Alloy Research Articles

Advanced Ir-Based Alloy Electrocatalysts for Proton Exchange Membrane Water Electrolyzers.

Proton exchange membrane water electrolyzer (PEMWE) coupled with renewable energy to produce hydrogen is an important part of clean energy acquisition in the future. However, the slow kinetics of the oxygen evolution reaction (OER) hinder the large-scale application of PEM water electrolysis technology. To deal with the problems existing in the PEM electrolyzer and improve the electrolysis efficiency, substantial efforts are invested in the development of cost-effective and stable electrocatalysts. Within this scenario, the different OER reaction mechanisms are first discussed here. Based on the in-depth understanding of the reaction mechanism, the research progress of low-iridium noble metal alloys is reviewed from the aspects of special effects, design strategies, reaction mechanisms, and synthesis methods. Finally, the challenges and prospects of the future development of high-efficiency and low-precious metal OER electrocatalysts are presented.

Development of interatomic potential suitable for molecular dynamics simulation of Ni oxidation and Ni-NiO interface.

Large-scale molecular dynamics (MD) simulations enabled by computationally efficient semiempirical potentials are an invaluable tool for materials modeling. In the case of metallic alloys, embedded atom method (EAM) and Finnis-Sinclair (FS) potentials are a reasonable choice based on their good balance of quality and computational cost. However, these semiempirical potentials are not suitable for simulating ionic systems, which prevents their use in studying many technologically relevant metal-oxide systems. The charge transfer ionic potential (CTIP), which can utilize EAM/FS potentials available in the literature together with a variable charge representation of electrostatic interactions, should be a reasonable choice for performing reliable and computationally efficient MD simulations of such systems. However, only a few such potentials are available in the literature, and their computational cost is much higher compared to EAM/FS potentials. In the present work, we have attempted to remedy these deficiencies by combining several modifications to the CTIP model proposed in the literature and efficiently implementing them into the widely used Large-scale Atomic/Molecular Massively Parallel Simulator MD code. Using these modifications, we have developed a new Ni-O CTIP parameterization, which has been tested in several different scenarios of interest. First, the early stages of Ni surface oxidation were simulated, demonstrating the nucleation and growth of a crystalline NiO film across the surface. Second, solidification and vitrification in the Ni-O system were investigated, demonstrating that the new CTIP parameterization provides reasonable agreement with the experimentally determined equilibrium phase diagram. Finally, we studied the interaction of dislocations in a Ni matrix with a NiO inclusion using a simulation cell with an unprecedented number of atoms for a variable charge MD simulation. Thus, the approach utilized in the present study is an efficient method to simulate large scale atomic mechanisms in metal-oxide systems.

Phase Field Simulation and Experimental Study of Carbide Precipitation Process in Submerged Arc Welding on Descaling Roll

The mechanical properties of surfacing layers are significantly affected by the precipitation and evolution of carbides in nickel-based alloys. At present, the study of carbide precipitation in a Ni-Cr-B-Si surfacing layer is described by using the phase field method. In this paper, the true Gibbs free energy of the M23C6 carbide phase in Ni-Cr-C ternary alloy was established by the CALPHAD method and thermodynamic database. The growth and coarsening process of M23C6 carbide was simulated based on phase field method. The microstructure of M23C6 carbide of Ni-Cr-C alloy at 1373 °C isothermal aging time was observed by scanning electron microscope (SEM). The results show that the growth and coarsening of the precipitated M23C6 carbide phase are undergone through multiple processes during isothermal aging. First, a single precipitate core is formed, and then the single precipitate continues to coarsen and grow, forming a lamellar structure. Two precipitates contact to form a single rod-like structure, and multiple precipitates form slender rod-like structures. Finally, the contacting elongated rod-like structures grow, forming a typical layered eutectic carbide. The precipitation behavior, growth, and coarsening process of M23C6-type carbides in Ni-Cr-B-Si series alloys are explored through phase field simulation and experimental research in this paper. A theoretical basis is provided for the rational control and distribution of carbides in surfacing layers. A reference is also offered for optimizing the nickel-based superalloy materials used for surfacing the surface of descaling rolls.

