Critical Assessment 9: Wrought magnesium alloys

This assessment is focussed on wrought magnesium alloys for lightweight applications, particularly in the transport sector. The challenges to their wider use are summarised, including poor low temperature formability, corrosion issues, dissimilar metal joining, and limited precipitation strengthening. The fundamental origins of these challenges, and current research to address them, are highlighted. Key developments such as the use of dilute rare earth additions to manipulate texture for improved formability are discussed. Opportunities to exploit the unique properties of wrought magnesium alloys where further research is required are identified.     

Microstructure and magnetostrictive performance of NbC-doped<100>oriented Fe-Ga alloys

The<100>oriented Fe83Ga17 alloy rods with various NbC contents less than 1at%were prepared by the directional solidification method at a growth rate of 720 mm?h?1. Low NbC-content was found to affect t...     

Ultrastrong Medium‐Entropy Single‐Phase Alloys Designed via Severe Lattice Distortion

Severe lattice distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium‐ and high‐entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here it is shown that a simple VCoNi equiatomic medium‐entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid‐solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe lattice distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation‐mediated plasticity effectively enhances the strength–ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe lattice distortion is a key property for identifying extra‐strong materials for structural engineering applications.     

Comparative study on the viscosity modeling of the Ag–Au–Cu liquid alloys

With the new CALPHAD-type model proposed in our previous work, the viscosity of the Ag–Au–Cu system was re-optimized. Comparisons were made in the calculated viscosities of the Ag–Au and Ag–Cu liquid alloys at 1373 K among different models. It was found that the CALPHAD-type models perform better than the empirical models. The calculated viscosities of the Ag–Au–Cu liquid alloys with and without ternary interaction parameters were both compared with the calculation results of the previous CALPHAD-type model. Considering ternary interaction, the best fitness with the experimental data could be obtained by our model. The good performance in reproducing the measured viscosities of binary and ternary systems evidences the validity of the new model.     

Advances in multimetallic alloy-based anodes for alkali-ion and alkali-metal batteries

In order to meet the growing demand of portable electronic devices and electric vehicles, enhancements in battery performance metrics are required to provide higher energy/power densities and longer cycle lives, especially for anode materials. Alloying anodes, such as Group IVA elements-based materials, are attracting increasing interest as anodes for next-generation high-performance alkali-metal-ion batteries (AMIBs) owing to their extremely high specific capacities, low working voltages, and natural abundance. Nevertheless, alloying-type anodes usually display unsatisfactory cycle life due to their intrinsic violent volumetric and structural changes during the charge–discharge process, causing mechanical fracture and exacerbating side reactions. In order to overcome these challenges, efforts have been made in recent years to manufacture multimetallic anodes that can accommodate the induced strain, thus showing high Coulomb efficiency and long cycle life. Meanwhile, much work has been conducted to understand the details of structural changes and reaction mechanisms taking place by in-situ characterization methodologies. In this paper, we review the various recent developments in multimetallic anode materials for AMIBs and shed light on optimizing the anode materials. Finally, the perspectives and future challenges in achieving the practical applications of multimetallic alloy anodes in high-energy AMIB systems are proposed.     

High-entropy alloys fabricated via powder metallurgy. A critical review

High-entropy alloys (HEAs) have attracted a great deal of interest over the last 14 years. One reason for this level of interest is related to these alloys breaking the alloying principles that have been applied for many centuries. Thus, HEAs usually possess a single phase (contrary to expectations according to the composition of the alloy) and exhibit a high level of performance in different properties related to many developing areas in industry. Despite this significant interest, most HEAs have been developed via ingot metallurgy. More recently, powder metallurgy (PM) has appeared as an interesting alternative for further developing this family of alloys to possibly widen the field of nanostructures in HEAs and improve some capabilities of these alloys. In this paper, PM methods applied to HEAs are reviewed, and some possible ways to develop the use of powders as raw materials are introduced.     

Effects of Ni Content and Ball Milling Time on the Hydrogen Storage Thermodynamics and Kinetics Performances of La–Mg–Ni Ternary Alloys

The effects of Ni content and ball milling time on the hydrogen storage thermodynamics and kinetics performances of asmilled La_5Mg_(95-x)Ni_x(x = 5, 10, 15) ternary alloys have been investigated.The evolution of microstructure and phase of experimental alloys in the absorption/desorption process has been characterized by XRD, SEM and HRTEM.The hydrogen storage kinetics and thermodynamics performances and PCI curves have been tested using the Sievert apparatus.It is found that the rising of Ni content remarkably improves the hydrogen storage kinetic performance, but reduces hydrogen storage capacity.And with the increase in milling time, hydrogen desorption activation( E_a) value decreases firstly and then increases; the minimum value is 47.6 kJ/mol, and the corresponding milling time is 10 h for La_5Mg_(85)Ni_(10) alloy.As for the thermodynamics properties, the hydrogenation enthalpy(Δ H) and hydrogenation entropy(Δ S) both decrease firstly and then increase with the rising of Ni content and milling time.The composite La_5Mg_(85)Ni_(10)alloy milled for 10 h exhibits the best thermodynamics and kinetics performances, the lowest E_a of 47.6 kJ/mol, absorption of 5.4 wt.% within 5 min and desorption of 5.2 wt.% within 3 min at 360 ℃ and the lowest Δ H and Δ S of 72.1 kJ/mol and 123.2 J/mol/K.     

Novel Bi-Doped Amorphous SnOx Nanoshells for Efficient Electrochemical CO2 Reduction into Formate at Low Overpotentials

Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO₂ reduction. Herein, the first synthesis of homogeneous Sn_1−xBi_x alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnO_x shells for efficient CO₂ reduction is reported. The Bi-SnO_x nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnO_x nanoshells derived from Sn_0.80Bi_0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm⁻² and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H₂ and CO.