Search Results (107)

Grey cast iron brake discs remain standard in automotive braking systems due to their favourable thermal conductivity and mechanical strength. However, increasingly stringent environmental regulations, including Euro 7, necessitate enhanced surface durability to reduce particulate emissions and mitigate corrosion-related degradation. In this context, laser metal deposition (LMD) offers a promising route to engineer wear-resistant coating systems with tailored microstructures. This study investigates phase formation and microstructural evolution in a 316L/430L-WC multilayer coating deposited on grey cast iron (GJL) brake discs and subjected to brake-shock testing to replicate thermomechanical load cycles representative of real braking conditions. X-ray diffraction (XRD) performed on the interlayer region between the 316L and 430L-WC layers revealed clear evidence of σ-phase formation, indicating intermetallic transformations facilitated by thermal cycling. Microstructural characterization using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) identified localized enrichment of Cr- and Fe-rich regions that support the XRD-based interpretation of σ-phase development. These results provide insights into phase transformations and elemental diffusion in LMD-fabricated brake-disc coatings. The findings advance the understanding of thermally induced transformations in multilayer steel systems and support the optimization of LMD coatings for high-temperature and wear-intensive applications through advanced analytical evaluation. Full article

The subject of this study is the electrochemical synthesis of samarium–cobalt (Sm-Co) alloy coatings on a copper substrate from aqueous solutions using chronoamperometric methods. The study focused on assessing the effect of ecological complexing agents—L-arginine and glycine—on the deposition kinetics and quality of the deposits obtained within a potential range of −1.1 V to −1.8 V vs. Ag/AgCl. Morphological analyses indicated that the type of amino acid used determines the layer growth mechanism. It was found that exceeding the potential of −1.4 V results in a rapid increase in samarium content in the alloy, reaching maximum values of 29 at.% for the system with L-arginine and 35 at.% for the system with glycine at a potential of −1.8 V. X-ray Diffraction (XRD) structural studies confirmed the successful synthesis of the Co_8.5Sm intermetallic phase directly by electrodeposition, while X-ray Photoelectron Spectroscopy (XPS) analyses indicated the presence of oxides and hydroxides on the deposit surface. Despite obtaining a high samarium content, it was observed that intense hydrogen co-evolution at low potential leads to a decrease in current efficiency and the formation of internal stresses and cracks in the structure of the coatings. Full article

This study investigates the elastic anisotropy and thermodynamic properties of the L1₂-type ScAl₃ phase under extreme conditions (0–1500 K and 0–50 GPa) using first-principles calculations. The elastic constants were determined using a precise stress–strain method, with polycrystalline moduli derived via the Voigt–Reuss–Hill (VRH) approximation. A systematic analysis was conducted to characterize the elastic anisotropy of Young’s modulus, shear modulus, and Poisson’s ratio. Results demonstrate that ScAl₃ is mechanically stable and exhibits near-perfect elastic isotropy (A^U = 0.0001). Thermodynamic analysis via the quasi-harmonic Debye–Grüneisen model reveals that the phase maintains its structural integrity and significant heat resistance up to 1500 K, despite thermal softening. These findings provide theoretical insights into the physical nature of ScAl₃ intermetallics and offer quantitative guidance for the design and thermal treatment of Sc-reinforced aluminum alloys in high-temperature aerospace applications due to their superior combination of strength and toughness. Full article

