimate tensile strength was 1382 MPa. The high microhardness along the BD also showed a good uniformity, only slightly fluctuated from 542–606 HV0.3 with a periodic length of one concave fish-scale pattern. Then the part along BD was simplified to overlapped concave fish-scale patterns. The microstructure evolution of fish-scale pattern was studied and the result showed that the concave fish-scale pattern was characterized by intragranular lath martensite and intergranular M23(C,B)6+α-Fe eutectic structure. Besides, M2(C,B) particles were distributed on intergranular α-Fe matrix. The layer minimum temperature control of 200︒C process was employed to ensure the eutectic M23(C,B)6 in a concave fish-scale pattern only partly dissolved during the deposition of the next one layer, not during the subsequent layers. It is helpful to deposite concave fish-scale patterns along the BD with similar volume fraction of eutectic M23(C,B)6 and mechanical properties. This investigation discloses a new method to deposite Fe-Cr-C-B alloy part containing intergranular carbides with uniform mechanical properties and high hardness along the BD.

Polymer interdigitated pillar electrostatic (PIPE) actuators

This work reports a three-dimensional polymer interdigitated pillar electrostatic actuator that can produce force densities 5–10× higher than those of biological muscles. The theory of operation, scaling, and stability is investigated using analytical and FEM models. The actuator consists of two high-density arrays of interdigitated pillars that work against a restoring force generated by an integrated flexure spring. The actuator architecture enables linear actuation with higher displacements and pull-in free actuation to prevent the in-use stiction associated with other electrostatic actuators. The pillars and springs are 3D printed together in the same structure. The pillars are coated with a gold–palladium alloy layer to form conductive electrodes. The space between the pillars is filled with liquid dielectrics for higher breakdown voltages and larger electrostatic forces due to the increase in the dielectric constant. We demonstrated a prototype actuator that produced a maximum work density of 54.6 µJ/cc and an electrical-to-mechanical energy coupling factor of 32% when actuated at 4000 V. The device was operated for more than 100,000 cycles with no degradation in displacements. The flexible polymer body was robust, allowing the actuator to operate even after high mechanical force impact, which was demonstrated by operation after drop tests. As it is scaled further, the reported actuator will enable soft and flexible muscle-like actuators that can be stacked in series and parallel to scale the resulting forces. This work paves the way for high-energy density actuators for microrobotic applications.

Separation mechanism of a Si+TiSi2 eutectic alloy and metal impurity Fe segregation via electromagnetic directional solidification of Ti-80 wt%Si alloy melt

The separation mechanism of Si+TiSi2 eutectic alloy and Fe atom segregation were investigated during the electromagnetic directional solidification of Ti-80 wt%Si alloy melt at pull-down rates from 5 µm/s to 20 µm/s. The experimental results indicated that a fine lamellar Si+TiSi2 eutectic alloy was obtained in the middle of the ingot after electromagnetic directional solidification. Fe impurities were captured by primary SiC particles at the bottom of the ingot, which then segregated at the top of the ingot. When the pull-down rate was 5 µm/s, the solidification front was always close to the induction coil. Electromagnetic stirring produced forced convection that promoted Si+TiSi2 eutectic alloy precipitation by mixing the melt and offsetting the temperature gradient caused by the precipitation of the primary phase, thereby inhibiting segregation. Thus, the optimal pull-down rate for fabricating Si+TiSi2 eutectic alloy was 5 µm/s. At this pull-down rate, the maximum thickness of the Si+TiSi2 eutectic alloy layer was 27 mm, and the removal rate of impurity Fe in this layer reached 98.98%.

