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Nickel coatings are electrodeposited onto Al0.95Mg0.05 substrates and heat treated to improve the mechanical properties of aluminum alloys. Al0.95Mg0.05 samples were electroplated for varying durations in a stirred nickel-plating Watts bath. The coating adhesion and surface mechanical properties were then improved by heat treatment at 450, 500, and 550 °C with annealing times ranging from 1 to 40 h depending on the diffusion temperature. Microstructural studies using optical microscopy, scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy, and x-ray diffraction reveal that heat treatment results in varying amounts of Al3Ni2 and Al3Ni intermetallic phases. Berkovich microindentation was used to determine sample hardness, and wear tests were performed with a ball-plane tribometer with alternating translation motion. The results show that as-treated substrates have a higher hardness than the original Al0.95Mg0.05 substrates due to the various (Al, Ni) intermetallic growths. The time of Ni deposition in the bath and the temperature/time of annealing influence the intermetallic type, thickness, and crystallinity. In addition, wear behavior demonstrates that unreacted Ni on the top surface is harmful and causes the running-in stage and that after several runs, the coefficient of friction of the as-prepared samples stabilizes between 0.3 and 0.36. [ABSTRACT FROM AUTHOR]

A novel quaternary medium-entropy rock-salt oxide (Mg 0.25 Co 0.25 Ni 0.25 Zn 0.25)O (MERO) was predicted using first-principles calculation and prepared through solid-state reaction. The first-principles study demonstrated that the mixing enthalpy and entropy values of the MERO are 2.377 kJ/mol and 0.693–1.040 R, respectively. The single-phase MERO can be obtained from 1000 °C to 1200 °C, demonstrating good thermal stability, whereas a completely disordered occupancy of different metal cations can be confirmed by Raman spectroscopy. The Transition Electron Microscope (TEM) analysis reveals that the MERO exhibits an FCC structure with a lattice parameter of 4.384 Å. The dielectric permittivity ε r of MERO prepared at 1200 °C shows relatively high values of 6.4 × 103 and 18.40 corresponding to frequencies of 100 Hz and 1 MHz at room temperature, exhibiting a potential for application in electrode materials and capacitors. [ABSTRACT FROM AUTHOR]

Due to its great efficiency, the electrocatalytic nitrogen reduction reaction (NRR) presents itself as a viable and eco-friendly substitute for the traditional Haber-Bosch ammonia production process. However, it is still a formidable task to find electrocatalysts with high activity and selectivity. In this study, a series of transition metals (TM = Ti–Ni, Zr–Mo, Ru–Pd, and Hf–Pt) anchored on 1T′-dual-transition-metal dichalcogenides (1T′-d-TMDs) monolayers (TM 2 @1T′-CrCoS 4) were systematically investigated as electrocatalysts for NRR using first-principles calculations based on density functional theory. Based on a thorough examination of selectivity, high activity, and stability, Mn 2 @1T′-CrCoS 4 and Co 2 @1T′-CrCoS 4 demonstrate exceptional NRR performance. With a limiting potential of −0.11 V, Mn 2 @1T′-CrCoS 4 stood out among them in terms of catalytic activity, favoring the enzymatic pathway. Furthermore, ab initio molecular dynamics (AIMD) simulations were used to assess the dynamic stability of Mn 2 @1T′-CrCoS 4 and Co 2 @1T′-CrCoS 4. To determine the source of increased activities, the density of states (DOS), charge density difference, and crystal orbital Hamilton population analysis were used. According to our research, the 1T′-d-TMD S is a viable substrate for the development of effective NRR catalysts and offers a platform for electrocatalyst experimentation. [Display omitted] • 1T′-d-TMDs monolayers have been investigated as a new efficient electrocatalyst substitute in the electrocatalysis field. • The 1T′-CrCoS 4 with unique characteristics is potential electrocatalysis as the candidate material for NRR. • The NRR catalytic performance of TM dimer anchored on 1T′-CrCoS 4 is investigated. • The Mn 2 @1T′-CrCoS 4 exhibits excellent catalytic activity with a low limiting potential of −0.11 V. [ABSTRACT FROM AUTHOR]

The special wettability of superhydrophobic aluminum alloys has a broad applied foreground in important industrial fields, such as aviation, automobiles, and ships. However, the microstructures of superhydrophobic surfaces are easily destroyed, causing them to lose superhydrophobicity, which seriously restricts the application of superhydrophobic surfaces. To solve this problem, we developed a simple and low-cost fabrication method by the blasting and chemical deposition of Ni and P to process robust micro/nano-composite structures on an aluminum alloy material and then obtained a superhydrophobic nickel–phosphorus–aluminum surface (SHP-NiP-Al) with a water contact angle of 163° and a water rolling angle of 3° through low surface energy modification. The prepared SHP-NiP-Al had an excellent self-cleaning performance and antifouling property. In addition, it showed great mechanical robustness and chemical stability performance in the sand impact, blade scratch, and acid/base solution tests. It also demonstrated good corrosion resistance performance. Electrochemical corrosion tests indicated that the corrosion resistance of SHP-NiP-Al was better than that of the original aluminum. Moreover, SHP-NiP-Al could collect the water from the fog environment. This method is helpful for the practical use of superhydrophobic aluminum alloy surfaces. [ABSTRACT FROM AUTHOR]

Segregation of interface elements is the main factor affecting the corrosion activity of microareas around Al2O3 inclusions rather than galvanic corrosion. In this work, the effects of segregation of Cu, V, Ni, Mo, B, and P elements on the interfacial bonding strength and microareas corrosion activity around Al2O3 inclusions are analyzed in detail using 3D atomic probe and first‐principles calculations. In the results, it is shown that Cu, V, Mo, B, and P elements reduce the stability of the α‐Fe/Al2O3 interface. In addition, the segregation of Cu, V, Mo, B, and P elements at the interface also enhances the adsorption capacity of Cl and ultimately improves the microarea corrosion activity around Al2O3 inclusions. Ni element can enhance the stability of α‐Fe/Al2O3 interface, and the segregation of Ni element at the interface weakens the adsorption capacity of Cl and ultimately reduces the microarea corrosion activity around Al2O3 inclusions. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, the mechanical properties of orthorhombic phase Al1-xTMxP (x = 0.0625, 0.125, 0.25; TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) crystals were studied. By analyzing the mechanical stability, it was found that Al0.75Zn0.25P is mechanical unstable, and the rest all mechanical stable. The mechanical properties of Al1-xTMxP were studied, including Bulk modulus, shear modulus, Young's modulus, Poisson's ration, ductility, Vickers hardness, and elastic anisotropy. It was found that Al0.75Ni0.25P has the largest Bulk modulus, the largest Poisson's ratio. Al0.75Ni0.25P has the smallest shear modulus, the smallest Young's modulus and the smallest Vickers hardness. The Al0.75Ni0.25P has the best ductility. Al0.75Ni0.25P and Al0.75Cu0.25P show strong elastic anisotropy, and the Al0.75Cu0.25P has the largest elastic anisotropy. Through the study of the mechanical properties of Al1-xTMxP, it was found that doping Ni into AlP is an effective means to tune its mechanical properties. [ABSTRACT FROM AUTHOR]