Pt-based intermetallics are high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) in proton exchange membrane water electrolysis (PEMWE). However, the synthesis of intermetallics usually relies on high-temperature annealing, which easily induces particle agglomeration and limits the improvement of catalytic performance. In this study, a synergistic strategy of spatial confinement and ordered structure regulation is adopted, and indene-derived mesoporous carbon (IMC) is used as the support to controllably synthesize the intermetallic Pt₃Fe catalyst. The IMC support can anchor and spatially confine nanoparticles, thereby preventing particle sintering and agglomeration during high-temperature annealing. In 0.5 mol·L⁻¹ H₂SO₄ electrolytes, the catalyst exhibits excellent catalytic performance: it achieves an overpotential of only 19.1 mV at a current density of 10 mA·cm⁻², which is 9.4 mV lower than that of commercial Pt/C; its mass activity reaches 2.76 A·mg_Pt⁻¹, 8 times that of commercial Pt/C. Chronopotentiometry measurements show negligible potential variation after 190 h of operation at 10 mA·cm⁻². This strategy suppresses particle agglomeration through the spatial confinement effect of IMC and modulates electronic states via the ordered structure, providing a practical route for the scalable preparation of low-cost, highly active and high-stability Pt-based intermetallics for PEMWE applications. Full article

Pt–transition metal intermetallic compounds have been recognized as promising catalysts for oxygen reduction reaction (ORR). However, further enhancing the activity and durability of this kind of catalyst is still necessary. Herein, we report a novel L1₀-type PtFe intermetallic nanoalloy with the partial substitution of Fe sites by La as a highly active and stable catalyst towards ORR. This new intermetallic nanoalloy retains an ordered structure after the incorporation of La confirmed by XRD, XPS and TEM results and the ordered PtFe_0.5La_0.5 nanoparticles are embedded in porous carbon (L1₀-PtFe_0.5La_0.5@C) in very uniform particle size of around 2 nm. This L1₀-PtFe_0.5La_0.5@C catalyst exhibits a half-wave potential of 933 mV, which is about 12 mV and 70 mV higher than those of L1₀-PtFe@C and commercial Pt/C catalysts, respectively. Moreover, it also achieves an enhanced mass activity of 0.79 A mg_Pt⁻¹ at 0.90 V, which outperforms the performance of commercial Pt/C (0.10 A mg_Pt⁻¹). In addition, it also shows excellent stability with only 3 mV negative shift in half-wave potential after 20k CV cycles of accelerated durability testing. This high activity and stability may be attributed to the incorporation of La in the PtFe lattice, which induces the formation of a compressively strained Pt overlayer in acidic media which not only tunes the surface strain of Pt sites but also possesses robust resistance to the dissolution of Fe and La. This work also provides a new direction for the development of Pt-based intermetallic catalysts for efficient catalysis applications. Full article

Binder Jetting 3D Printing (BJ3DP) offers an effective pathway for the rapid fabrication of complex high-entropy alloy (HEA) components. In this study, the macroscopic characteristics, microstructural evolution and mechanical properties of Al_0.5Cr_0.9FeNi_2.5V_0.2 HEA green parts prepared via BJ3DP were investigated under various sintering conditions. Results showed that the relative density of the sintered parts increased significantly with temperature, transitioning from a low density (<90%) at 1300–1330 °C to near-fully dense (~98%) at 1340–1350 °C. Consequently, the mechanical properties were remarkably improved. The yield strength (σ_0.2) increased from 300 MPa to 710 MPa (a 136% increase), and the ultimate tensile strength (σ_b) rose from 310 MPa to 780 MPa (a 148% increase) as sintering temperature rose from 1300 °C to 1350 °C. Microstructural analysis revealed that at lower sintering temperatures, the alloy exhibited high porosity and a non-coherent structure composed of an FCC matrix and Cr-rich BCC phase, with Al/Ni intermetallic compounds distributed around pores. Conversely, at the final sintering stage, pore closure was achieved, and a coherent structure consisting of an FCC matrix and scale-like L1₂ precipitates was formed. Optimal mechanical properties (tensile strength ≥ 700 MPa) were achieved when sintering at 1340 °C, primarily attributed to densification and precipitation strengthening. Full article

