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The article presents the study of the magnetocaloric effect (MCE) for the rhombohedral Laves phase of Pr 2 Rh 3 Ge, which shows a magnetic order below T C = 8.5 K. We have established that the compound exhibits a continuous second-order type of transition which was demonstrated and confirmed by several different techniques, mainly by analyzing universal curves of normalized entropy change as a function of scaled temperature. The observed MCE, in our opinion, is a consequence of an indirect exchange coupling between the magnetic sublattices of the rare earth ions, which, however, does not exclude the potential contribution of sublattice-containing transition metals. In this paper, the procedure to evaluate the MCE from magnetization and specific heat data is described. As a result, important parameters such as the isothermal magnetic entropy change (Δ S M), adiabatic temperature change (Δ T a d ), relative cooling power (RCP), and the temperature averaged entropy change (TEC) were determined. The highest values of − Δ S M , Δ T a d , and RCP for a field change (Δ μ 0 H) of 5 T at T C are 5.96 J/kg K, 3.87 K, and 72.62 J/kg, respectively. These results obtained for Pr 2 Rh 3 Ge seem to be, however, low compared to the values obtained for the rhombohedral Laves phases, belonging to the group of ternary germanides RE 2 Rh 3 Ge containing heavy rare earth metals (RE = Gd, Tb, Ho, and Er). Nevertheless, we believe that the results presented in this work extend and complement the current knowledge on the magnetocaloric properties of this family of materials. [ABSTRACT FROM AUTHOR]

Tribaloy™ T800, a Co-based alloy, exhibits remarkable tribological properties by virtue of its high-volume fraction of intermetallic Laves phase making it an attractive hard-facing material. Hard-facing by laser deposition results in dilution from the substrate, and thereby, the properties of the clad are altered. This paper reports the influence of processing parameters on the dilution, microstructure, and wear behaviour of Tribaloy™ T800 on AISI 316 stainless steel. A systematic set of 20 clads was deposited by varying laser power and cladding speed, keeping powder flow and spot diameter constant. While dilution decreased at lower laser powers (800 and 1000 W) with increasing cladding speed (5–20 mm s−1), at higher laser powers (1200 and 1400 W), the opposite trend was observed. The Fe intermixing from the substrate along with the cooling rate governs the volume fraction and size of the Laves phases which controls the properties of T800 clads. The clad with the least geometric dilution (5.7%) exhibits the lowest wear rate of 0.54 × 10−5 mm3 N−1 m−1, increasing to 2.88 × 10−5 mm3 N−1 m−1 as the dilution increased to 60%. [ABSTRACT FROM AUTHOR]

Due to the recurrent starting and stopping operations of automobiles during service, their engines' hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion. [ABSTRACT FROM AUTHOR]

The wrought nickel–chromium–cobalt Nimonic 90 alloy is widely used in turbine blades, piston rings and forged tools due to their high stress-rupture strength and creep resistance up to 920∘C. The application components showed unavoidable wear behaviors at high loads due to the reduced resistance of the components. Hence, in order to increase the wear resistance of this alloy, Inconel 625 and Nimonic 90 particle depositions have been carried out on Nimonic 90 substrate through the laser-cladding techniques to study the microstructure, mechanical and tribological behaviors of alloys. The phases, microstructure and microhardness of the claddings were investigated by X-ray diffractometry (XRD), Transmission electron microscopy (TEM), Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS) and hardness test, respectively. Results showed that the mean thickness of the interfacial layer of Inconel 625 and Nimonic 90 was 18.51 ± 4 μ m and 90.68 ± 7 μ m, respectively. The microstructure of the cladding surfaces resulted in dendritic and interdendritic structures. An overall analysis found that the gamma-Ni and hard laves phases were presented in Inconel 625 and Nimonic 90 clad surfaces, respectively. Nimonic 90 clad surface had a high hardness and wear resistance compared with Inconel 625 clad surface and substrate due to the present hard laves phase. Besides, the roughness of the Nimonic 90 clad surface was lower compared with the Inconel 625 clad surface and substrate. [ABSTRACT FROM AUTHOR]

For Intermediate-Temperature SOFC, the lower operating temperature allows for a broader range of steel grades to be used as interconnects. This work compares the oxidation performances of six Cr 2 O 3 -forming steels and one Al 2 O 3 -forming steel, under single- and dual-atmosphere conditions. Single-atmosphere exposures in combination with Cr(VI) evaporation measurements were carried out at 600 °C. Except for AISI 430 all the Cr 2 O 3 -forming steels showed protective behaviour with similar Cr(VI) evaporation values and low area specific resistance (ASR) values. Kanthal EF101 showed the lowest level of Cr(VI) vaporisation but substantially higher ASR values. Dual-atmosphere exposures were carried out at 600 °C in Ar-5%H 2 –3%H 2 O//air-3%H 2 O. All Cr 2 O 3 -forming steels suffered various degrees of breakaway corrosion. Therefore, operation under dual-atmosphere conditions is likely the life-time-limiting failure mode. • Different grades of steels are investigated under simulated IT-SOFC conditions (single and dual-atmosphere conditions). • Similar Cr(VI) evaporation levels for all Cr 2 O 3 -forming steel and very low levels for the Al 2 O 3 -forming alloy are observed. • Low ASR values for most Cr 2 O 3 -forming steels and higher ASR values for Al 2 O 3 -forming alloy are observed. • Under dual-atmosphere all Cr 2 O 3 -forming steels exhibit breakaway corrosion while the Al 2 O 3 -forming alloy stays protective. • Laves phase precipitates may increase the corrosion of FeCr alloys under dual-atmosphere conditions. [ABSTRACT FROM AUTHOR]