Effective hydrogen storage is a crucial requirement for harnessing hydrogen as an energy source. Among various storage methods, solid-state hydrogen storage holds promise but necessitates extensive investigation. This study employs density functional theory within the WIEN2k code to improve the desorption temperature and kinetic properties of MgH 2 by introducing Be in combination with transition elements (Ni, Cu, and Zn). The gravimetric hydrogen storage capacity for all studied compounds exceeds 6%. Introduction of different transition elements with Be leads to improvements in formation and cohesive energies, as well as in desorption temperature. Mechanical stability, determined through elastic constants, is confirmed for all hydrides meeting the Born stability criteria. Detailed analyses encompass bonding characteristics, shear modulus, bulk modulus, Cauchy pressures, elastic anisotropy, and Vickers Hardness tests. Electronic properties reveal that Mg 2 BeZnH 8 exhibits the semiconductor nature, and properties are further improved by using TB-mBJ approach. Electronic charge density calculations unveil interatomic bonding nature. Numerous previously unexplored thermodynamic aspects of these hydrides have been investigated and are now presented. • Orthorhombic Mg 2 BeTMH 8 (TM = Ni, Cu and Zn) have been investigated by using density functional theory. • The gravimetric hydrogen storage capacity for all compounds studied exceeds 6%. • Mg 2 BeZnH 8 has low desorption temperature than other two studied hydrides. • All the studied materials are mechanically stable and hard. • Electronic properties reveal that these hydrides exhibit semiconductor nature, except Mg 2 BeNiH 8. [ABSTRACT FROM AUTHOR]

In the process of directed energy deposition-arc (DED-arc), the geometrical shape of weld bead in arc-striking (AS) and arc-extinguishing (AE) areas are usually inconsistent with that in the middle section, which directly affects the forming accuracy of component thus needs to be optimized. In this paper, high-speed photography is used to observe the molten pool behavior of nickel aluminum bronze (NAB) bead deposition, and the causes of abnormal bead shape in the AS and AE areas are analyzed. On that basis, an optimization method for AS and AE is put forward. In the AS area, the welding current and travel speed are increased. And after the arc strikes, a hovering time is used during which the torch hovers at the AS point. In the AE area, the welding current is gradually reduced while the torch keeps hovering at the AE point. Then, the optimization effect of AS parameters on the bead shape are explained through factorial experiments, and the optimization effects of AE parameters are explained through orthogonal experiments. At the same time, the optimal parameter combination of AS and AE is obtained. With the proposed method and the optimal parameters, the height and width deviation of the deposited single bead are controlled within 5%. After adopting the optimization method, the effective height ratio of the DED-arc–manufactured NAB thin wall is increased from 67.5% to 91.5% under the unidirectional deposition path, which is also increased from 88.9% to 98.3% under the bidirectional deposition path. [ABSTRACT FROM AUTHOR]

To study the effect of aluminum and nickel elements on the microstructures and properties of the nickel–aluminum bronze (NAB) alloy, four kinds of alloys with different compositions, ZCuAl7–7–4–2, ZCuAl8-6-4-2, ZCuAl9-5-4-2, and ZCuAl10-4-4-2, are prepared by vacuum-melting technology. The effects of different Al/Ni ratios on the microstructures of NAB are investigated using a metalloscope, scanning electron microscopy, transmission electron microscopy, and XPS analysis. The mechanical property is evaluated with microhardness testing and tensile mechanical testing. The corrosion resistance is evaluated using mass-loss testing, electrochemical testing, and corrosion-product characterization. The results show that with the increase of the Al/Ni ratio, the content of precipitated phases increases, while β′ and hard κ, which have a different morphology, appear. As the Al/Ni ratio rises from 1 to 2.5, the hardness increases from 104 HV to 202 HV, and the tensile strength increases by 394 MPa from 356 MPa to 751 MPa, but the elongation decreases substantially from 50.50% to 11.00%. The best corrosion resistance is shown on ZCuAl7-7-4-2, with a corrosion rate of 0.00267 mm/a after 30 d of static immersion corrosion in 3.5 wt.% NaCl solution. Through electrochemical testing and corrosion-product characterization, it is found that ZCuAl7-7-4-2 has the largest polarization resistance Rp, and the selective corrosion of the surface is mild. [ABSTRACT FROM AUTHOR]

The directed energy deposition-arc (DED-arc) process is gaining popularity for cost-effective production of large parts, especially in the marine industry. However, precise shaping control, especially for parts with sharp corners, has been challenging. Nickel aluminum bronze (NAB) alloy, widely used in the marine field, is an expensive material, making it crucial to improve its forming accuracy. To tackle this challenge, the Angle-Driven Parameter Control Model (APCM) has been introduced. This model is designed to enhance corner paths in the DED-arc process for NAB alloy. By adjusting the travel speed, the APCM aims to reduce height errors at corners. To validate the effectiveness of the APCM, single bead depositions and a multi-layer thin-wall component with seven different angles (10°, 20°, 30°, 45°, 60°, 75°, and 90°) were tested. Results indicate that the APCM has a more significant optimization effect at smaller angles. For angles above 60°, relatively small height deviations can be achieved without parameter control. For the 15-layer thin-wall component, the APCM control reduced the height deviation at the 10° angle from 7.72 to 2.09 mm. Therefore, the proposed APCM is ideal for corner paths in the DED-arc process of NAB alloy. [ABSTRACT FROM AUTHOR]

This study employs first‐principles calculations to investigate the structural stability, electronic properties, and elastic properties of Co‐, Ni‐, Cu‐, and Mo‐doped β‐Si3N4. After optimizing the structure of each doped system, it can be determined that all systems are stable structures, as evidenced by the binding energy and forming energy. Then, the electronic properties of the doped systems are analyzed using the energy band and density of states. The findings reveal that the introduction of Co, Ni, and, Cu, reduces the energy bandgap compared to pure Si3N4. More notably, the doping of Mo eliminates the bandgap and results in strong metallicity in the doped systems. Moreover, all doped systems display magnetic moments. Finally, the investigation of elastic properties shows that all doped structures are ductile. The doping of Co, Ni, Cu, and Mo metals improves the toughness of Si3N4. In addition, the doping change of Co is the most obvious. These findings provide a theoretical foundation for future research on the preparation of ductile Si3N4 ceramics. [ABSTRACT FROM AUTHOR]

This study employs first‐principles calculations to investigate the structural stability, electronic properties, and elastic properties of Co‐, Ni‐, Cu‐, and Mo‐doped β‐Si3N4. After optimizing the structure of each doped system, it can be determined that all systems are stable structures, as evidenced by the binding energy and forming energy. Then, the electronic properties of the doped systems are analyzed using the energy band and density of states. The findings reveal that the introduction of Co, Ni, and, Cu, reduces the energy bandgap compared to pure Si3N4. More notably, the doping of Mo eliminates the bandgap and results in strong metallicity in the doped systems. Moreover, all doped systems display magnetic moments. Finally, the investigation of elastic properties shows that all doped structures are ductile. The doping of Co, Ni, Cu, and Mo metals improves the toughness of Si3N4. In addition, the doping change of Co is the most obvious. These findings provide a theoretical foundation for future research on the preparation of ductile Si3N4 ceramics. [ABSTRACT FROM AUTHOR]

