Alloy Layer Research Articles

Structure and properties of surface layer of TiNi alloy subjected to ion-plasma- and ultrasonic treatment

The paper presents the results of research on morphology, elemental composition, microhardness, corrosion properties of the surface layer of TiNi alloy subjected to ion-plasma (vacuum-arc method) deposition of TiN coating and ultrasonic treatment (UT) with different number of passes (n). The SEM method showed that ultrasonic treatment provides a significant reduction in the amount of the droplet phase on the TiN coating surface. The surface discontinuity of TiN coating at local points was observed with an increase in the number of passes during ultrasonic treatment. The effect of combined processing methods on the microhardness of TiNi sample was studied. It was shown that the synergistic effect can be observed for two hardening methods. The combined strengthening method increased the microhardness of TiNi alloy (1.6 GPa in the as-received state): due to the deposition of a TiN coating – up to 10.9 GPa, due to subsequently ultrasonic treatment – up to 14.5–18.4 GPa depending on the number of passes. For UT + TiN scheme, it was shown that the open circuit potential Ecorr was about –250 mV which is practically independent of the number of passes and determined by the potential value of TiN coating. For TiN + UT scheme, it was found that with an increase in the number of passes, the value of Ecorr shifts towards more negative values approaching the open circuit potential value of the TiNi sample in the as-received state (–350 mV). The analysis of Scanning Vibrating Electrode Technique (SVET) results showed high electrochemical compatibility of substrate (TiNi) and coating (TiN) materials in a chloride environment with minimal current density fluctuations for the samples subjected to UT + TiN and TiN + UT (n = 1). The proposed method for TiNi alloy treatment according to TiN + UT scheme (n = 1) promotes an improvement of surface morphology and corrosion resistance.

Oxidation behavior of Ti55 alloy and TiBw/Ti55 composites and antioxidation mechanism of TiBw in composites at 960–1000 °C

The oxidation behavior of Ti55 alloy and TiBw/Ti55 composites at temperatures ranging from 960 to 1000 °C was investigated by characterizing the surface and cross-section microstructure of specimens. Results showed that TiBw reinforcement accelerated the occurrence of Ti6O/Ti3O by dissolving oxygen in titanium in the starting oxidation stage, and the Ti6O/Ti3O transformed into TiO2 with the progression of oxidation. Meanwhile, TiBw reinforcement promoted the formation of (101) crystal planes to be beneficial to the growth of TiO2 twins. The cross-sectional characterization showed that the oxide layer of Ti55 alloy and TiBw/Ti55 composites from outside to inside was TiO2+Al2O3, TiO2, Ti-Sn compounds, Ti6O/Ti3O in sequence, which was confirmed by calculating the standard Gibbs free energy of the oxide nucleation. The TiBw reinforcement accelerated the occurrence of suboxides Ti6O/Ti3O by dissolving oxygen in titanium, and promoted the formation of (101) crystal planes which were beneficial to the growth of TiO2 twins. The optimal addition of TiBw induced the TiO2 twins, promoted the random orientation of oxides and refined the oxide size of the TiBw/Ti55 composites with 3.5 % volume fractions of TiBw, resulting in the best resistance against oxidation.

Fatigue life of S960 high strength steel with laser cladded functional surface layers

This study evaluates the fatigue life of S960 high-strength steel with laser-cladded layers of aluminium bronze, hard chrome, cobalt alloy, and stainless steel, using three-point bending tests. Our results demonstrate that while these cladded layers offer potential for enhanced surface properties, they generally reduce the material’s fatigue life due to alterations in the heat-affected zone and the introduction of microstructural defects at layer interfaces. The extent of fatigue life reduction varies with the type of cladded layer, highlighting the importance of optimizing laser cladding parameters to minimize detrimental effects and improve component longevity.