HAADF STEM and Ab Initio Calculations Investigation of Anatase TiO2/LaAlO3 Heterointerface

The understanding of the origin of a two-dimensional electron gas (2DEG) at the surface of anatase TiO2 remains a challenging issue. In particular, in TiO2 ultra-thin films, it is extremely difficult to distinguish intrinsic effects, due to the physics of the TiO2, from extrinsic effects, such as those arising from structural defects, dislocations, and the presence of competing phases at the film/substrate interface. It is, therefore, mandatory to unambiguously ascertain the structure of the TiO2/substrate interface. In this work, by combining high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), density functional theory calculations, and multislice image simulations, we have investigated the nature of strainless anatase TiO2 thin films grown on LaAlO3 substrate. In particular, the presence of oxygen vacancies in anatase TiO2 has been proved to stabilize the formation of an extra alloy layer, Ti2AlO4, by means of interface rearrangement. Our results, therefore, elucidate why the growth of anatase TiO2 directly on LaAlO3 substrate has required the deposition of a TiOx extra-layer to have a 2DEG established, thus confirming the absence of a critical thickness for the TiO2 to stabilize a 2DEG at its surface. These findings provide fundamental insights on the underlying formation mechanism of the 2DEG in TiO2/LAO hetero-interfaces to engineer the 2DEG formation in anatase TiO2 for tailored applications.

Tribological behaviors of HfC coating prepared on 45 steel via double glow plasma surface metallurgy technique

Purpose45 steel is a common material for the manufacture of various components such as shafts or gears. However, its poor surface properties often limit its applications. The purpose of this paper is to find a way to enhance the surface performance of 45 steel, which is expected to improve the wear resistance of 45 steel.Design/methodology/approachDouble glow plasma surface metallurgy technique was used to prepare hafnium carbide (HfC) coatings on the surface of the 45 steel with two preparation process; one is to diffuse two elements together, while the other is to diffuse step by step. The scanning electronic microscopy and the X-ray diffraction were used to analyze the morphology and phase of the HfC coatings. And then the wear tests were carried out for this coating.FindingsCoating diffused step by step shows better performance; it has a 15-µm alloyed layer which is uniform and dense and its hardness can reach up to 1326.5 Vickers-hardness (HV). While the coating fabricated by diffusing elements together owns a 10-µm alloyed layer and its hardness is 1204.1 HV. According to the wear test results, both coatings have a protective effect on the substrate and the coating prepared by step-by-step diffusion process has less wear volume, indicating that it possesses better friction reduction.Originality/valueA new method which diffuses elements together was successfully used to prepare compound HfC coating, which can reduce the cost of coating preparation and improve the efficiency of coating preparation.

Improving the Corrosion Resistance of Magnesium Alloy AZ31 by a Duplex Anodized and Sol-Gel Coating

Abstract Magnesium and its alloys have found application in several areas viz., aerospace, electronics industry, and automobile, owing to their specific strength-to-weight ratio, thermal conductivity, electromagnetic shielding, etc. However, poor corrosion resistance limits their applicability for widespread use. Anodization and micro arc oxidation (MAO) are commonly used to enhance the corrosion protection of magnesium alloys. The anodized or MAO layers are porous, and hence, organic sealants are conventionally used for sealing the pores. There are not many reports on the use of organic-inorganic hybrid coatings as sealants on anodized layers of magnesium alloys. In this study, the hybrid sol-gel silica-based coatings were investigated as sealants on anodized magnesium alloy AZ31 substrates. A thick (∼20 µm) and porous oxide layer was deposited by anodization using sodium silicate as electrolyte. Ambient curable hybrid silica coatings with and without corrosion inhibitors like cerium oxide and 8-hydroxyquinoline were deposited by dip coating method. The anodized layer and the duplex coating were analyzed using X-ray diffraction and field emission scanning electron microscopy with energy-dispersive X-ray analysis (EDAX) attachment. Electrochemical impedance spectroscopy and potentiodynamic polarization studies were used to assess the corrosion protection performance of these coatings in 0.61M NaCl solution. The porous anodized magnesium oxide layer improved the binding strength of the adjacent sol-gel layer; the sol-gel layer physically sealed the porous anodized coating and offered higher corrosion protection. The duplex coating prevented the diffusion of aggressive ions onto the magnesium alloy AZ31 and enhanced the corrosion resistance significantly.