The impact of a dopant (X ; X = Y or Sc) in zirconia on carbon deposition in CH 4 and CH 4 /H 2 O environments was studied experimentally and via first-principles calculations. In the CH 4 environment, the apparent activation energy for the carbon deposition of Ni/ScSZ was lower than that of Ni/YSZ. SEM/EDS observation indicated the Ni/XSZ interface was key to elucidating the dopant-induced difference. To clarify the difference, the calculation presented two mechanisms: first, the vacancy in ScSZ rather than that in YSZ was readily moved to a neighboring site, thereby stabilizing the vacancy configuration after CH–CH bonding. Second, Ni was readily distorted in Ni/ScSZ at the specific vacancy configuration, thereby decreasing the forward activation energy. In CH 4 /H 2 O environment, the calculation showed larger dopant Y caused steric hindrance to prevent CH + O→CHO which was the sensitive reaction in the steam reforming. This explained lower reforming rate in Ni/YSZ than in Ni/ScSZ. • The apparent activation energy of Ni/ScSZ was lower than that of Ni/YSZ. • The Ni/XSZ interface structure was key to explaining the difference due to dopant. • Larger dopant Y caused steric hindrance to prevent CHO formation. [Display omitted] [ABSTRACT FROM AUTHOR]

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In order to repair a failed AlSiY coating on aeroengine turbine components, the AlSiY coating was stripped using a nitric acid-based removal reagent. The homogeneity of chemical stripping was evaluated and the stripping mechanism was clarified using first-principles calculations. The effects of hydrofluoric acid (HF) and chromium trioxide (CrO3) on the homogeneity of chemical stripping were investigated by calculating the electronic work functions (EWFs) of the stripped surfaces. The results showed that the stripped surfaces of the AlSiY coating exhibited a serrated appearance when it was etched by a single nitric acid solution, indicating severely inhomogeneous stripping. With the addition of HF and/or CrO3, the homogeneity of chemical stripping could be greatly improved, which was attributed to the increased EWF of the (200) surface and the decreased EWF of the (110) surface, causing the corrosion cathode to transition from the (110) surface to the (200) surface. The HF+CrO3+HNO3 mixed reagent was the optimal combination for the uniform stripping of the AlSiY coating, while the inner layer was not broken. The Al atoms on the surface could be preferentially removed due to the strong bonding with acid ions. The research method proposed in the present work will provide a new means to design chemical removal reagents. [ABSTRACT FROM AUTHOR]

In this study, we comprehensively explored the electronic structure and optical properties of Ni-doped Bi4O5Br2 through first-principles computational calculations. By calculating its electronic structure and band characteristics, we investigated the impact of Ni doping on the photocatalytic performance of Bi4O5Br2. The computational results indicated that Ni doping significantly altered the band structure of Bi4O5Br2, leading to a reduction in the band gap width. The band gap for undoped Bi4O5Br2 was 2.151 eV, whereas the Ni-doped system exhibited a smaller band gap, directly indicating its enhanced visible light absorption capacity and facilitating the effective separation of photo-generated electron–hole pairs. Through analysis of 2D charge density maps, we observed changes in chemical bonding induced by Ni doping. The shortening of Ni-O bonds suggested increased bond strength, consistent with the observed reduction in cell volume. These findings provide a theoretical foundation for understanding the mechanisms behind the enhanced photocatalytic hydrogen production performance in Ni-doped Bi4O5Br2, offering valuable insights for the design and optimization of highly efficient photocatalytic materials. [ABSTRACT FROM AUTHOR]

Context: This research focused on the theoretical investigation of transition metal carbonyls [M(CO)4] coordinated with terminal germanium chalcogenides complexes [M(CO)3GeX], where M represents Ni, Pd, and Pt and X represents O, S, Se, and Te labeled 1–15. While the notable complexes M(CO)4 (where M = Ni, Pd, Pt) numbered 1, 6, and 11 are of significance, substituting one of the CO ligands in 1, 6, and 11 with a GeX ligand (where X = O, S, Se, or Te) result in substituted complexes (2–5, 7–10, and 11–15). Substituting of the CO ligand slightly alters these bond angles. Specifically, the ∠CMC bond angles for [Ni] complexes range from 111.9° to 112.2°, for [Pd] complexes from 111.4° to 111.7°, and for [Pt] complexes from 112.4° to 112.8°. These findings indicate a minor deviation from the tetrahedral geometry due to the influence of the new GeX ligand. Similarly, there is a slight change in the geometry of the metal complexes, where the ∠GeMC angles for [Ni] complexes are between 106.7° and 106.9°, for [Pd] complexes between 107.2° and 107.5°, and for [Pt] complexes between 105.9° and 106.4°. Comparing among the substituted GeX complexes, those containing GeTe exhibit a higher natural bond orbital (NBO) contribution from the Ge atom compared to the M atom. Consequently, based on the above observations, it can be inferred that GeX acts as an effective sigma donor in contrast to carbonyl compounds. Results of energy decomposition analysis (EDA) for the M–CO bond in 1, 6, and 11 and for the M–GeX bond in the other [M(CO)3(GeX)] complexes where M = Ni, Pd and Pt. The percentage contribution of ΔEelstat and ΔEorb shows a relatively identical behavior for all ligands in case of each metal complexes. Methods: Density functional theory (DFT) calculations were conducted using the B3LYP/gen/6-31G*/LanL2DZ level of theory to examine transition metal carbonyls [M(CO)4] coordinated with terminal germanium chalcogenides complexes [M(CO)3GeX], where M represents Ni, Pd, and Pt, and X represents O, S, Se, and Te labeled 1–15 utilized through the use of Gaussian 09W and GaussView 6.0.16 software packages. Post-processing computational code such as multi-wave function was employed for results analysis and visualization. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the effect and mechanism of O atom single doping, Ce and O atoms co-doping on the interfacial microscopic behavior of brazed Ni-Cr/diamond. Design/methodology/approach: Using first-principles calculations, the embedding energy, work of separation, interfacial energy and electronic structures of Ni-Cr-O/diamond and Ni-Cr-O-Ce/diamond interface models were calculated. Then, the effect of Ce and O co-doping was experimentally verified through brazed diamond with CeO2-added Ni-Cr filler alloy. Findings: The results show that O single-doping reduces the interfacial bonding strength between Ni-Cr filler alloy and diamond but enhances its interfacial stability to some extent. However, the Ce and O co-doping simultaneously enhances the interfacial bonding strength and stability between Ni-Cr filler alloy and diamond. The in-situ formed Ce-O oxide at interface impedes the direct contact between diamond and Ni-Cr filler alloy, which weakens the catalytic effect of Ni element on diamond graphitization. It is experimentally found that the fine rod-shaped Cr3C2 and Cr7C3 carbides are generated on diamond surface brazed with CeO2-added Ni-Cr filler alloy. After grinding, the brazed diamond grits, brazed with CeO2-added Ni-Cr filler alloy, present few fracture and the percentage of intact diamond reaches 67.8%. Compared to pure Ni-Cr filler alloy, the brazed diamond with CeO2-added Ni-Cr filler alloy exhibit the better wear resistance and the slighter thermal damage. Originality/value: Using first-principles calculations, the effect of Ce and O atoms co-doping on the brazed diamond with Ni-Cr filler alloy is investigated, and the calculation results are verified experimentally. Through the first-principles calculations, the interface behavior and reaction mechanism between diamond and filler alloy can be well disclosed, and the composition of filler alloy can be optimized, which will be beneficial for synergistically realizing the enhanced interface bonding and reduced thermal damage of brazed diamond. [ABSTRACT FROM AUTHOR]