Identification of temperature and diffusion effects during helium swelling of the surface layer of a TiTaNbV alloy

The article presents the comprehensive analysis results of the connection between structural changes caused by the effects of deformation swelling and softening effects during high-dose irradiation with He2+ ions, alongside determines the kinetics of changes in structural and strength parameters contingent upon irradiation conditions (in the case of irradiation temperature variations). The interest in such studies is due to the need to study the influence of temperature factors on the diffusion mechanisms of implanted He2+ into the damaged layer of a high-entropy TiTaNbV alloy in the case of high-dose irradiation. At the same time, the study of such mechanisms makes it possible to determine not only the radiation resistance of TiTaNbV alloys, but also to expand the general understanding of the influence of the structural features of high-entropy alloys associated with deformation distortion of the crystal structure, which prevents diffusion and migration mechanisms of defect propagation in the damaged layer. During determination of changes in strength properties depending on irradiation conditions, it was found that irradiation temperature growth leads to both a rise in the degree of softening under high-dose irradiation and an increase in the thickness of the softened layer under high-dose irradiation. These changes indicate that at high temperatures, the diffusion of implanted ions is not restrained by structural distortions, which results in their migration to a greater depth exceeding the ion travel depth, which should be considered when designing the use of these alloys in the case of their operation in extreme conditions.

Enhancing wear resistance, anti-corrosion property and surface bioactivity of a beta-titanium alloy by adopting surface mechanical attrition treatment followed by phosphorus ion implantation

A two-step method of surface mechanical attrition treatment (SMAT) followed by phosphorous (P) ion-implantation was adopted to treat Ti-25Nb-3Mo-2Sn-3Zr (named as TLM) alloy. The initial SMAT process refined the grains from micrometer-scale to about 10–30 nm, and begot the TLM surface much rougher with apparently improved hydrophilicity. The subsequent P ion-implantation led to the formation of a hybrid structure of the TiP, β-Ti nanograins and P-interstitial amorphous in the surface layer of the TLM alloy, and resulted in a slight decrease of the surface roughness and wettability of the SMAT-processed alloy. The indentation, tribology and potentiodynamic polarization tests indicated that the SMAT procedure concurrently enhanced the microhardness, wear-resisting property and corrosion resistance of the TLM alloy, and the followed P-ion implantation could further improve these tested properties. Moreover, the P-ion implanted TLM alloy was verified to exhibit much better surface bioactivity (including biomineralization in the simulated body fluid (SBF) and in-vitro cell adhesion) as compared to the original TLM alloy. With the remarkable improvements of the wear resistance and anti-corrosion property as well as the surface bioactivity of the P ion-implanted TLM alloy, our study provides an alternative avenue to fabricating new-type Ti-based orthopedic implants with superior comprehensive performance.

Mechanism of Formation of Surface Protective Layer in Heat-Resistant HP40NbTu Alloys during High-Temperature Oxidation

Mechanism of Formation of Surface Protective Layer in Heat-Resistant HP40NbTu Alloys during High-Temperature Oxidation

The refined microstructure and enhanced properties of the Al-Mo laser-alloyed layer after high-current pulsed electron beam irradiation

The aim of this study is to investigate the microstructure and properties of the AlMo laser-alloyed layer induced by high-current pulsed electron beam (HCPEB) irradiation. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were utilized to investigate the microstructures of the modified layer. The microhardness and friction properties were also measured. The microstructural observation shows that HCPEB irradiation led to the formation of a modified layer approximately a dozen microns thick, which was the absence of the pores. It was found that the flower- and strip-like AlMo particles were dissolved to form nano-size particles consisting of Al5Mo (h2), Al12Mo, and Al17Mo4 phase after HCPEB irradiation. Additionally, the slip bands and high-density dislocations were formed in the modified layer. The refined microstructure significantly enhanced the microhardness of the laser-alloyed layer. A quantitative evaluation was conducted to investigate the individual contributions of four strengthening mechanisms to the strength of the modified layer, which indicated that dislocation and grain boundary strengthening were dominant. The results of sliding wear tests show that the modified layer exhibited superior properties compared to the laser alloying layer, which was attributed to the formation of crystal defects, solid solutions, and nanoparticles.