Liquid metal ion source based on magnetic suspensions for field emission electric propulsion (FEEP)

This work presents a process for the creation of emitter structures for liquid metal ion sources based on suspensions of iron and nickel in gallium-based room temperature liquid metal alloys. The process does not require needle etching or vacuum wetting of the emitter. Tip radii of less than 3 μm have been achieved. In addition, first measurements and observations from single emitter emission experiments are presented, including current-voltage characteristics, vacuum stability, degradation mechanisms and first thruster characteristics for the use in field emission electric propulsion. The impedance of the magnetic liquid metal emitters was found to correlate with the mass fraction of particles suspended in the liquid metal. Total impedances up to 30 MΩ have been achieved, indicating the feasibility of emitter clustering. Thrust measurements were performed with a commercial of the shelf load cell and verified in a dedicated setup for field emission electric propulsion testing, featuring a sub micro newton counterbalanced double pendulum thrust balance.

New insights on the effects of chemistry and temperature on α’ precipitation during aging of FeCrAl alloys

New insights on the effects of chemistry and temperature on α’ precipitation during aging of FeCrAl alloys

A dual-drive design strategy integrating knowledge and data for ternary precipitate-strengthened copper alloys

A dual-drive design strategy integrating knowledge and data for ternary precipitate-strengthened copper alloys

Exceptional High-Temperature Strength of a Mo-11%Hf binary alloy

The Mo-rich side of the Mo-Hf binary system exhibits a wide solubility range, up to ∼12 at% Hf at 25°C and increasing to 28% at 2165°C, in spite of the large difference in atomic sizes and elastic moduli of these elements. As a result, strong solid solution strengthening is expected and of interest for high temperature structural applications. In this work, microstructure and mechanical properties of a binary solid solution alloy Mo-11%Hf are reported after annealing at 1400°C for 5-50 hours followed by either slow cooling (SC) or water quenching (WQ). In all annealing conditions, the alloy had remnants of a dendritic structure that formed during solidification, with dendrite cores depleted in Hf and inter-dendritic continuous channels enriched with Hf. Both dendrite cores and Hf-rich channels had BCC crystal structures with similar lattice parameters and the same crystal orientation within each grain. In SC condition, Mo-11%Hf had a yield stress of 920 MPa at 25°C, which decreased to 550 MPa at 600°C, remained nearly constant up to 1200°C and then decreased to 420 MPa at 1400°C. The WQ condition was slightly stronger at 25 - 1000°C, but it was similar to SC condition at higher temperatures. The alloy showed noticeable strain hardening at all studied temperatures. Transmission electron microscopy observations showed that the deformation microstructure consisted predominantly of long bowed edge dislocations. The temperature dependence of the yield stress of the Mo-11%Hf was satisfactorily described by the Maresca-Curtin edge dislocation strengthening model.

Solidification of a quaternary X5CrNi18-10 alloy during laser beam welding using CALPHAD data in a phase-field approach

Solidification of a quaternary X5CrNi18-10 alloy during laser beam welding using CALPHAD data in a phase-field approach

Chemical short-range order and its influence on selected properties of non-dilute random alloys

In recent years, non-dilute random alloys (NDRAs) have been gaining interest as promising materials for high-temperature structural applications due to their unique ability to form solid solution phases that portray exceptional mechanical properties and resilience under extreme conditions. This study deals with the effects of chemical short-range order (CSRO) on selected material properties including lattice parameters, lattice distortion (LD), unstable stacking fault energy (USFE), and melting points (MPs). The main body of this study is on 21 ternary alloys, where the interatomic interactions are described by an embedded-atom method potential. Our results demonstrate that random structures generally exhibit larger lattice parameters and greater LD compared to CSRO structures, while CSRO structures possess higher USFEs and MPs. Furthermore, there is no discernible pattern in the segregation of the same and different atom pairs in the NDRAs, as revealed by the notably varying local ordering or segregation for most of them. Last, the effects of interatomic potential and the number of constituent elements are studied using other interatomic potentials and/or non-ternary systems, suggesting that our finding is consistent across different potentials/alloys.