Study on oxidation behavior of Al-Mg-Sc alloy

The high temperature oxidation behavior of Al-Mg-Sc alloy has been investigated. The structure and composition of oxide layer of Al-Mg-Sc alloy were analyzed by SEM, XRD and ARXPS. The microstructure evolution of Al substrate near the interface between Al-Mg-Sc alloy and oxide layer was explored by EBSD. The results showed that the oxide layer was mainly composed of MgO and small amounts of MgAl2O4. The formation of MgAl2O4, which was mainly distributed at the bottom of the oxide layer, was followed by formation of MgO. The phenomenon of grain boundary wetting by the second solid phase was observed. After being oxidized at 600 °C, the Al substrate near the interface was recrystallized thoroughly and the dislocation density of the oxidized sample was about an order of magnitude lower than that of the original sample.

Enhanced strength and fracture characteristics of the TiAl/Ti2AlNb laminated composite

In this study, TiAl/Ti2AlNb laminated composite has been prepared via vacuum hot-pressing sintering. The composite exhibits a good synergy between bending strength and ductility, with a significantly enhanced bending strength value of 910.25 MPa. The fracture characteristics in the TiAl alloy layer, Ti2AlNb alloy layer and interfacial α2-Ti3Al layer are separately elucidated. It is concluded that the slip bands, tunnel cracks (α2-Ti3Al layer), deflected microcracks (Ti2AlNb alloy layer), and microcracks (TiAl alloy layer) are involved in the fracture process. Moreover, the main deformation behaviors consist of dislocation glide and local microcracking. The formation of stack faults and twins is also observed in the TiAl alloy layer. Furthermore, we focus on revealing the relationship between the deformation behaviors and fracture process of the composite. In particular, the strain partitioning and delayed fracture, multistage synergetic deformation mechanisms, and specific microcrack initiation are discussed. These findings are important for investigating the fundamental mechanisms and serving as a guide for the design of high-performance laminated composites.

Construction of a High-Stability and Low-Nucleation-Barrier Cu3Sn Alloy Layer on Carbon Paper for Dendrite-Free Li Metal Deposition.

The construction of three-dimensional lithiophilic hosts is one of the most effective approaches for achieving the uniform nucleation and alleviating the volume changes of the Li metal. Unfortunately, some lithiophilic materials suffer from severe mechanical degradation resulting from the large volume expansion during lithiation, which causes a heterogeneous Li deposition. Herein, a low-nucleation-barrier Cu3Sn alloy layer on a carbon paper (Cu3Sn/CP) is constructed by a facile co-electrodeposition method for the Li anode framework. Density functional theory calculations show that the Cu3Sn alloy has a higher binding energy (-2.31 eV) than pure Sn (-1.97 eV) due to the electron-deficient state of Sn in the alloy phase, which enables the lithiophilic Sn to have increased affinity for Li. Additionally, the uniformly distributed Cu particles can evenly disperse the electric field on the surface of the carbon fiber and act as a "metal barrier" to inhibit the volume expansion of the Sn particles during lithiation, thereby enhancing the electrochemical stability of the alloy modification layer. As a result, the Cu3Sn/CP anode framework exhibits an exceptionally low nucleation overpotential (∼10 mV), a high and steady Coulombic efficiency (>98.5% for more than 200 cycles), and a long lifespan up to 1150 h. The full cells with LiFePO4 as a cathode show favorable cycling performance at 1 C with a capacity retention rate of 95.2%. The construction of the Cu3Sn alloy layer in this work sheds light on the design of a high-stability lithiophilic host for the dendrite-free Li metal anode.

Nano silica aerogel-induced formation of an organic/alloy biphasic interfacial layer enables construction of stable high-energy lithium metal batteries

Lithium metal batteries represent promising candidates for high-energy-density batteries, however, many challenges must still be overcome, e.g., interface instability and dendrite growth. In this work, nano silica aerogel was employed to generate a hybrid film with high lithium ion conductivity (0.6 mS cm−1 at room temperature) via an in situ crosslinking reaction. TOF-SIMS profile analysis has revealed conversion mechanism of hybrid film to Li–Si alloy/LiF biphasic interface layer, suggesting that the Li–Si alloy and LiF-rich interface layer promoted rapid Li+ transport and shielded the Li anodes from corrosive reactions with electrolyte-derived products. When coupled with nickel-cobalt-manganese-based cathodes, the batteries achieve outstanding capacity retention over 1000 cycles at 1 C. Additionally the developed film coated on Li enabled high coulombic efficiency (99.5%) after long-term cycling when coupled with S cathodes. Overall, the results presented herein confirm an effective strategy for the development of high-energy batteries.

