Alloy Research Articles

Laser induced breakdown spectroscopy for composition monitoring of graded Al[sbnd]Cu alloy surface

Laser-induced breakdown spectroscopy (LIBS) is a powerful method for non-invasive elemental composition monitoring which can be applied for processing graded metal alloys, provided that challenges with reliable and rapid spectral data processing are overcome to enable composition analysis in real-time. In this study, we describe an integrated experimental-computational methodology for analyzing LIBS spectra data obtained from graded composition metal alloy surfaces with a mean rate of composition analysis up to 15.7 Hz. The accuracy and speed of this method was assessed via analysis of a graded AlCu film prepared by magnetron sputtering representing a gradient alloy processed by additive manufacturing. Using a pulsed femtosecond laser and gated sCMOS detector, a series of LIBS measurements were taken across the composition gradient of an AlCu sputtered alloy. Energy Dispersive Spectroscopy (EDS) was used both to calibrate composition measurements and quantify the error of the LIBS-based rapid analysis method demonstrated in this paper, which yielded a mean percent error relative to the EDS data in the composition measurement along the gradient as low as 1.4 % when optimized for the cumulative number of probe laser pulses on a single measurement spot. The femtosecond probe pulse method described in this paper allows for the alloy composition to be accurately measured in hundredths of a second, potentially allowing for real-time composition monitoring in gradient alloy processing, including thin film sputtering, additive manufacturing, and other rapid processing technologies for graded metal alloys.

Advancing the hydrogen tolerance of ultrastrong aluminum alloys via nanoprecipitate modification

Ultrastrong metallic alloys, possessing unparalleled load-bearing abilities, are coveted in many sectors, thus attracting growing research efforts. However, these alloys encounter persistent usability challenges posed by hydrogen embrittlement, which causes unpredictable fracture through crack initiation. Due to complex hydrogen-microstructure interactions and their exacerbation under high stress, advances in hydrogen resistance in ultrastrong materials are sparse throughout their long history. Herein, we report a quantum-mechanics-informed strategy for hydrogen tolerance enhancement in ultrafine-grain-hardened Al-Zn-Mg-Cu alloys, approaching their current strength limit of approximately 1 GPa. This method involves the incorporation of hydrogen-absorbing T-phase precipitates into nanograins, to substantially reduce hydrogen coverage at potential crack initiation sites. We demonstrate, via synchrotron radiation X-ray micro-/nano-tomography, scanning transmission electron microscopy and atom probe tomography, that nanoprecipitates successfully withstand shear strains exceeding 1000 and are exploitable essentials for ultra strength-hydrogen synergy, contrasting their often-assumed secondary roles in nanocrystalline alloys due to possible strain-induced dissolution, which has intuitively excluded exploring them as central elements. Our approach potentially inspires new hydrogen-resisting alloys across a broad strength-composition space.

Composition dependence of phase transformation and shape memory effect of Ti-Zr-Pd-Pt high temperature shape memory alloys

Ti-Zr-Pd-Pt alloys have been considered as potential candidates for high-temperature shape memory alloys (HT-SMAs). In this study, nine alloys were prepared to investigate the effect of multi-component alloying on the phase transformation and shape memory effect. The structural phase diagram of martensite in Ti–Zr–Pd–Pt quaternary alloys was firstly systematically investigated to provide insights and predictions for further research. The phase transformation is divided into three groups: typical martensitic transformation (MT) area, supercooling-controlled phase transformation area and diffusion-assisted phase transformation area. The martensite structure changes from B19 to B33 with the addition of Zr over 25 %. The contribution of Pt contents to raising the martensitic transformation temperature (MTT) became less pronounced with increasing Zr contents. As for shape recovery, over 87 % shape recovery was obtained even under 300 MPa in Ti-10Zr-Pd-Pt alloys, among which Ti-10Zr-15Pt-35Pd presents the highest recovery ratio of over 97 %.