Micrometer-sized 3D porous structure decorated with uniform InSb alloy layer towards dendrite-free Li metal electrode

Li metal electrode is expected to be one promising anode to construct high energy density batteries because of its high theoretical specific capacity and the lowest electrode potential. However, uncontrollable dendrite growth and large volume changes cause batteries failure and safety risks. Here, an InSb alloy modified three-dimensional porous Cu (3D Cu@InSb) is constructed by electroless plating coupled with electroplating to stabilize the Li metal electrode. The suitable 3D porous structure with pore size of several micrometers can provide uniform current distribution, rapid ionic transferring channels, and effectively accommodate volumetric changes and release stress as well, avoiding the limited modifying effect using too large pores and poor ionic transport kinetics using too small pores. Moreover, the InSb alloy modified layer with high binding energy to Li+ reduces the nucleation overpotential and enhances the Li plating/stripping reversibility. Under the synergistic effects of InSb alloy modified layer and suitable 3D porous structure, Li metal is uniformly plated/stripped in pores with almost thorough flat surface even under a high area capacity of 4 mAh cm−2. The full battery assembled using LiFePO4 (LFP) cathode demonstrates a long life of 600 cycles at 2 C with a capacity retention of 86 %.

Tailoring nanoscale primary silicon in laser powder bed fusion for high-performance lithium-ion battery anodes

Silicon-based anodes, utilizing nanosized silicon materials, hold great promise for the next-generation of lithium-ion batteries due to their high capacity and stable expansion. This study aims to address challenges in traditional slurry-coated anodes, such as agglomeration and low adhesive strength, through the application of laser powder bed fusion (LPBF). The process involves fabricating an Al-Si-Cu alloy layer on a Cu foil current collector, followed by dealloying to create a porous Si-Cu anode. Simulated and experimental results demonstrate successful alloy layer formation through optimized laser spot (55 μm) and powder sizes (1–5 μm). Controlled cooling produces primary Si particles ranging from 150 nm to 1 μm. The resulting microstructure enhances electrochemical performance, particularly by tailoring the size of primary Si. The resultant porous Si-Cu anode, featuring uniformly distributed primary Si (200 nm) metallurgically bonded with Cu networks, exhibits an initial coulombic efficiency of 83% and a remarkable capacity retention of 80% after 300 cycles at 2 C. In-situ and ex-situ observations confirm the crucial role of anode architecture in performance enhancement. This study elucidates the influence of the LPBF microstructure on anode performance and broadens the potential application of laser powder bed fusion in battery manufacturing.

Effect of synergistic action of anodising and graphene on the mechanical properties of fibre-reinforced metal laminates

Fibre reinforced metal laminates (FMLs) are widely used in various fields due to their excellent properties. However, the weak interlayer properties of FMLs limit their applications. In this paper, the interlayer properties of FMLs are enhanced by anodising the 2024-T3 aluminium alloy layer in FMLs or by epoxy matrix modification of graphene nanoplatelets (GNPs). The effect of both synergistic impacts on the interlayer properties of most FMLs is investigated. The FMLs were manufactured using the wet lay-up technique using 2024-T3 aluminium alloy, E51 epoxy and EW100 glass fibre. The results showed that the type I fracture toughness, tensile strength, flexural strength, interlayer shear strength and single layer shear strength of FMLs after anodic oxidation treatment were increased by 406.4%, 10.3%, 18.3%, 42.6% and 28.3%, respectively, compared with those of pure FMLs. The type I fracture toughness, tensile strength, flexural strength, interlayer shear strength and single layer shear strength of the GNPs-modified FMLs matrix were increased by 280.4%, 3.7%, 6.8%, 34.5% and 19.1%, respectively, compared with those of pure FMLs. Moreover, the synergistic effect of FMLs indicates that the simultaneous anodic oxidation and GNPs modification of FMLs can lead to the best mechanical properties of FMLs. Microscopic images and schematics illustrate the toughening mechanism of anodising and GNPs, including the enhancement of aluminium/resin interface and fibre/resin interface and the enhancement of resin matrix properties.