In order to explore the casting technology of a high–strength aluminum alloy, the effects of nickel on the solidified microstructure and tensile properties of a 7075 aluminum alloy were studied. 7075 aluminum alloys without nickel and with 0.6% and 1.2% nickel were prepared by a casting method. The results showed that the increase of Ni content in the 7075 alloys increased the liquidus temperatures, primary α (Al) grains were refined significantly, and the divorced eutectic structure was gradually formed among α (Al) grains with the preformation of the Al3Ni phase. In comparison, the 7075 alloy with 0.6% nickel content had less intergranular shrinkage porosity, and its elongation and ultimate tensile strength was enhanced 45% and 105% higher than those of the as-cast 7075 aluminum alloy, respectively. When the Ni content was increased to 1.2%, the eutectic phases of the alloy became much coarser compared to the other two alloys, and the mechanical properties obviously reduced too. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) are widely used as catalysts for overall water splitting due to their maximum utilization of surface active sites. However, until now, efficient SACs for water splitting are still lacking. Herein, a systematic screening of the overall water splitting performance of Fe, Co, and Ni atoms anchored on M2C, nitrogen modified M2C, and Fe and N co-modification M2C MXenes is performed by using first-principles calculations. The results show that Fe/Mo2C exhibits better hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances among the studied TM/Mo2C structures, with the corresponding value of ΔGH* and ηOER being 0.03 eV and 0.66 V, respectively. In addition, there is an obvious volcanic curve relationship between the d-band center (εd) of TM/M2C and the overpotential of the OER (ηOER). Low N doping concentrations (25%) can also adjust the HER and OER activity of M2C. Interestingly, N doping and Fe loading co-modification Mo2C (Fe/N-Mo2C) shows the best HER and OER properties among the studied TM/N-Mo2C structures, with the corresponding ΔGH* and ηOER being 0.01 eV and 0.39 V, respectively. The thermodynamics binding energy and dynamics simulation results reveal that TM/M2C and TM/N-M2C are dynamically stable at the reaction temperature. This work shows that Fe/N-Mo2C can be a potential catalyst for overall water splitting. [ABSTRACT FROM AUTHOR]

High energy ball milling of metallic powders leads to high reactivity in the milled mixture. The reaction is often faster and starts at a lower temperature. However, the mechanisms responsible for this high reactivity are not yet completely understood. The aim of this study is to evaluate one of the possible activating factors of this heightened reactivity: nano-scale mixing of the reagents. Molecular dynamics was used to analyze the role of an amorphous Ni–Al mixing layer, mimicking the powder microstructure after milling, between two Ni layers. The impact of temperature and stoichiometry was investigated in relation to the formation of the B 2 -NiAl intermetallic compound. At low temperatures, pre-mixing does not seem to slow down the diffusion of Ni atoms in an amorphous Al region. Homogeneous nucleation was observed in this peculiar milled microstructure. These two phenomena explain why the nano-scale mixing observed experimentally after high energy milling is indeed an activating factor in the reactivity of metallic systems such as Ni–Al. [ABSTRACT FROM AUTHOR]

The regularities of microstructure formation in samples of multiphase composites obtained by additive electron beam manufacturing on the basis of aluminum alloy ER4043 and nickel superalloy Udimet-500 have been studied. The results of the structure study show that a multicomponent structure is formed in the samples with the presence of Cr23C6 carbides, solid solutions based on aluminum -Al or silicon -Si, eutectics along the boundaries of dendrites, intermetallic phases Al3Ni, AlNi3, Al75Co22Ni3, and Al5Co, as well as carbides of complex composition AlCCr, Al8SiC7, of a different morphology. The formation of a number of intermetallic phases present in local areas of the samples was also distinguished. A large amount of solid phases leads to the formation of a material with high hardness and low ductility. The fracture of composite specimens under tension and compression is brittle, without revealing the stage of plastic flow. Tensile strength values are significantly reduced from the initial 142–164 MPa to 55–123 MPa. In compression, the tensile strength values increase to 490–570 MPa and 905–1200 MPa with the introduction of 5% and 10% nickel superalloy, respectively. An increase in the hardness and compressive strength of the surface layers results in an increase in the wear resistance of the specimens and a decrease in the coefficient of friction. [ABSTRACT FROM AUTHOR]

Fuel cell technology has developed due to diminishing dependence on fossil fuels and carbon footprint production. This work focuses on a nickel–aluminum bronze alloy as an anode produced by additive manufacturing as bulk and porous samples, studying the effect of designed porosity and thermal treatment on mechanical and chemical stability in molten carbonate (Li2CO3-K2CO3). Micrographs showed a typical morphology of the martensite phase for all samples in as-built conditions and a spheroid structure on the surface after the heat treatment, possibly revealing the formation of molten salt deposits and corrosion products. FE-SEM analysis of the bulk samples showed some pores with a diameter near 2–5 μm in the as-built condition, which varied between 100 and −1000 μm for the porous samples. After exposure, the cross-section images of porous samples revealed a film composed principally of Cu and Fe, Al, followed by a Ni-rich zone, whose thickness was approximately 1.5 µm, which depended on the porous design but was not influenced significantly by the heat treatment. Additionally, by incorporating porosity, the corrosion rate of NAB samples increased slightly. [ABSTRACT FROM AUTHOR]