The study investigates the microstructure evolution in the stir zone produced by the friction stir processing (FSP) of a heat-treated microalloyed Al-Mn-Cu alloy in the area subjected to the highest temperature, strain, and strain rate. The samples were studied using electron microscopy and atom probe tomography (APT) to obtain structural and chemical information from the macro to the nano scale. FSP refines the dendritic Al-rich solid solution grains through dynamic recrystallisation in the range of a few micrometres. The primary intermetallic phases were dispersed to the particles in the 0.5–3 µm range and transformed mainly into a more stable τ₁-Al₂₉Mn₆Cu₄ phase. The fraction of dispersed particles after FSP increased due to the precipitation from the solid solution during cooling. The nanoscale quasicrystalline precipitates in the matrix, formed upon heat treatment, dissolved entirely during FSP, while the strong coarsening of the L1₂ precipitates occurred due to high temperatures in the stir zone. After FSP, the hardness of the stir zone was nearly identical for specimens in the as-cast and heat-treated conditions. Full article

This work investigates the structural evolution and electrocatalytic activity of the amorphous metal alloy Al₈₇Y₄Gd₁Ni₄Fe₄ during short-term annealing and its effect on the kinetics of the hydrogen evolution reaction (HER) in 1 M KOH. It is shown that a 5 min heat treatment at 647 ± 2 K initiates controlled nanocrystallisation with the formation of AlFe₂Ni, GdFe₂ and Al(X) (X = Gd, Ni, Y, Fe) phases, which are uniformly dispersed in the amorphous matrix. According to XRD, DSC and HRTEM data, it was established that the formation of intermetallic nanodomains leads to a decrease in charge transfer energy barriers and the appearance of additional active centres of H* adsorption. Electrochemical studies have shown an increase in cathode current density, an increase in i₀ by 2–3 orders of magnitude, and a decrease in R_ct after annealing, confirming the improvement in HER kinetics. Potentiostatic tests showed an increase in the volumetric hydrogen evolution rate from 35.1 to 106.0 mL/(g·min) during the first immersion and up to 217.9 mL/(g·min) during reuse. SEM/EDS analysis revealed surface reconstruction and Ni enrichment after HER, which contributes to the acceleration of the H* recombination stage. The synergy of the amorphous matrix and nanophases ensures high electrocatalytic activity and stability of the system, making annealed AMA a promising low-cost catalyst for alkaline hydrogen evolution. Full article

Cavitation erosion is a critical problem for many engineering components, such as ship propellers, diesel engine exhaust valves, cylinder liners, pump impeller blades, hydraulic turbines, and bearings, which are exposed to high-velocity flowing fluids or to vibratory fluid motion. It represents a mechanical degradation of the surface caused by the continuous collapse of bubbles in the surrounding liquid, which seriously affects flow efficiency and component service life, increasing maintenance frequency and refurbishment costs. The intensity and evolution of the cavitation erosion phenomenon depend on the hydrodynamic conditions to which the component surface is exposed, the properties of the liquid, and the judicious selection of the most suitable material. This paper aims to modify the microstructure of a Ni-based superalloy by applying recrystallization annealing heat treatment in order to obtain surfaces resistant to cavitation erosion for components that handle fluids under local pressure fluctuations. Experimental tests are carried out using a vibratory apparatus with piezoceramic crystals operating at a frequency of 20 kHz and an amplitude of 50 µm. The cavitation erosion performance of the Ni-based superalloy INCONEL 625, heat treated by recrystallization annealing, are compared with that of austenitic stainless steel AISI 316L subjected to solution treatment. For both metallic alloys, based on mass loss measurements, the characteristic time-dependent curves of the mean cumulative erosion penetration depth, MDE(t), and the mean erosion rate, MDER(t), are determined. The comparison of these curves and of the parameters defined and recommended by the ASTM G32 standard demonstrates that, for the Inconel 625 superalloy, resistance to cavitation erosion increases by 77–81% compared to that of AISI 316L austenitic stainless steel. X-ray diffraction analyses (XRD) show that, in the microstructure of the Inconel 625 superalloy, in addition to austenite, MC-type carbides, M₂₃C₆ carbides, and intermetallic phases γ″ = Ni₃(Nb, Al, Ti) and δ = Ni₃(Nb, Mo) are also present. Full article