Accelerating phase-field simulation of multi-component alloy solidification by shallow artificial neural network

Low computing efficiency is a significant barrier in the phase-field modeling of multi-component alloys coupled with the CALPHAD (CALculation of PHAse Diagram) method. The fundamental issue is that the quasi-equilibrium thermodynamic data (QETD) required for calculating the chemical driving force must be acquired by repeatedly solving a large number of nonlinear equations. In this work, a novel method is developed to predict the QETD by a shallow neural network in a straightforward manner, so circumventing the repetitive numerical calculation of nonlinear quasi-equilibrium thermodynamic conditions. The numerical evaluation of a Ni-Cr-Al ternary alloy demonstrates that the proposed scheme can decrease the computing consuming to about 1/80 of that required by the conventional phase-field method when the computational domain size reaches the millimeter scale, while accurately reproducing the equiaxed dendritic growth and solute segregation kinetics during polycrystalline solidification. The method presented in this work will provide an effective tool for modeling the microstructure evolution of complex materials involved in practical engineering applications.

Machine-learning-assisted catalytic performance predictions of binary alloy catalysts for glucose hydrogenation

Machine-learning-assisted catalytic performance predictions of binary alloy catalysts for glucose hydrogenation

Analytical and numerical investigation of successive metallic alloy droplets impacting onto a surface: Regime maps and scaling laws based on energy analysis

Analytical and numerical investigation of successive metallic alloy droplets impacting onto a surface: Regime maps and scaling laws based on energy analysis

A method to evaluate the processability of metallic alloys by laser-based powder bed fusion

A method to evaluate the processability of metallic alloys by laser-based powder bed fusion

Fabrication of metal alloy structures with overhang features in laser-based powder bed fusion: A critical review of challenges and latest developments

Fabrication of metal alloy structures with overhang features in laser-based powder bed fusion: A critical review of challenges and latest developments

Investigation of the Effect of Alloying Elements on the Density of Titanium-Based Biomedical Materials Using Explainable Artificial Intelligence

Titanium alloys are widely preferred in the healthcare sector as biocompatible materials due to their superior properties such as low density and exceptional mechanical strength. Their low density provides lightweight solutions, and their density is closer to that of human bone compared to other metallic alloys with similar strength. This similarity facilitates a balanced load distribution between the bone and the implant, enhancing biomechanical compatibility. This study investigates the effects of alloying elements on the density of titanium-based biomedical materials using a computational materials science approach. A total of 72 different compositions of Ti-Al-V alloys were modeled using JMatPro software, and their densities were simulated at room temperature (25°C). The simulation produced a comprehensive dataset, which was utilized to train an explainable artificial intelligence (XAI) model. Advanced interpretability techniques, including SHAP (SHapley Additive exPlanations), LIME (Local Interpretable Model-agnostic Explanations), and Partial Dependence Plots (PDP), were employed to elucidate the influence of each alloying element on the density. The dataset was analyzed using an XAI-based regression model implemented with the Artificial Neural Network (ANN) algorithm. The interpretability graphs provided insights into the individual contributions of the alloying elements, revealing their positive or negative effects on the density. The findings offer a deeper understanding of the role of alloying elements in optimizing the performance of titanium-based biomedical materials, particularly in achieving lightweight designs. This study highlights the potential of integrating computational material modeling with explainable AI to advance the design and development of high-performance lightweight materials for biomedical applications.