Based on a series of the first-principles and experimental data, a new interatomic potential for the La-Al-Ni ternary system has been developed in the framework of an embedded-atom model using a force matching technique. With the optimized potential, the ground states of various elemental phases of La, Al, Ni, and La-Al-Ni intermetallic compounds are accurately reproduced. Also, the liquid dynamic behavior and glass forming ability of the La-Al-Ni system are validated, and the simulation results show great agreement with those calculated by ab initio molecular dynamic and related experimental data, indicating the reasonability and availability of our developed embedded-atom-method potential. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations of reactions in Al/Ni layered systems have been carried out under isothermal conditions for a wide range of temperatures and several system sizes. An embedded atom method potential, known to reasonably reproduce the phase behavior of Al/Ni, was employed. Simulations revealed reaction mechanisms involving an initial fast process and much slower more complex longer-time reactions. The initial reaction process consists of diffusion of Ni from the pure solid Ni phase into the molten Al phase, resulting in the formation of an Al-rich Al/Ni liquid. The initial reaction ends when the Al/Ni liquid becomes saturated in Ni and solid Al/Ni phases begin to form at the interfaces between the pure solid Ni phase and the Al/Ni liquid. The growth of these solid phases is intrinsically slow compared to the formation of the liquid and is further slowed by the need for Ni to diffuse through the growing interfacial Al/Ni solid phases. Analysis of the initial Al/Ni liquid forming process indicates Fickian behavior with the Ni diffusion coefficient exhibiting Arrhenius temperature dependence. The longer-time slow reaction process(es) resulting in the growth of Al/Ni solid phases do not lend themselves to detailed numerical analysis because of the complex dependence of the Ni transport on the detailed nature of the interfacial layers. [ABSTRACT FROM AUTHOR]

As part of extensive research on the properties of nickel-aluminum alloys, corrosion tests of sintered materials produced by the innovative HPHT/SPS (high pressure, high temperature/spark plasma sintering) method were performed in 0.1 molar H2SO4 acid. The hybrid, unique device used for this purpose (one of only two such devices operating in the world) is equipped with a Bridgman chamber, which allows heating with high-frequency pulsed current and sintering of powders under high pressure in the range of 4–8 GPa and at temperatures up to 2400 °C. Using this device for the production of materials contributes to the generation of new phases not obtainable by classical methods. In this article, the first test results obtained for the nickel-aluminum alloys never before produced by this method are discussed. Alloys containing 25 at.% Al, 37 at.% Al and 50 at.% Al were produced. The alloys were obtained by the combined effect of the pressure of 7 GPa and the temperature of 1200 °C generated by the pulsed current. The time of the sintering process was 60 s. The electrochemical tests, such as OCP (open circuit potential), polarization tests and EIS (electrochemical impedance spectroscopy), were carried out for the newly produced sinters and the results were compared with the reference materials, i.e., nickel and aluminum. The corrosion tests showed good corrosion resistance of the produced sinters, with corrosion rates of 0.091, 0.073 and 0.127 mm per year, respectively. It leaves no doubt that the good resistance of materials synthesized by powder metallurgy is due to the proper selection of the manufacturing process parameters, ensuring a high degree of material consolidation. This was further confirmed by the examinations of microstructure (optical microscopy and scanning electron microscopy) and the results of density tests (hydrostatic method). It has been shown that the obtained sinters were characterized by a compact, homogeneous and pore-free structure, though at the same time differentiated and multi-phase, while the densities of individual alloys reached a level close to the theoretical values. The Vickers hardness of the alloys was 334, 399 and 486 HV10, respectively. [ABSTRACT FROM AUTHOR]

Advanced high-temperature oxidation resistance is a crucial characteristic of metallic materials in porous burners. Extreme combustion conditions could lead to oxidation-affected erosion of porous media at a long-time period of burner operation. In this paper, we numerically simulated oxide scale growth at a porous radiant burner fabricated by Ni-Al intermetallic alloy using the combustion synthesis method, focusing on the structure degradation caused by periodic oxide scale spallation. A three-dimensional geometrical model of a porous intermetallic scaffold was obtained by scanning the porous burner using the X-ray CT technique. The surface erosion was modeled by the surface reconstruction based on calculated values of spalled oxide layer thickness. The simulation revealed that the submerged flame results in non-uniform distribution of the temperature at the solid surface. Such non-isothermal conditions lead to a two-times thicker oxide scale at the external surface of the burner. Thin struts of the intermetallic scaffold are prone to oxidation-affected erosion first, which forms discontinues and further fragmentation. The porous scaffold could lose about 50% of initial weight before fragmentation under conditions with intense oxide spallation. In such large structural degradation, the average flow velocity could reduce by a factor of 3, leading to changing of flame stabilization region. [ABSTRACT FROM AUTHOR]

High strength and ductile nickel aluminum bronze (NAB) alloys were produced by heavy warm rolling (HWR) and subsequent annealing at various temperatures. The effect of annealing temperatures ranging from 473 K to 1173 K (200 °C to 900 °C) on the microstructure, mechanical, and electrochemical properties of these HWRed NAB alloys was studied. The results show that the evolution of microstructure and mechanical behavior can be divided into three distinct stages with the increasing annealing temperature. When annealed below 500 °C (Stage A), the HWRed samples exhibit ultrahigh strength and good ductility. Such remarkable tensile properties are mainly attributed to the ultrafine α grains and nano k precipitates. Part of the α phase recrystallized, contributing to a further decrease in the average grain size. An ultrahigh ultimate strength of 1363 MPa and uniform elongation of 6.0 pct can be obtained when the alloy is annealed at 400 °C for 1 hour. When annealed at 600 °C and 700 °C (Stage B), a prominent strength–ductility combination with a yield strength of about 1000 MPa and an elongation of about 15 pct can be achieved, mainly due to the uniform ultrafine microstructures and the high-density annealing twins. Some nano k phases with grain size less than 20 nm precipitate dispersedly in α grains, which may also be a significant strengthening factor. When the temperature reaches above 800 °C (Stage C), the yield strength reduces dramatically, while the elongation and ultimate strength further increase. At this stage, the matrix transforms from single ultrafine α grains into a fine-grained (α + β′) duplex structure with high-density ultrafine annealing twins inside α grains. It is found that the mechanical properties of the HWRed and annealed alloys are greatly enhanced, while the electrochemical stability almost shows no deterioration compared with the undeformed coarse-grained alloys. This indicates that HWR and subsequent annealing is an effective strategy for preparing bulk NAB alloys with high performance. [ABSTRACT FROM AUTHOR]

In this work, the microstructure and tribological properties of coarse-grained nickel aluminum bronze (NAB) alloys with different ratios of α/β′ phases were studied at room temperature. For revealing the intrinsic tribology behavior, the hard SiC sanding disc with a microhardness of 2400∼2800 HV, almost 10 times higher than that of the NAB alloy, was selected as the counter material. The tribological behavior was investigated using multiscale characterization, including macroscale X-ray diffraction (XRD) and laser scanning confocal microscopy (LCM), microscale scanning electron microscopy (SEM), as well as nanoscale transmission electron microscopy (TEM). The findings reveal that abrasive wear predominates in these samples, with delamination, oxidation, and fatigue wear also present. Notably, the dual-phase alloy exhibits inferior wear resistance compared to the single-phase alloy, attributed to the alternating-wear process of the two phases. Additionally, we observed the in-situ formation of a nano oxide film during the friction process, highlighting its significant role in enhancing the wear resistance of NAB alloys through a self-lubricating effect. • Phase composition and microhardness are the two most important factors affecting the wear performance of the coarse-grained NAB alloys. • The dominant wear mechanism is abrasive wear, accompanied by delamination wear, oxidation wear, and fatigue wear. • A nano oxide film can be in-situ generated during the friction process, leading to the self-lubricating effect. • A mechanism of two-phase alternating wear that can accelerate the wear process has been revealed. [ABSTRACT FROM AUTHOR]