Unsupervised machine learning and cepstral analysis with 4D-STEM for characterizing complex microstructures of metallic alloys

Four-dimensional scanning transmission electron microscopy, coupled with a wide array of data analytics, has unveiled new insights into complex materials. Here, we introduce a straightforward unsupervised machine learning approach that entails dimensionality reduction and clustering with minimal hyperparameter tuning to semi-automatically identify unique coexisting structures in metallic alloys. Applying cepstral transformation to the original diffraction dataset improves this process by effectively isolating phase information from potential signal ambiguity caused by sample tilt and thickness variations, commonly observed in electron diffraction patterns. In a case study of a NiTiHfAl shape memory alloy, conventional scanning transmission electron microscopy imaging struggles to accurately identify a low-contrast precipitate at lower magnifications, posing challenges for microscale analyses. We find that our method efficiently separates multiple coherent structures while using objective means of determining hyperparameters. Furthermore, we demonstrate how the clustering result facilitates more robust strain mapping to provide immediate and quantitative structural insights.

Sub-2 nm Ternary Metallic Alloy Encapsulated within Montmorillonite Interlayers for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis

Sub-2 nm Ternary Metallic Alloy Encapsulated within Montmorillonite Interlayers for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis

Revealing extraordinary plasticity in single crystal Fe-15Mn-10Cr-8Ni-4Si alloy

An extraordinary elongation of over 156 % was achieved in single crystal Fe-15Mn-10Cr-8Ni-4Si alloy, which shows γ → ε → α’ transformation. Tensile tests were conducted along the 〈414〉, 〈111〉, and 〈100〉 directions, and the deformed microstructure was characterized with electron-backscattering diffraction (EBSD). Elongation in 〈414〉 orientation (156 %) was highest as ever recorded in metallic alloy—approximately twice that of conventional TWIP steels. Mechanical behavior in 〈414〉 is characterized with slow work hardening, with upward curvature in the stress–strain curve. EBSD analysis revealed 45 % of ε-martensite and significant γ-twin microstructure components in 〈414〉. In initial stage, deformation was marked by planar slip and a sluggish γ → ε transformation, activating a single ε-martensite variant with a Schmid factor of 0.5. Later stages witnessed crystal rotation towards 〈112〉, generating multiple shear bands and distinct ε variants. Fractures predominantly occurred along the 〈011〉 direction, with the fracture surface exhibiting a ductile nature.

Multiphysics computational modelling and experimental analysis of friction stir welding of aluminium alloy metal matrix composites (AAMMCs)

Friction stir welding is a modern method for fabricating aluminium alloy metal matrix composites (AAMMCs) that significantly enhance the properties of the parent materials. In this study, Al2O3 particles were incorporated into a 6061-T6 aluminium matrix. Experimental and numerical modeling provided in-situ observations of particle-aluminium matrix mixing in the weld stir zone (SZ). Two different pin profiles, threaded and square, were used to fabricate the AAMMC joints. The threaded pin profile resulted in uniform dispersion and a homogeneous distribution of Al2O3 particles within the aluminium matrix. In contrast, the square pin profile led to defects in the SZ and a non-homogeneous particle distribution. The volume fraction mixing of the AA6061-T6 matrix and Al2O3 at the workpiece/tool interface from top to bottom was analyzed using a level set technique. Experimental results showed effective mixing of Al2O3 particles in the AA6061-T6 matrix with the threaded pin profile, resulting in a defect-free joint, uniform particle distribution, and ultra-fine grain refinement, with grain sizes reduced to 4.19 µm. The main shear texture components observed in the threaded pin joints included B/B̅ and C, along with deformed and recrystallized texture components such as Copper {112} 〈111〉, Brass {110} 〈112〉, Goss {011} 〈100〉, Cube {001} 〈101〉, and P {011} 〈112〉 . Additionally, joints fabricated using threaded pin profiles exhibited significantly higher tensile strength (up to 270 MPa) and microhardness (average of 120 HV0.2) compared to those with square-shaped pin profiles, which showed lower values of 240 MPa and 105 HV0.2, respectively. Thus, AAMMC joints made with threaded pins demonstrate ultra-fine grain refinement, increased high-angle grain boundaries, enhanced recrystallized texture components, and improved mechanical properties, resulting in superior overall joint performance.