Study on the Solidification Behavior of Inconel617 Electron Beam Cladding NiCoCrAlY: Numerical and Experimental Simulation

To better control the Inconel617 electron beam cladding solidification process, a three-dimensional temperature field model was built to simulate the temperature gradient, cooling rate, and solidification rate in the solidification process and take a deep dive into the solidification behavior, as well as the calculation of the solidification characteristic parameters at the edge of the molten pool and then predict the solidification tissue structure. The study shows that the largest temperature gradient occurred in the material thickness direction. The self-cooling effect of the material dominated the solidification of the alloy layer; the cooling rate depended on the high-temperature thermal conductivity of the material and the self-cooling effect of the matrix, and the maximum cooling rate in the bonding zone was 1380 °C/s. The steady-state solidification rate was equal to the moving speed of the heat source; the solidification characteristics of the solidification process at the edge of the molten pool increased with the distance from the surface: the cooling rate decreased from 1421.61 to 623 °C/s, the temperature gradient increased from 0.0723 × 106 to 0.417 × 106, and the solidification rate decreased from 0.01 to 0 m/s. The prediction was made that the small and thin equiaxed crystals are on the top, a thin and short dendritic transition structure in the middle, and relatively coarse dendrites at the bottom. Experiments confirmed that the solidification tissue structure is basically consistent with the simulation law.

Variation of spin-orbit torque and spin transport properties by V alloying in β-W-based magnetic heterostructures

Of transition metals, β-W exhibits the maximum charge-to-spin conversion efficiency. However, due to the lack of phase stability, the β-W-based alloy has rarely been investigated as a spin current generating layer. This study examines W–V alloy layers with various W100-xVx/CoFeB/MgO/Ta heterostructure compositions. X-ray diffraction confirms that the β-W matrix is conserved up to a V content of 20 at%. We attain a maximum damping-like torque efficiency of −0.45 ± 0.04 for the W80V20 alloy-based heterostructure through the harmonic response method. Furthermore, we determine the spin diffusion length of the W80V20 layer and specify the interfacial spin transparency of the W80V20/CoFeB structure by adopting the spin diffusion model. Consequently, we suggest an intrinsic spin-Hall angle of −0.86. In addition, we observe in-plane current-induced switching. Our results establish the potential of the β-phase W-V alloy layer as a spin current source layer in spintronic devices.

Refractory WMoNbVTa high-entropy alloy as a diffusion barrier between a molybdenum substrate and MoSi2 ceramic coating

Coating a MoSi2 ceramic layer on Mo substrates is an excellent strategy to enhance their oxidation resistance at elevated temperatures. Suppressing elemental interdiffusion across the Mo/MoSi2 interface is very important for extending the service life of Mo substrates. The present study attempted to develop a WMoNbVTa high-entropy alloy (HEA) layer as a diffusion barrier at the Mo/MoSi2 interface. A new double-layer WMoNbVTa/MoSi2 coating was fabricated on Mo substrates through a two-step spark plasma sintering (SPS) method. Then, the interdiffusion behaviors of Mo/WMoNbVTa/MoSi2 and Mo/MoSi2 systems at 1200–1500 °C were investigated comparatively. A WMoNbVTa HEA powder with a single body-centered cubic (BCC) structure was prepared through mechanical alloying and the intermediate WMoNbVTa HEA layer was successfully fabricated using the milled HEA powder. After long-term oxidation, two diffusion layers of Mo5Si3 and (WMoNbVTa)5Si3 appeared at the WMoNbVTa/MoSi2 interface, while no apparent diffusion zone was found at the Mo/WMoNbVTa interface. The growth rate of the thickness of the diffusion layer at the Mo/WMoNbVTa/MoSi2 interface was much lower than that at the Mo/MoSi2 interface. The WMoNbVTa HEA layer effectively suppressed the interdiffusion of alloying elements between the Mo substrate and MoSi2 ceramic coating. This is attributed to the sluggish diffusion effect of the WMoNbVTa HEA during high-temperature oxidation. The results suggest that WMoNbVTa HEA can be a suitable diffusion barrier between Mo substrates and MoSi2 ceramic coating.