With the wide application of Ni-Al high-temperature materials, the research on their performance has increasingly attracted attention. To further advance the development of Ni-Al high-temperature materials, it is necessary to conduct an in-depth analysis of the brittleness mechanism of Ni-Al intermetallic compounds and elucidate the fundamental nature of their brittleness. In this study, the tensile mechanical behavior and microscopic mechanism of single crystals NiAl (B2) and Ni₃Al (L1₂) at different temperatures were systematically studied by molecular dynamics simulations. It is revealed that although the mechanical properties of both NiAl and Ni₃Al degrade with increasing temperature, their deformation mechanisms exhibit fundamental differences. The high-temperature strength of NiAl is attributed to stable plastic flow dominated by 1/2 <111> screw dislocation. The early softening of Ni₃Al is associated with the formation of stacking fault formation, the phase transition to the HCP, and the slip of various incomplete dislocations (e.g., 1/6 <112> Shockley dislocation). Atomic strain analysis shows that regions of high strain exhibit a strong spatial correlation with the phase-transformed domains. This study reveals the distinct deformation mechanism of the two alloy phases at the atomic scale, providing a key theoretical basis for the rational selection of Ni-Al alloy in specific high-temperature applications. Full article

The microstructure of the Ti-Al binary system is an area of great interest, as it affects material properties and plasticity. Phase transformations induce microstructural changes; therefore, accurately modeling the phase transformations of the Ti-Al system is necessary to describe plasticity. Interatomic potentials can be a powerful tool to model how materials behave; however, existing potentials lack accuracy in certain aspects. While classical potentials like the Modified Embedded Atom Method (MEAM) perform adequately for modeling a dilute Al solute within Ti’s $\alpha$ phase, they struggle with accurately predicting plasticity. In particular, they struggle with stacking fault energies in intermetallics and to some extent elastic properties. This hinders their effectiveness in investigating the plastic behavior of formed intermetallics in Ti-Al alloys. Classical potentials also fail to predict the $\alpha$-to-$\beta$ phase boundary. Existing machine learning (ML) potentials reproduce the properties of formed intermetallics with density functional theory (DFT) but do not accurately capture the $\alpha$-to-$\beta$ or $\alpha$-to-D0₁₉ phase boundaries. This work uses a rapid artificial neural network (RANN) framework to produce a neural network potential for the Ti-Al binary system. This potential is capable of reproducing the Ti-Al binary phase diagram up to 30% Al concentration. The present interatomic potential ensures stability and allows results near the accuracy of DFT. Using Monte Carlo simulations, the RANN potential accurately predicts the $\alpha$-to-$\beta$ and $\alpha$-to-D0₁₉ phase transitions. The current potential also exhibits accurate elastic constants and stacking fault energies for the L1₀ and D0₁₉ phases. Full article

The interfacial behavior between lattice reinforcement and aluminum matrix plays an important role in determining the mechanical and tribological properties of lattice-reinforced aluminum matrix composites. In this study, 316L lattices with different aspect ratios were prepared by laser powder bed elting (LPBF) technology, and LY12 aluminum alloy was infiltrated under vacuum conditions. The effects of lattice aspect ratio on the interfacial reaction, microstructure, hardness, compressive strength, and wear resistance of the composites were systematically studied. First-principles calculations show that FeAl₂ and FeAl₃ intermetallic compounds are preferentially formed at the interface, showing good thermodynamic stability and mechanical properties. The microstructure analysis shows that the increase in aspect ratio promotes the formation of coarse FeAl₃ phase and network AlCu, while a too-large aspect ratio leads to the instability of microstructure and the generation of microcracks. When the lattice constant is 10 mm and the diameter of the support is 1 mm (BCC-10-1), the composite material has the best wear resistance, and the specific wear rate is 3.07 × 10⁻⁴ mm³/(N·m). These findings provide valuable insights into the design of high-performance lattice-reinforced aluminum matrix composites with customized interface properties. Full article