Effect of Nonessential Alloying Elements and Solution pH on Corrosion Behavior of Al-Mg Alloys Fabricated by Cold Spray Deposition

This paper highlights the difference in corrosion behavior of cold spray (CS) deposited AA5083 and Al-5.0 wt% Mg alloys with an emphasis on the effect of nonessential alloying elements and solution pH. CS process is an emerging technology for repairing damaged structures via solid-state deposition. While recent works have focused on CS Al alloys, less attention has been paid to CS Al binary alloys in comparison to Al engineering alloys, which have important implications for the integrity of structural components repaired by the CS process. Herein, the microstructure of CS AA5083 and Al-5.0 wt% Mg binary alloy was analyzed using various microstructure characterization techniques. Corrosion behavior was assessed using electrochemical and immersion tests in 0.6 M NaCl (pH 8.3 and 11.5) solution. Intermetallic phases, such as Fe- and Si-containing phases, in CS AA5083 decreased corrosion resistance by increasing cathodic kinetics in a near-neutral solution. In addition, immersion tests demonstrated lower corrosion resistance in CS AA5083 than in CS Al-5.0 wt% Mg, whereas an alkaline environment showed the presence of a secondary passive layer on CS AA5083, providing higher corrosion resistance compared to CS Al-5.0 wt% Mg.

Damping capacity in cast FeMn binary alloys

There were few works on cast FeMn binary damping alloys, although many studies have been conducted on deformation-processed counterparts. The cast Fe(15–21)Mn alloys were prepared to investigate their damping capacity in this work. The optimal Mn contents for damping capacity in both the as-cast FeMn binary alloys and solution-treated ones was ∼ 19 %, 2 % higher than that in the deformation-processed counterparts. The solution treatment obviously improved the damping capacity in the as-cast Fe15Mn alloys but remarkably deteriorated the damping capacity in the as-cast FeMn alloys with the Mn content above 17 %. An inverse dependence on the amount of α′-martensite existed in both the as-cast Fe(15–19)Mn alloys and solution-treated ones, but the dependence was weak in the latter. The dual role played by the α′-martensite could explain the different effects of it on the damping capacity.

ScAlInN/GaN heterostructures grown by molecular beam epitaxy

Rare-earth (RE) elements doped III-nitride semiconductors have garnered attention for their potential in advanced high-frequency and high-power electronic applications. We report on the molecular beam epitaxy of quaternary alloy ScAlInN, which is an encouraging strategy to improve the heterointerface quality when grown at relatively low temperatures. Monocrystalline wurtzite phase and uniform domain structures are achieved in ScAlInN/GaN heterostructures, featuring atomically sharp interface. ScAlInN (the Sc content in the ScAlN fraction is 14%) films with lower In contents (less than 6%) are nearly lattice matched to GaN, exhibiting negligible in-plane strain, which are excellent barrier layer candidates for GaN high electron mobility transistors (HEMTs). Using a 15-nm-thick Sc0.13Al0.83In0.04N as a barrier layer in GaN HEMT, a two-dimensional electron gas density of 4.00 × 1013 cm−2 and a Hall mobility of 928 cm2/V s, with a corresponding sheet resistance of 169 Ω/□, have been achieved. This work underscores the potential of alloy engineering to adjust lattice parameters, bandgap, polarization, interfaces, and strain in emerging RE-III-nitrides, paving the way for their use in next-generation optoelectronic, electronic, acoustic, and ferroelectric applications.