BUILDING OF ALLOYED SURFACE LAYER DURING ELECTRIC SPARK TREATMENT OF STEEL 35 BY THE RHENIUM

He article presents the influence of the modes of electric spark placement of the alloyed layer on the surface of steel 35 during electric spark alloying using rhenium anode material. The use of this method allowed material scientists to develop a number of new technologies for creating protective alloyed layers of surfaces made of conductive materials with specified functional properties. (Research purpose) The research purpose is studying the effect of electric spark alloying modes during the layering of alloyed layers on steel 35 using rhenium anode material, to study the kinetics of the electro-mass transfer of the anode material to the surface depending on the energy in the pulse and its duration. (Materials and methods) Rhenium Re (99.99 percent) was used as the anode material, the cathode was steel 35. The next equipment was used: BIG-1, Elitron-22-AM with AG-2 unit, IMEIL installation; EVO-50 XVP S. ZEISS SEM, RigakuMiniFlex-II diffractometer (Japan), Cu-Ka radiation, ICDD database; scales VLO-200, VLR-220; micro hardness tester PMT-3M. The samples were cleaned in an ultrasonic bath. (Results and discussion) The data of the total change in the erosion of the anode, the gain of the cathode, the coefficient of electric mass transfer in various modes were obtained. The highest average mass transfer coefficient was observed with electric spark alloying with the highest energy values of 1.8 (62.2 percent) and 0.32 joules (37.4 percent) at the lowest frequencies of 20 and 80 hertz. The ratio of the values of energy and depth of the alloyed layer shows a tendency to decrease the depth with increasing energy and increase with increasing frequency. (Conclusions) The article describes the results of the study of the effect of the modes of electrospray alloying of 35 rhenium steel on the kinetics of mass transfer, elemental, phase composition.

Physical-mechanical properties of synthesized layers of Ti-Ni-Nb-based surface alloys, formed on the surface of TiNi alloy

The physical-mechanical properties (microhardness, Young's modulus, plasticity characteristic, shape recovery ratio) of the synthesized layers of Ti-Ni-Nb-based surface alloys of ~2 μm thickness, formed on the surface of TiNi alloy by the additive thin-film electron beam method were investigated by the instrumented indentation. It was found that the change in physical-mechanical properties in the synthesized surface alloys based on Ti-Ni-Nb is due to their layered structure. In particular, it is due to the thickness of the sublayers, their phase composition, and the structural states of the phases (nanocrystalline and amorphous). It was established that high strength and elastic-plastic parameters of the outer layer and a monotonic change in the physical-mechanical properties from the surface to TiNi substrate are provided in the surface Ti-Ni-Nb alloy with a lower volume fraction of the amorphous phase in the synthesized layers. It was found that the multilayer structure of the surface Ti-Ni-Nb alloy and the monotonically change in the physical-mechanical properties to the substrate ensure high mechanical compatibility of the synthesized layers of surface alloys with the TiNi substrate. Keywords: nickel titanium alloy, additive thin-film electron-beam synthesis, surface alloy, structure, physical-mechanical properties.

Effect of Scanning Speed on Properties of Laser Surface Remelting Layer of CuCr Alloy

Effect of Scanning Speed on Properties of Laser Surface Remelting Layer of CuCr Alloy

Адаптация структуры приповерхностных слоев антифрикционных медных сплавов при трении с различными смазочными материалами

Адаптация структуры приповерхностных слоев антифрикционных медных сплавов при трении с различными смазочными материалами

Composition of surface layers of titanium VT6 alloy after implantation of tantalum ions

The paper presents the results of the investigation of the surface layer composition of titanium alloy VT6 obtained after ion implantation with tantalum ions. It is shown that tantalum ion implantation can lead to a significant reduction in surface roughness, as well as a beneficial effect on the corrosion properties of the titanium alloy.