Revisiting porous foam Cu host based Li metal anode: The roles of lithiophilicity and hierarchical structure of three-dimensional framework

Lithium (Li) metal anode (LMA) is one of the most promising anodes for high energy density batteries. However, its practical application is impeded by notorious dendrite growth and huge volume expansion. Although the three-dimensional (3D) host can enhance the cycling stability of LMA, further improvements are still necessary to address the key factors limiting Li plating/stripping behavior. Herein, porous copper (Cu) foam (CF) is thermally infiltrated with molten Li-rich Li-zinc (Li-Zn) binary alloy (CFLZ) with variable Li/Zn atomic ratio. In this process, the LiZn intermetallic compound phase self-assembles into a network of mixed electron/ion conductors that are distributed within the metallic Li phase matrix and this network acts as a sublevel skeleton architecture in the pores of CF, providing a more efficient and structured framework for the material. The as-prepared CFLZ composite anodes are systematically investigated to emphasize the roles of the tunable lithiophilicity and hierarchical structure of the frameworks. Meanwhile, a thin layer of Cu-Zn alloy with strong lithiophilicity covers the CF scaffold itself. The CFLZ with high Zn content facilitates uniform Li nucleation and deposition, thereby effectively suppressing Li dendrite growth and volume fluctuation. Consequently, the hierarchical and lithiophilic framework shows low Li nucleation overpotential and highly stable Coulombic efficiency (CE) for 200 cycles in conventional carbonate based electrolyte. The full cell coupled with LiFePO4 (LFP) cathode demonstrates high cycle stability and rate performance. This work provides valuable insights into the design of advanced dendrite-free 3D LMA toward practical application.

Corrosion Behavior of CMT Cladding Layer of AZ91 Magnesium Alloy Subjected to Friction Stir Processing.

Friction stir processing (FSP) was performed on an AZ91 magnesium alloy cladding layer fabricated by a cold metal transfer (CMT) technique. Electrochemical properties and immersion corrosion behavior of the cladding layer before and after FSP in 3.5 wt.% NaCl solution were investigated. After applying the FSP, the corrosion potential and corrosion current density of the cladding layer increased from -1.455 V to -1.397 V and decreased from 4.135 μA/cm2 to 1.275 μA/cm2, respectively. The results of OM and SEM displayed the refinement of grains and the dispersion of β-Mg17Al12 second phase in the friction stir processed (FSPed) cladding layer and more severe corrosion of the unprocessed sample. The corrosion rate of the FSPed cladding layer was lower, and a more compact corrosion product film was formed on the surface of the FSPed cladding layer. EDS results and XRD patterns showed that the corrosion products was mainly composed of Mg(OH)2. The increase in Al content in the α-Mg matrix, grain refinement, and fragmentation and dispersion of the β-Mg17Al12 second phase induced by FSP were the main factors that led to the improvement in corrosion resistance of the cladding layer of the AZ91 magnesium alloy fabricated by CMT.

Constructing heterogeneous micro/nano multilayer structure in Al alloys via solute grain boundary segregation for superior strength-ductility synergy

A heterogeneous micro/nano multilayered (HM/NMed) Al/Al-0.5 wt%Cu composite, composed of alternating coarse-grained pure Al layers and nanostructured Al-0.5 wt%Cu alloy layers containing a nanolamellar structure (NLS) with lamellar thickness as small as ∼60 nm, was developed by accumulative roll bonding (ARB) followed by low temperature annealing. Deformation induced Cu atoms grain boundary (GB) segregation was observed in Al-0.5 wt%Cu layer, which is responsible for the formation and stabilization of the NLS in the Al-0.5 wt%Cu alloy layers. This resultant HM/NMed Al/Al-0.5 wt%Cu composite with dramatic difference in microstructure and strength/hardness between neighboring pure Al and Al-0.5 wt%Cu alloy layers can achieve an exceptional strength-ductility combination: a yield strength close to the NLSed Al-0.5 wt%Cu alloy, and a tensile ductility comparable to coarse-grained pure Al. Strong hetero-deformation-induced (HDI) strengthening associated with the activation of stacking faults, are responsible for this exceptional strength-ductility synergy. The results presented here demonstrate a general design strategy based on solute GB segregation that enables the fabrication of HM/NMed Al-based materials with multi-scale hierarchical microstructures and improved mechanical properties.