NiAl intermetallic formation occurs along the interfaces in the Ni/Al multilayer system during molecular dynamics simulations of deep (>50%) supercooling. The simulations begin with a crystalline solid solution at the Ni/Al interfaces that melts at 800 K, a supercooling of 56% of NiAl's simulated melting temperature (1800 K), and undergoes solid-state amorphization at 650 K, a supercooling of 64%. The intermetallic phase, NiAl, then forms at the interface from the melted/amorphous region through heterogeneous nucleation followed by growth in both lateral and normal directions. Upon nucleation, the intermetallic phase retains a fraction of the composition gradient present within the initial solid solution, and that fraction is always larger at 650 K, compared to 800 K, for the same initial composition gradient. Kinetics of the transformation follows the Johnson-Mehl-Avrami model, and an Avrami exponent of 0.5 was extracted at 800 K and 0.1 at 650 K. The NiAl formation is growth-controlled and the growth rate is found to increase with the decreasing initial composition gradient. Our finding supports a growth-competition mechanism of phase selection for interfacial reactions. [ABSTRACT FROM AUTHOR]

In this paper, we compare the composition fluctuations and interaction potentials of a good metallic glass former, Cu50Zr50, and a poor glass former, Ni50Al50. The Bhatia-Thornton correlation functions are calculated. Motivated by the observation of chemical ordering at the NiAl surface, we derive a new property, R ^ c n ( q ) , corresponding to the linear susceptibility of concentration to a perturbation in density. We present a direct comparison of the potentials for the two model alloys using a 2nd order density expansion, and establish that the one-body energy plays a crucial role in stabilizing the crystal relative to the liquid in both alloys but that the three-body contribution to the heat of fusion is significantly larger in NiAl than CuZr. [ABSTRACT FROM AUTHOR]

In this paper, we compare the composition fluctuations and interaction potentials of a good metallic glass former, Cu50Zr50, and a poor glass former, Ni50Al50. The Bhatia-Thornton correlation functions are calculated. Motivated by the observation of chemical ordering at the NiAl surface, we derive a new property, R ^ c n ( q ) , corresponding to the linear susceptibility of concentration to a perturbation in density. We present a direct comparison of the potentials for the two model alloys using a 2nd order density expansion, and establish that the one-body energy plays a crucial role in stabilizing the crystal relative to the liquid in both alloys but that the three-body contribution to the heat of fusion is significantly larger in NiAl than CuZr. [ABSTRACT FROM AUTHOR]

AlNi2Ti–Ti2Ni–NiTi intermetallic alloy consisting of AlNi2Ti primary dendrites and Ti2Ni–NiTi interdendritic phase was fabricated by vacuum arc melting process. Corrosion and wear behaviors of the alloy were characterized using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and wear tests. Electrochemical measurements indicated that the alloy exhibited an excellent corrosion resistance in 0.5 mol/L H2SO4 solutions with a high corrosion potential and wide passivation region (0–1.2 V) due to the formation of compact and protective passive films (TiO2 and Al2O3). Due to the high hardness and strong covalent bonding AlNi2Ti–Ti2Ni–NiTi alloys exhibit excellent wear resistance with a low friction coefficient and wear rate under dry sliding wear conditions. The dominant wear mechanisms of the alloy are friction stress-induced micro-fracture and tribo-oxidation. [ABSTRACT FROM AUTHOR]

The effect of nickel precursors and the temperature annealing to obtain intermetallic Ni3Sn2 alloy catalysts on its activity and selectivity in the selective hydrogenation of biomass-derived furfural (FFald) were investigated. Two types of nickel precursors (c.a., i) nickel metal (Ni°) derived from Raney®nickel and ii) nickel ion (Ni2+) derived from nickel chloride) were employed as the starting materials via hydrothermal at 423 K for 24 h followed by reduction with H2 at the elevated temperature of 573-873 K for 1.5 h. The physico-chemical properties of the intermetallic Ni3Sn2 were characterized by XRD, N2-, and H2-adsorption, ICP-AES, and NH3-TPD. The intermetallic Ni3Sn2 alloy catalysts, both bulk and supported, demonstrated high activity and selectivity towards hydrogenation of FFald. The activity and selectivity of γ-Al2O3 and AA-supported Ni3Sn2 alloy catalysts in the hydrogenation of FFald to furfuryl alcohol (FFalc) were maintained even after annealing at up to 873 K, but that of bulk Ni3Sn2 drastically dropped. Ni-Sn alloy catalysts which were obtained from Raney®Ni precursor showed more stable than that of nickel salts during hydrogenation of furfural to furfuryl alcohol. [ABSTRACT FROM AUTHOR]

Materials based on the NiAl-Cr-Mo system with zirconium oxide or aluminum-magnesium spinel nanoparticle small additions were obtained by spark plasma sintering. Thermodynamic modeling was carried out to predict the phase formation in the NiAl-Cr-Mo system and its change depending on temperature, considering the presence of a small amount of carbon in the system. The phase composition and microstructure of materials were studied. NiAl (B2) and CrMo phases were found in the sintered samples. Bending strength measurements at different temperatures shows that nanoparticles of insoluble additives lead to an increase in bending strength, especially at high temperatures. A fractographic analysis of the sample's fractures shows their hybrid nature and intercrystalline fracture, which is confirmed by the clearly visible matrix grains similar to cleavage. The maximum strength at 700 °C (475 MPa) was found for material with the addition of 0.1 wt.% zirconium oxide nanoparticles. In the study of internal friction, typical peaks of a nickel-aluminum alloy were found in the temperature ranges of 150–200 °C and 350–400 °C. [ABSTRACT FROM AUTHOR]

The objective of this study was to improve the corrosion resistance of an A535 alloy by removing intermetallics on the alloy surface by alkaline etching to improve the morphologies and properties of the anodic film that was sealed with different sealants. It was found that alkaline etching for 4 min was suitable for dissolving intermetallic particles and simultaneously providing sufficient roughness for the adhesion of an oxide film to the Al matrix. The effect of alkaline etching revealed that a decrease in the intermetallic fraction from 21% to 16% after etching for 2 and 4 min, respectively, corresponded to the increase in the surface roughness, thickness, and consistency of the anodic film. It was also demonstrated that the surface morphology of the anodic films after stearic acid sealing was more uniform and compact than that after nickel fluoride sealing. The electrochemical polarization curves and salt spray test proved that the alloy etched for 4 min and sealed with stearic acid had better corrosion resistance as compared with the aluminum alloy sealed with nickel fluoride. [ABSTRACT FROM AUTHOR]