Solidification Microstructure and Mechanical Properties of B1-type TiC in Fe–Ti–C Ternary Alloys

Solidification Microstructure and Mechanical Properties of B1-type TiC in Fe–Ti–C Ternary Alloys

Investigation of microstructural and thermal stability of Ni-Y-Zr ternary nanocrystalline alloy

This investigation focused on the thermal stability of nanocrystalline (NC) binary and ternary Ni-Y-Zr alloys synthesized through ball-milling. The microstructural changes following annealing, conducted up to 1200 °C, were studied using various techniques, including X-ray-line-broadening, micro-hardness, and transmission electron microscopy. The results revealed that the rate of grain growth observed in the Ni-Y-Zr ternary alloy at 600 °C resembled that in pure NC-Ni at 100 °C. Moreover, the Ni-1.4Y-1.1Zr ternary system exhibited a maximum hardness of 753 HV (average) at 600 °C, which was approximately 60 HV higher than the Ni-1.2Y/1.9Y and Ni-1.5Zr/2.7Zr binary alloys and more than double that of pure NC-Ni for similar grain sizes. These characteristics were linked to the formation of nano-sized oxides and nitrides of Y and Zr within the microstructure. In summary, this study emphasizes the notable high-temperature microstructure stability of Ni-based ternary alloys, attributed to the additive effects of Y and Zr. Due to this extended stability, this ternary system could find potential applications at elevated temperatures in areas such as jet engine turbine blades and power plants.

A novel design of energy absorption branch for HVDC circuit breakers

Metal oxide varistors (MOV) used for energy absorption branch in DC circuit breakers are complex enough to meet the requirements for small volume, light weight, and reliability in future high-voltage direct current (HVDC) grids. Therefore, a new energy absorption branch circuit that combines MOV and a liquid metal alloy energy absorber (LMEA) is proposed. Based on the constructed equivalent mathematical model of LMEA, the working principle and energy absorption process of MOV and LMEA in DC breaking process are analysed in PSCAD/EMTDC simulation software. Results demonstrate that LMEA, in contrast to MOV alone, absorbs 2.12 MJ of energy, constituting 35.6% of the total energy. Moreover, LMEA enhances energy dissipation density while reducing volume. Experimental analysis reveals MOV’s energy absorption mechanism via achieving residual voltage with ZnO varistor’s non-linear properties, swiftly transitioning from high to low resistance states to absorb energy. Conversely, LMEA relies on pulse current amplitude to initiate internal arcing, sharply increasing internal resistance for effective energy absorption. Experimental findings validate LMEA’s contribution of one-third of total energy absorption when pulse current amplitude reaches critical arcing threshold, consistent with simulation results. The results provide theoretical support for the engineering application of the new liquid metal alloy energy absorption in DC circuit breakers.

Study on the complications after implantation of different types of metal stents in rabbit trachea

ObjectiveTo observe the complications and inflammatory responses caused by the different types of metal stents in the trachea of rabbits. Method79 rabbits were randomly divided into 4 groups and were implanted with the customized nickel-titanium alloy metal stents(fully covered metal stent: group A, bare metal stent: group B, segmented covered metal stent: group C and control group: group D). The complications (tracheal deformation, granulation tissue hyperplasia, scar hyperplasia and secretion retention) of different types of metal stents were compared by observing the anatomical and pathological specimens of dead rabbits; And the expression of inflammatory factors of different types of metal stents were compared by detecting the tissue of tracheas of dead rabbits. Results(1)There were significant differences in the above four complications among groups A, B and C(p < 0.01). The incidences of tracheal deformation, scar hyperplasia and secretion retention in group A were significantly higher than that in group B(p < 0.0167), however, the incidence of granulation tissue hyperplasia in group A was significantly lower than that in group B(p < 0.0167). The incidence of scar hyperplasia in group A was significantly lower than that in group C(p < 0.0167) and there were no significant differences in other complications between these two groups(p > 0.0167). The incidences of tracheal deformation, scar hyperplasia and secretion retention in group B were significantly lower than that in group C(p < 0.0167), however, the incidence of granulation tissue hyperplasia in group B was significantly higher than that in group C(p < 0.0167). (2)The concentration of IL-1β in group A was higher than that in group B (p < 0.05 and foldchange>1.2). Conclusion(1)There are significant differences in complications between the fully covered metal stent, bare metal stent and segmented covered metal stent; the incidences of complications between the segmented covered metal stent and fully covered metal stent are similar. (2)Changes in different inflammatory factors can be observed between the fully covered and bare metal stent.