The inhibition of the interaction between CVD SiC and GH3535 alloy in molten LiF-NaF-KF salt by the Li metal

The effect of Li metal on the interaction mechanism between CVD SiC and GH3535 alloy in molten LiF-NaF-KF salt at 700 °C was investigated. SiC and alloy interacted with each other in salt to result in the corrosion of GH3535 alloy (∼200 μm for 1000 h). The reactions among impurities, corrosion products, GH3535 alloy, and SiC in salt formed Cr3C2 and Ni2Si. The Li metal reacted with the impurities and the corrosion products to inhibit the formation of Cr3C2 and decrease the total depth of corrosion layer and deposition layer of alloy to ∼30 μm for 1000 h.

Design and theoretical analysis of SPR biosensors based on gold-silver alloy and protective top layer for enhanced biosensing applications

In this paper, we present a theoretical study to enhance the performance of SPR biosensor structures based on the Kretschmann configuration. We use a low refractive index CaF2 prism, a gold-silver alloy (Au10Ag90), different protective top layers, and water as a sensing medium (SM). Our results show that a structure with CaF2 prism, Au10Ag90, and SM achieves a sensitivity of 280⁰/RIU. The addition of different cover layers to this structure such as graphene, SiO2, BaTiO3, Fe2O3, and Al2O3 improves the sensitivity to 300⁰/RIU, 340⁰/RIU, 340⁰/RIU, 360⁰/RIU, and 420⁰/RIU, respectively. Finally, we conclude that the structure with Al2O3 has the best simulation results in terms of sensitivity of 420⁰/RIU, then Figure of Merit (FoM) of 83.83/RIU, and Quality Factor (QF) of 176.05/RIU. We also discuss the experimental feasibility of this work. The proposed biosensors can be used in different biological sensing applications and specifically, in the detection of cancer bio-markers in body fluids.

Biocompatibility and Antibacterial Properties of NiTiAg Porous Alloys for Bone Implants.

In order to reduce infections, porous NiTi alloys with 62% porosity were obtained by self-propagating high-temperature synthesis with the addition of 0.2 and 0.5 at. % silver nanoparticles. Silver significantly improved the alloys' antibacterial activity without compromising cytocompatibility. An alloy with 0.5 at. % Ag showed the best antibacterial ability against Staphylococcus epidermidis. All alloys exhibited good biocompatibility with no cellular toxicity against embryonic fibroblast 3T3 cells. Clinical evaluation of the results after implantation showed a complete absence of purulent-inflammatory complications in all animals. Even distribution of silver nanoparticles in the surface layer of the porous NiTi alloy provides a uniform antibacterial effect.

Electrochemical behavior and separation of ytterbium from NaCl-CaCl2 molten salt by reactive electrodes

To electro-extract Yb from NaCl–CaCl2 molten salt, the electrochemical behavior of Yb(III) was studied by cyclic voltammetry (CV), square wave voltammetry (SWV), chronopotentiometry (CP) and open circuit chronopotentiometry (OCP) on inert Mo and reactive Ni and Cu electrodes in NaCl–CaCl2 molten salt at 923 K. It was found that Yb(III) was reduced to Yb(II) on the Mo electrode and no Yb metal was formed prior to the reduction of Na+/Ca2+ ions, suggesting that the electroreduction of Yb(II) to Yb on inert Mo electrode is impossible. The diffusion coefficient of Yb(III) was determined by CV and CP and the results by the two methods showed good consistency. However, the reduction peaks of four Ni-Yb and five Cu-Yb intermetallic compounds were formed on reactive electrodes Ni and Cu, respectively. Thus, the reduction of Yb(II)/Yb became possible by this cathodic alloying method. To investigate the feasibility of the separation of ytterbium from this molten salt, potentiostatic electrolysis were carried out at −1.83 V, −2.0 V, −2.2 V, and −2.4 V (vs. Ag/AgCl) respectively on the Ni electrode and at −2.1 V (vs. Ag/AgCl) on the Cu electrode. The results showed that the yield of Yb atoms in the electrolytic alloy layer becomes higher when the applied potential shifts negatively, and Ni electrode is confirmed more suitable than Cu material for Yb separation in NaCl–CaCl2 molten salt.