Ab-initio study of anomalous Hall and Nernst effects in equiatomic quaternary Heusler alloy CoFeVGe

Ab-initio study of anomalous Hall and Nernst effects in equiatomic quaternary Heusler alloy CoFeVGe

Tuning resistive switching behavior and conduction mechanism in Se80Te20 alloy with Fe, Co, Ni, and Cu additives

Abstract The present investigations comprehensively analyze the current-voltage characteristics and conduction mechanism in Se80Te20 (ST) and Se78Te20TM2 (STTM; where TM denotes transition metals Cu. Fe, Co, and Ni) glasses. This study focuses on a multi-component system and investigates the voltage-current characteristics of nearly identical disc-shaped specimens at various temperatures below their glass transition points. By analyzing the experimental data, we discovered resistive switching phenomena in the parent glass and its ternary variants containing transition metals Fe, Co, Ni, and Cu. Remarkably, the resistive switching behavior of these samples has been observed to be related to the Meyer-Neldel rule. Additionally, our findings reveal space charge-limited conduction in binary and ternary alloys. We identified linear relationships between ln I and V1/2 across both low and high voltage ranges, which we explained using the Poole-Frenkel mechanism. While the I-V characteristics showed ohmic behavior at lower voltages, a transition to non-ohmic behavior at higher voltages was attributed to voltage-induced temperature effects.

Contour parameters, melt pool behavior, and surface roughness relationships across laser powder bed fusion platforms and metallic alloys

Contour parameters, melt pool behavior, and surface roughness relationships across laser powder bed fusion platforms and metallic alloys

Antimicrobial and Antibiofilm Activities of Urinary Catheter Incorporated with ZnO-Carbon Nanotube.

Urinary tract infections are among the most common nosocomial infections, with the majority being catheter-associated urinary tract infections (CAUTIs). This study demonstrated that an antimicrobial and antibiofilm urinary catheter containing zinc oxide-carbon nanotubes (ZnO-CNT) can inhibit CAUTIs in patients. ZnO-CNT polymers were synthesized by mixing ZnO and CNT using a high-shear mixer, and the synthesized ZnO-CNT polymers were incorporated into a silicone matrix to produce a ZnO-CNT urinary catheter. Scanning electron microscopy was used to evaluate the morphology and atomic composition of the polymer and urinary catheter, which contained 1.23% Zn element. Dynamic light scattering analysis showed an average particle size of 253.4 nm with a zeta potential of +21.4 mV. To assess antimicrobial activity, the ZnO-CNT polymer and urinary catheter were tested using minimum inhibitory concentration (MIC) and antibiofilm assays. The ZnO-CNT polymers exhibited MIC values of 0.0078, 1, 0.00625, and 0.0039% against E. coli, P. aeruginosa, E. faecalis, and S. aureus, respectively. Antibiofilm assays conducted at concentrations ranging from 1/4 to 2 × MIC demonstrated effective inhibition of biofilm formation at 1 × MIC or lower concentrations in E. coli and P. aeruginosa. The ZnO-CNT urinary catheter inhibited biofilm formation by 53.42 and 56.44% after 120 h of incubation compared to the silicone urinary catheter against E. coli and P. aeruginosa, respectively. These findings suggest that the ZnO-CNT urinary catheter could not only replace commonly used silicone catheters to reduce patient discomfort but also serve as a viable alternative to antimicrobial urinary catheters coated with metal alloys such as silver, gold, or palladium.

A Review of Friction Stir Welding of Industrial Alloys: Tool Design and Process Parameters

Friction stir welding (FSW) is a pivotal technology with ongoing relevance across industries. Renowned for its ability to join materials with dissimilar melting points while mitigating thermal distortions, FSW offers relevant advantages over traditional fusion welding. However, the adoption of FSW for high-strength alloys poses notable challenges, including: (i) accelerated tool wear, (ii) the need for special tool features tailored to these alloys, and (iii) a narrow process window. This review provides a comprehensive overview of FSW as an advanced technique for joining metal alloys for several industrial fields. Emphasis is on materials such as Mg-, Cu-, Ti-, and Ni-based alloys, automotive steels, stainless steels, and maraging steels. The research highlights the critical influence of tool design—main dimensions, features, and materials—and process parameters—rotational and welding speeds, tilt angle, and plunge depth or vertical load—also considering their influences on defect formation. Detailed insights are provided into material flow and the formation of the different weld regions, including SZ, TMAZ, and HAZ.