Excellent magnetocaloric effect near the hydrogen liquefaction temperature of a binary Er67.5Co32.5 metallic glass

We reported the excellent magnetocaloric effect of a binary Er67.5Co32.5 metallic glass (MG) near the hydrogen liquefaction temperature. The binary MG ribbon was fabricated by a melt-spinning method. The Er67.5Co32.5 alloy exhibits a better glass formability than most of other rare earth (RE)-Co binary alloys. The maximum magnetic entropy change (−ΔSmpeak) and refrigeration capacity (RC) of the Er67.5Co32.5 amorphous ribbon under 0–5 T reach to 17.47 J/(kg × K) near its Curie temperature (Tc, ∼ 11 K) and 472 J/kg, both of which are rather high among the RE-based MGs with a Tc around 10 K and imply the potential application perspective as magnetic refrigerants for hydrogen liquefaction. The magnetization as well as magnetocaloric behaviors of the binary MG were observed, and the mechanism involved was investigated.

Fe-Ni binder modified NbC cermets: A cost-effective solution with superior mechanical properties

NbC-Ni cermets have emerged as promising alternatives to the conventional WC-Co due to their superior hot hardness and fracture toughness. However, the recent increase in Ni and Co prices necessitates substituting these binders with economical alternatives for cermet formulations. The Fe-Ni binary alloy shows promise as a binder due to its superior mechanical properties, low cost, and reduced toxicity compared to Co and Ni. This study demonstrated the potential of Fe-Ni as a promising binder material for NbC cermets, offering a balance between cost-effectiveness and properties suitable for various high-performance applications. The NbC-Fe-Ni cermets were fabricated via vacuum Liquid Phase Sintering (LPS) at 1440 °C for 1h and compared to NbC-Ni cermets. Microstructural analysis (SEM + EDX) revealed a continuous decrease in D90 values up to NbC-35Ni-65Fe (65 wt% Fe), indicating that Fe-Ni effectively suppressed grain growth; additionally, it increased the contiguity of NbC grains. Vickers hardness tests revealed that the hardness of the cermets increased with higher Fe content in the binder, reaching a peak value of 1487 ± 15 HV30 for NbC-35Ni-65Fe, marking a remarkable 34 % improvement over NbC-Ni. However, fracture toughness decreased marginally due to the increased contiguity of NbC grains, which reduced crack inhibition. Nanoindentation hardness tests of the binder phase revealed that partial substitution of Ni with Fe enhanced binder hardness, contributing to the overall improvement in NbC-Fe-Ni cermets' hardness values. A 3-point bend test demonstrated a maximum strength of 649 ± 16 MPa for NbC-35Ni-65Fe cermet, indicating a 19 % improvement over NbC-Ni cermet. These findings highlight Fe-Ni's potential as a cost-effective binder for NbC cermets, suitable for high-performance applications.