Formation of Surface Deformed Layer of AZ31 Magnesium Alloy Subjected to Conventional Mechanical Grinding

Formation of Surface Deformed Layer of AZ31 Magnesium Alloy Subjected to Conventional Mechanical Grinding

Solid-phase transient soldering method based on Au/Ni–W multilayer thin-film-modified copper-based structures

The copper crystal cone-shaped micro-nanostructure is used as the substrate, and the Ni–W alloy layer and Au nanolayer are plated sequentially. Instantaneous soldering with lead-free solder is realized under ultrasonic assistance at room temperature. This solves the residual stress and thermal damage caused by high melting point lead-free solder on thin chips and thermal components, and ensures the safety and reliability of electronic components. Copper-based microstructures are deposited by electrochemical methods. An amorphous Ni–W alloy layer with a thickness of 180 nm is deposited on the Cu-based microstructures by adjusting the atomic ratio of the plating solution. The Ni–W layer is further coated with a 50 nm Au layer to prevent oxidation. Solid-phase transient soldering is realized by combining the Au/Ni–W multilayer thin-film-modified Cu substructures with commercial solder (SAC305) for a holding time of 3 s at a soldering pressure of 10,000 gf (20 MPa) while ultrasonically assisted. The soldered samples are aged at 180 °C for 10 min, 30 min, and 60 min, respectively. Copper substructures with different surface modifications are subjected to destructive shear experiments with solder balls. Scanning electron microscope and X-ray fluorescence thickness gauge are used to study the microstructure, intermetallic compound (IMC) composition thickness and properties of the soldered interface and section. The cone height of the Cu-based structure is 2–4 μm, and the diameter of the bottom is 800 nm–1200 nm, which has a sharp tip and an excellent L/D ratio. The interface between the Au/Ni–W modified Cu substructure and the solder ball is almost free of holes. The average shear strength at the soldering interface is about 43.06 MPa. The fracture surface after the shear experiment basically occurs inside the solder ball matrix, which belongs to the pure toughness fracture. The interface between the Au/Ni–W-modified Cu-based structure and the solder ball is subjected to long aging treatment at 180 °C. The soldering interface showed a “bright layer”. New phases are generated on the solder side above the “bright layer”, while no new phases appear on the Cu substructure side below the “bright layer”. The copper-based microstructure is inserted into the inside of the solder ball to form an inlay and produce mechanical interlocking. Au/Ni–W alloy modification layer can effectively improve the surface hardness of copper-based structures. This creates a large hardness difference with soft solder and enables the formation of fewer holes in the insertion solder. Amorphous Ni–W alloys are prone to form dense oxide films during ultrasonication. The Au film modification prevents oxide generation and increases the average shear strength of the soldering interface. The Ni–W alloy layer retards the interdiffusion between Cu–Sn, blocks the excessive growth of Cu–Sn IMCs, and reduces the reliability problems caused by interface failure.

Protective layers of zirconium alloys used for claddings to improve the corrosion resistance

Abstract Zirconium alloys are used as a cladding material for fuel elements in nuclear reactors. In the case of severe accident conditions, the possible rapid oxidation of zirconium in steam or/and air may result in intense hydrogen generation and hydrogen–oxide mixture explosion. Advanced technologies for increasing the corrosion resistance of claddings are being investigated in two directions: (a) protective coatings on Zr alloys and (b) the use of new materials for claddings. Coatings with silicon may provide a more protective barrier than the ZrO2 films formed on an alloy cladding during nuclear plant operations. These coatings may also serve as a protective barrier during high-temperature accidents. The current work aimed at developing protective coatings with silicon on zirconium alloys. Multielemental Zr–Si–Cr coatings were formed on Zry-2 alloy using the physical vapor deposition (PVD) method. Long-term oxidation tests were carried out under the following conditions: 360°C/195 bar/63 days/water-simulating PWR water. Obtained results show the protective character of formed layers. The material in the form of silicon carbide grains covered with yttrium–aluminum garnet (SiC + YAG) was prepared using the sol–gel method. The formed powder is the main component for coating formation on Zr–1Nb alloy using the method of suspension plasma spraying (SPS).