The surface structures and compositions of Au-Rh bimetallic nanoclusters on an ordered thin film of Al2O3/NiAl(100) were investigated, primarily with infrared reflection absorption spectra and temperature-programmed desorption of CO as a probe molecule under ultrahigh-vacuum conditions and calculations based on density-functional theory. The bimetallic clusters were formed by sequential deposition of vapors of Au and Rh onto Al2O3/NiAl(100) at 300 K. Alloying in the clusters was active and proceeded toward a specific structure--a fcc phase, (100) orientation, and Rh core-Au shell structure, regardless of the order of metal deposition. For Au clusters incorporating deposited Rh, the Au atoms remained at the cluster surface through position exchange and became less coordinated; for deposition in reverse order, deposited Au simply decorated the surfaces of Rh clusters. Both adsorption energy and infrared absorption intensity were enhanced for CO on Au sites of the bimetallic clusters; both of them are associated with the bonding to Rh and also a decreased coordination number of CO-binding Au. These enhancements can thus serve as a fingerprint for alloying and atomic inter-diffusion in similar bimetallic systems. [ABSTRACT FROM AUTHOR]

To reduce the cobalt (Co) content in lithium-ion batteries, Ni-rich (high-Ni) lithium nickel manganese cobalt oxides (NMC) are pursued as one of the next-generation cathode materials. However, there is still debate on the crystal and electronic structures of the baseline, LiNiO 2. Density Functional Theory (DFT) calculations were performed to provide a theoretical understanding of Ni-rich NMC. First, it was found that the commonly used R 3 ¯ m structure for LiNiO 2 is metallic, contrary to the experimentally reported mix-conducting behavior. Among the four different space groups, R 3 ¯ m , C2/m , P2 1 /c , and P2/c , P2/c with charge disproportionation of Ni2+ and Ni4+ is the most energetically stable and semiconducting structure of LiNiO 2. Therefore, the atomic structures of representative Ni-rich NMC were built by partially replacing Ni with Co or Mn in the P2/c LiNiO 2 to form Li x Ni y Mn z Co 1-y-z O 2. In the fully lithiated (x = 1.0) high Ni content NMC (y > 0.5), the oxidation state of all Mn ions becomes 4+, while Co ions still maintain 3+, and part of the Ni ions become 2+ to compensate for the charge. Upon delithiation, the local environment shows more variation of the charge states on the transition metal (TM) ions. The average oxidation on each TM follows a sequence of losing electrons that starts from Ni2+ to Ni3+, then oxidizing Ni3+ and Co3+, while Mn4+ remains electrochemically inactive till x = 0. A general relationship for the oxidation state change in each TM as a function of x and y is derived and shows agreement with both modeling and experimental data. • The commonly used R 3 ¯ m symmetry (for LiCoO 2) is not the correct for LiNiO 2. • Built representative structures for Ni-rich Li x Ni y Mn z Co 1-y-z O 2 cathode materials. • Revealed the structure and redox mechanisms for Li x Ni y Mn z Co 1-y-z O 2. • Derived a general relationship for oxidation state change as a function of SOC. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) transition-metal sulfide and single-atom catalysts are attractive materials and their excellent performance play an important role in various fields. In this study, we investigate the sensing properties of Ni-decorated MoS 2 towards dopamine (DA) molecule by using first-principles method. Ni is identified as the primary anchoring point for the DA molecule. We further examine the synergistic effect of intrinsic defects on the system and find that they significantly influence the adsorption behavior. The presence of a Mo defect leads to a 7 % increase in the adsorption energy compared to the scenario without any defects. By applying an in-plane voltage to these models, the I–V curve and conductivity are calculated to simulate the experimental detectability. The detection sensitivity can be significantly improved by suitable in-plane voltage. By applying a back-gate electric field, the influence of interface charge transfer on the adsorption characteristics of DA is investigated, and the back-gate electric field brings a significant enhancement of the adsorption energy, with an impressive increase up to 34 %. This study provides valuable insights into the sensing properties of DA by assessing the adsorption energy and suggests possible avenues for improving the detection sensitivity. The Ni-decorated MoS 2 with synergetic intrinsic defects holds outstanding sensing properties towards dopamine molecule. [Display omitted] • The sensing properties of Ni-decorated MoS 2 towards dopamine are investigated. • The presence of a Mo defect leads to a 7 % increase in the adsorption energy. • The detection sensitivity can be improved by suitable in-plane voltage. • The back-gate electric field brings a significant enhancement of adsorption energy. [ABSTRACT FROM AUTHOR]

In this paper, a Z-type heterojunction is formed between BiOI and Ni doped MoS 2 by hydrothermal and microwave-assisted methods. The composites were characterised by a range of characterisation methods. The test results show that the formation of heterojunction can reduce the forbidden bandwidth of the material and improve the absorption of visible light, and the photocatalytic performance can be improved. The degradation efficiency of 5 % BiOI/Ni 0.05 Mo 0.95 S 2 against 150 mg/L rhodamine B was 95.08 % in 300 min. The analysis of first-principles calculations reveals that BiOI will hybridise with Ni 0.05 Mo 0.95 S 2 at the energy level, leading to a decrease in the forbidden bandwidth of the composite. The difference in the figure of merit of the two materials favours the reduction of the photogenerated carrier complexation rate, which is conducive to the enhancement of the photocatalytic performance. This research uses impurity energy levels and heterojunctions together on catalytic materials to improve their catalytic properties which has far-reaching implications for future research on environmental issues. BiOI was chosen to form heterojunctions by microwave-assisted compounding with Ni 0.05 Mo 0.95 S 2 to achieve degradation of high rhodamine B concentrations under visible light. [Display omitted] • BiOI/Ni0.05Mo0.95S2 composites were prepared by the microwave-assisted method. • In 300 min of 150 mg/L RhB, the degradation efficiency of 5% BiOI/Ni 0.05 Mo 0.95 S 2 was 95.08%, and the reaction rate constant was 1.095 times that of Ni 0.05 Mo 0.95 S 2. • Trap tests on the composites indicate that the main reactive group in the photocatalytic degradation of RhB is h+. • First-principles calculations have shown that the formation of heterostructures of BiOI and Ni 0.05 Mo 0.95 S 2 can facilitate charge transfer and favorably improve photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Electrochemical fluorination in anhydrous HF, also known as the Simons process, is a widely used industrial method for fluorination of organic compounds. Its mechanism, being not so well understood, has long been debated and is believed to involve higher valent nickel fluorides formed on the nickel-plated anode during the process. One of these is speculated to be Ni2F5, which was previously reported in the literature and assigned via infrared spectroscopy, but its crystal structure is not yet known. We have identified known crystal structures of compounds with similar stoichiometries as Ni2F5 and utilized them as a starting point for our periodic DFT investigations, applying the PBE+U method. Ni2F5 as the most stable polymorph was found to be of the same crystal structure as another mixed valent fluoride, Cr2F5. The calculated lattice parameters are a = 7.24 Å, b = 7.40 Å, c = 7.08 Å and β = 118.9° with an antiferromagnetic ordering of the nickel magnetic moments. [ABSTRACT FROM AUTHOR]