Microstructure and improved hydrogen generation performance via hydrolysis of Mg–Ca alloys with TiC and Ni addition

Mg-xCa (x = 3, 7, 11, 14, wt.%) binary hypoeutectic alloys are successfully synthesized via solidification in the present work. The microstructure, phase compositions and hydrogen generation characteristics of as-cast Mg–Ca alloys and ball milled Mg–Ca composites with TiC and Ni addition have been investigated in this work for a new hydrogen supply source application. A lamellar structure with alternately distributed Mg and Mg2Ca is formed in the eutectic regions of as-cast Mg–Ca binary alloys. It is found that as-cast Mg–Ca binary alloys show extremely sluggish hydrolysis kinetics and low hydrogen yield in both tap water and simulated seawater. Mg2Ca phase preferentially reacts with water during hydrolysis process in simulated seawater. Many cracks arise with hydrolysis reaction, meanwhile, the cracks further assist in the hydrolysis of the internal matrix via assisting water solution transfer. After ball milling with TiC and Ni of Mg–Ca binary alloys, the hydrolysis performance is substantially modified. Mg–14Ca-3wt.%TiC-5wt.%Ni composite generates 836.6 mL g−1 of hydrogen within initial 95 min. The conversion rate of Mg–14Ca-3wt.%TiC-5wt.%Ni composite in simulated seawater is as high as 99.4%, indicating a thorough hydrolysis of Mg and Mg2Ca phases with the catalysis of TiC and Ni. This work shows that microstructure refinement, catalysis, Mg(OH)2 exfoliation and water solution transfer account for the complete hydrolysis.

Investigating the orientation dependence of local fields around spherical defects using crystal plasticity simulations

The presence of a void or secondary particle plays a crucial role in both the mechanical response and damage evolution of metals. This work presents local stress and strain field predictions in a single crystalline matrix that contains a spherical void or hard particle using crystal plasticity finite element method (CP-FEM) simulations. Simulations demonstrate highly heterogeneous orientation dependent local fields near defects. In particular, we show that matrix decohesion around hard particles will occur first before void growth in pre-existing voids under strain-controlled uniaxial tension and isochoric loading. Furthermore, CP-FEM simulations predict that the [1̄11]-oriented grain is most susceptible for failure, while grains oriented toward the [001] orientation are more resistant to failure. This work provides insights into how grain-scale microstructure with volumetric defects influence the local damage and failure behavior in metal alloys.

Facile synthesis of MOF-derived carbon-supported LaZn@C nanocomposite as an efficient electrode material for supercapacitor

MOF-derived transition metal alloys have attracted researcher's interest in energy storage devices due to their vast surface area, high porosity, adjustable pore sizes, ease of modification, abundant active sites, and 3D tunable structure. Metal alloys covered with carbon can stabilize conductivity and ease charge accumulation, and they are suitable candidates for electrode materials for supercapacitor application. In this research article, core-shell LaZn@C nanocomposites were fabricated at different pyrolysis times via a hydrothermal approach. The materials that pyrolysis for two hours have a remarkable specific capacitance of 1024 F g−1 at 1 A g−1 and an impressive energy density of 36.9 Whkg−1. In addition, it has lower Rp∼0.8 Ω and Rs∼0.2 Ω resistance due to the large surface area's high carbon content with cylindrical particles. Moreover, it shows an outstanding retention rate of (94.5 % over 4500 cycles at 1 A g−1). Finally, this research showed the novelty of advanced MOF-derived materials that suggest an efficient electrode material for the electrochemical performance of energy storage devices and supercapacitor applications.

Use of third generation data for the pure elements to model the thermodynamics of binary alloy systems: Part 3 – The theoretical prediction of the Al–Si–Zn system

In a previous paper a method was developed to define Einstein temperatures for metastable phases of the elements and their relation to the so-called lattice stabilities used in the past, and also the variation of the Einstein temperature with composition to account for the composition dependence of the excess entropy. This approach was demonstrated successfully for the Al–Zn system. In this paper this approach is extended to cover the Al–Si and Si–Zn binary systems. The phase diagram for the Al–Si–Zn ternary system was then predicted from the thermodynamic description of the binary subsystems only without any ternary interaction parameters. Agreement with the experimental data is shown to be very good.