Graphene oxide (GO) is characterized by hydrophilic edges and a more hydrophobic planar/basic skeleton, which makes it has potential applications in the field of corrosion. But its hydrophobicity hinders its co-deposition behavior in the electrolyte. To improve the corrosion resistance of copper-based substrate, this article designs and successfully prepares a nickel/chromium graphene oxide (NiCr-GO) composite coating. The paper studied the influence and mechanism of GO addition on the microstructure and corrosion resistance of the coating. The results indicate that a crack network and nodular structure have formed on the surface of the coating. The coatings with different GO contents are composed of nickel, chromium single-phase, and Cr₂Ni₃ inter-metallic compounds, and the grain size does not significantly change. With the increase in GO, the corrosion resistance of the composite coating is enhanced, and the optimal GO addition amount is 0.750 g/L. GO chips may form physical barriers in the crystal structure defects of the coating, or passive films on the material surface. This dual mechanism is the fundamental reason for improving the corrosion resistance of NiCr-GO. Full article

This study addresses the challenge of low-temperature synthesis of the high-performance L1₀ Fe-Pt intermetallic phase, which is critical for applications in ultra-high-density data storage and advanced magnetic devices. We demonstrate that the choice of iron precursor is a decisive factor in directing the phase composition and thermal evolution of Fe-Pt nanostructures, ultimately determining their suitability as functional composite materials. Fe-Pt systems were synthesized from aqueous solutions using platinum(IV) chloric acid (H₂PtCl₆) with either iron(III) ammonium sulfate (NH₄Fe(SO₄)₂) or iron(II) sulfate (FeSO₄). Comprehensive characterization using X-ray diffraction and high-resolution transmission electron microscopy revealed distinct composite formations. The iron(III) precursor yielded homogeneous, thermally stable nanocomposites: as-synthesized nanoparticles formed a Pt-based FCC solid solution (~5 nm), which upon annealing at 500 °C transformed into a biphasic nanocomposite of FCC solid solution and an L1₂ Fe₂₁Pt₇₉ intermetallic phase with minimal grain growth (~7 nm). In stark contrast, the system derived from iron(II) sulfate resulted in a heterogeneous composite of 4 nm Pt nanoparticles, an FCC solid solution, and discrete 1–3 nm Fe nanoparticles with L1₂-ordered FePt₃ domains. Annealing this heterogeneous mixture caused phase segregation, forming significantly coarsened Pt-rich crystals (~30 nm) that were approximately 4–6 times larger than the crystallites in the annealed homogeneous composite, with negligible Fe incorporation. Our findings establish that precursor chemistry dictates the initial nanocomposite architecture, which in turn controls the pathway and success of low-temperature intermetallic phase formation. This work provides a crucial design principle for fabricating tailored Fe-Pt composite nanomaterials, moving beyond simple alloys to engineered multiphase systems for practical application. Full article

Additively manufactured maraging steel components often require surface engineering to achieve superior wear resistance for demanding industrial applications. This study investigates 18Ni300 maraging steel manufactured by Laser Powder Bed Fusion (L-PBF), comparing non-aged and pre-aged (480 °C × 6 h) specimens to systematically analyze the effects of nitriding duration (0 h, 24 h, 48 h, 60 h) on nitride layer microstructure, hardness, and wear resistance. Results show that the non-aged specimen, with its supersaturated solid solution matrix, exhibits slower nitride layer growth; a thin, dense nitride layer formed after 24 h of nitriding minimizes the wear depth (−9.043 μm) for optimal friction reduction. In the pre-aged specimen, matrix refinement, through intermetallic compound precipitation, enables a 211 μm nitride layer to form after 48 h of nitriding, elevating surface hardness to 650 HV, and creating a gradient structure (“high-hardness surface + strengthened matrix”), which yields the narrowest and shallowest wear scars and superior wear resistance. The experiments demonstrate that nitriding processes must align with matrix states; 24 h nitriding suits non-aged steel, while 48 h is optimal for aged steel, providing critical guidance for optimizing surface strengthening in additively manufactured 18Ni300 steel. Full article