The purpose of this study is to compare the performance of specific composite propellers with different ply angles from a cavitation inception speed (CIS) perspective. Composite propellers have a relatively large deformation compared to existing propellers manufactured using nickel aluminum bronze alloys. Therefore, it is necessary to understand the correlation between the stacking method of the composite materials and the propeller performance in order to design composite propellers that provide sufficient strength and generate the desired deformation. In addition, in the case of composite propellers, the deformation is closely related to the CIS because it can delay or accelerate the occurrence of tip vortex cavitation (TVC). Fluid-structure interaction (FSI) analysis of the model-scale composite propellers is performed using a coupled computational fluid dynamics (CFD)-finite element method (FEM) to examine the influence of the lamination direction on the deformation of the composite propeller. Finally, a hydroacoustic analysis of the noise generated and propagated by a composite propeller in non-cavitating and cavitating flows is conducted. The study found that some deformed parameters of the propeller affect the performance, the deformation of the composite propeller itself has no significant effect on the sound pressure level, and the volume change of cavitation has a decisive effect on the variation of the sound pressure level radiated from the composite propeller. These results can improve the feasibility, conceptual design, performance, and manufacturing methods for composite propellers. [ABSTRACT FROM AUTHOR]

In view of the large field of industrial application of bronze alloys, it becomes essential to carry out detailed metallurgical studies seeking the development of these alloys, specifically nickel-aluminum bronze, and one of the main technological fronts in which bronze is inserted is in aerospace applications, which require specific mechanical properties for the engineering material to support the efforts involved. One of the possibilities of reaching the properties is through the imposition of the variables present in the heat treatment, which influences the microstructure, due to the fact that bronze has martensitic transformation represented by β phase, and, consequently, on the mechanical behavior of the material. The objective of this work is to show the relationship between hardening by quenching, with subsequent tempering, and the mechanical properties generated in the aerospace bronze UNS C63000. The results show that the score in the order of 785, 835 and 885 °C followed by sudden cooling in water promotes an increase in the mechanical results, however, it is noted a gradual reduction in the percentage of α phase. [ABSTRACT FROM AUTHOR]

Nickel-aluminum bronze (NAB) alloys are widely used in hydraulic and pumping bodies due to their suitable mechanical properties and corrosion resistance. However, the tribological performance of these materials needs to be improved. In this study, the WC-10Co-4Cr, and Colmonoy-6 coatings were applied on a NAB alloy using high-velocity oxy-fuel (HVOF) spraying technique to enhance the corrosion and wear performance of the NAB substrate. The XRD phase analysis evidenced the dominant presence of the WC and W2C phases in the WC-10Co-4Cr coating and the Ni2Cr3 and Si2B3 compounds in the Colmonoy-6 coating. Morphological and surface analysis showed the formation of the coatings with roughness values of Ra = 4.9 ± 0.9 µm for Colmonoy-6 and Ra = 6.8 ± 1.1 µm for WC-10Co-4Cr coatings. The electrochemical measurement in a 3.5 wt.% NaCl solution revealed that applying WC-10Co-4Cr and Colmonoy-6 HVOF coatings improved the corrosion resistance of the NAB substrate by one order of magnitude. This improvement was more significant for Colmonoy-6 coating due to the presence of electrochemically nobler compounds containing Cr and Ni. Wear measurements obtained by pin-on-disk wear test and morphological analysis of the worn path showed the lowest friction coefficient and highest wear resistance for the WC-10Co-4Cr coating followed by Colmonoy-6 coating. The superior wear performance of the WC-10Co-4Cr coating was attributed to its comprehensive mechanical properties with a Vickers hardness of 1152 ± 25 HV30, while the hardness for Colmonoy-6 and NAB substate was 789 ± 65 and 164 ± 5 HV30, respectively. [ABSTRACT FROM AUTHOR]

Ni50Al50 alloy sample prepared by compacting the powdered alloys at 8 Ton Pressure and Sintered at 750°c for 45 Minutes. The magnetics structural properties and Phase analysis were investigated. Xray diffraction(XRD), Scanning electron microscopy (SEM), Elements dispersive spectroscopy (EDS) and Vibrating sample magnetometer(VSM) for change in magnetic properties were determined as methods for characterization of produced samples. The results of this alloy show that cubic fcc structure from reflections of (111), (200) and (220). The magnetic results showed that the Saturation Magnetizations (Ms) of the composite alloy substantially decrease. The microhardness values of the alloy was observed that increased with increasing Aluminum addition. [ABSTRACT FROM AUTHOR]

Crystal growth of the glass-forming CuZr alloy is shown to be abnormally slow, which suggests a new method to identify the good glass-forming alloys. The crystal growth of elemental Cu, Pd and binary NiAl, CuZr alloys is systematically studied with the aid of molecular dynamics simulations. The temperature dependence of the growth velocity indicates the different growth mechanisms between the elemental and the alloy systems. The high-speed growth featuring the elemental metals is dominated by the non-activated collision between liquid-like atoms and interface, and the low-speed growth for NiAl and CuZr is determined by the diffusion across the interface. We find that, in contrast to Cu, Pd, and NiAl, a strong stress layering arisen from the density and the local order layering forms in front of the liquid-crystal interface of CuZr alloy, which causes a slow diffusion zone. The formation of the slow diffusion zone suppresses the interface moving, resulting in much small growth velocity of CuZr alloy. We provide a direct evidence of this explanation by applying the compressive stress normal to the interface. The compression is shown to boost the stress layering in CuZr significantly, correspondingly enhancing the slow diffusion zone, and eventually slowing down the crystal growth of CuZr alloy immediately. In contrast, the growth of Cu, Pd, and NiAl is increased by the compression because the low diffusion zones in them are never well developed. [ABSTRACT FROM AUTHOR]

Nanoscale layers of nickel and aluminum can mix rapidly to produce runaway reactions. While self-propagating high temperature synthesis reactions have been observed for decades, the solid-state ignition of these reactions has been challenging to study. Particularly elusive is characterization of the low-temperature chemical mixing that occurs just prior to the ignition of the runaway reaction. Characterization can be challenging due to inhomogeneous microstructures, uncontrollable heat losses, and the nonuniform distribution of heat throughout the material prior to ignition. To reduce the impact of these variables, we heat multilayered Ni/Al foils in a highly uniform manner and report ignition temperatures as low as 245 °C for heating rates ranging from 2000 °C/s to 50 000 °C/s. Igniting in this way reveals that there are four stages before the reaction is complete: heating to an ignition temperature, low temperature solid-state mixing, a separate high temperature solid-state mixing, and liquid-state mixing. Multiple bilayer spacings, heating rates, and heating times are compared to show that the ignition temperature is a function of the bilayer spacing. A symmetric numerical diffusion model is used to show that there is very little chemical mixing in the first 10 ms of heating but significant mixing after 50 ms. These predictions suggest that ignition temperatures should increase for the slowest heating rates but this trend could not be identified clearly. The modeling was also used to examine the kinetic parameters governing the early stages of solid-state diffusion and suggest that grain boundary diffusion is dominant. [ABSTRACT FROM AUTHOR]