This study aims to investigate the impact of substrate preheating on the cracking and wear resistance of laser-clad T-800 alloy coatings on DD5 single-crystal alloy substrates. Two different conditions, namely non-preheated (22 °C) and preheated (300 °C), were employed to deposit T-800 alloy coatings on the surface of DD5 single-crystal alloy using laser cladding technology. The experimental results reveal that substrate preheating at 300 °C reduces the degree of variation in microstructure morphology within each region of the coating. This reduction effectively mitigates the internal stresses caused by the difference in solidification rates of the various parts of the coating, thereby preventing coating cracking. Additionally, the presence of Ni in the DD5 substrate enhances the dilution effect on the coating. Compared to the non-preheated condition, the preheated condition increases the Ni content in the primary Laves phase, secondary spherical Laves phase, and Co-based solid solution of the coating by 6.6%, 7.5%, and 14.8%, respectively, and the Co, Cr, Mo, and Si contents were all reduced. Consequently, this reduces the primary Laves phase and secondary spherical Laves phase precipitation and further inhibits coating cracking. The crack defects within the coating in the non-preheated condition of the substrate weakened its wear resistance. Despite a 13.6% reduction in coating microhardness attributed to preheating of the substrate, the high hardness properties of the T-800 alloy coating were preserved. Moreover, the internal hard Laves phase structure was more diffusely distributed in the softer Co-based solid solution, resulting in improved wear resistance through increased anti-adhesion ability and resistance to hard particles intrusion. Specifically, the preheated coating shows a 14.0% reduction in average coefficient of friction, a 37.9% reduction in mass loss. The wear mechanisms observed in the coatings include abrasive wear, adhesive wear, and oxidative wear. [ABSTRACT FROM AUTHOR]

This study reports on the as-cast microstructures of AlCrFeMnV, AlCrFeTiV, and AlCrMnTiV equimolar multi-principal element alloys. Thermodynamic modeling predicts that these alloys solidify as BCC solid solutions, with additional phases forming at lower temperatures. We present the measured densities, the elastic modulus values measured by nanoindentation, and the Vickers microhardness of the alloys. These properties are correlated to the underlying microstructures, as measured by x-ray diffraction, scanning electron microscopy, and atom-probe tomography. The densities of the alloys range from 5.53 to 6.42 × 10 3 kg m − 3 . The elastic modulus of AlCrFeMnV, AlCrFeTiV, and AlCrMnTiV are 211, 194, and 175 GPa, respectively, and their Vickers microhardness values are 3.9, 6.1, and 5.7 GPa, respectively. After arc-melting, AlCrFeMnV and AlCrFeTiV are BCC solid solutions while AlCrMnTiV has two phases: a BCC phase and a minor hexagonal C14 Laves phase that is enriched in V and Cr. [ABSTRACT FROM AUTHOR]

Due to the poor activation performance and kinetics of Ti50V25Cr25 alloys, the element Zr was added to improve the phase structure of the alloy and achieve a high-performance hydrogen storage alloy. The Ti50−xV25Cr25Zrx (x = 0, 5, 7, and 9) system alloys were prepared by arc melting. The alloys were analyzed using an X-ray diffractometer (XRD), scanning electron microscope (SEM), and differential scanning calorimeter (DSC). The hydrogen storage capabilities of the alloys were also obtained by the Sievert volumetric method. The results indicated that the alloy with Zr added had a combination of the C15 Laves phase and the BCC phase, whereas the Zr-free alloy had a BCC single phase. The partial replacement of Zr with Ti resulted in an increase in the lattice parameters of the main phase. The hydrogen storage kinetic performance and activation of the alloys both significantly improved with an increasing Zr concentration. The time to reach 90% of the maximum hydrogen storage capacity decreased to 2946 s, 230 s, and 120 s, respectively, with the increases in Zr concentration. The initial hydrogen absorption content of the alloys increased and then decreased after the addition of the element Zr. The second phase expanded with an increasing Zr concentration, which in turn decreased the abundance of the BCC main phase. The Ti43V25Cr25Zr7 alloy showed good cycle stability and hydrogen-desorption performance, and it could absorb 90% of the maximum hydrogen storage capacity in around 230 s. The maximum hydrogen-absorption capacity of the alloy was 2.7 wt%. The diffusion activation energy of hydrogen desorption dropped from 102.67 kJ/mol to 92.62 kJ/mol. [ABSTRACT FROM AUTHOR]

P91 steel is an important steam pipe for ultra-supercritical power plants due to its excellent creep strength, which generally has a design life of 100,000 h. Here, we found a significant aberrant decrease in the creep rupture life of a main steam pipe elbow after only 20,000 h of service. The microstructure in the aberrant piece exhibited a decomposition of martensitic lath into blocky ferrite due to recrystallization and accumulation of M23C6 as well as formation of the Laves phase along the prior austenitic grain boundaries, resulting in the decrease of hardness that no long meet ASME standard requirement. The creep testing of the P91 piece at 550–600 °C and 85–140 MPa shows that the influence of temperature on the cavity formation and cracking is greater than that of the applied stress. The rupture life is nearly two orders of magnitude shorter than the normal P91, attributing to the creep damage of the subgrain growth, M23C6 and Laves phase coarsening (aggregation approaching 3.4 μm). The residual life of the aberrant piece was evaluated to be 53,353 h based on the Larson–Miller parameter, which is much shorter than the design life, suggesting the safety operation of the elbow area should be paid more attention during the afterward service periods. P91 steel, main steam pipe elbow, aberrant microstructure, service degradation, creep life prediction [ABSTRACT FROM AUTHOR]

P92 (9Cr-1.8W–0.5Mo-NbV) martensite steel is widely used in high-temperature pipes of ultra-supercritical boilers in China. During high-temperature operation, microstructural evolution of the heat affected zone (HAZ) across welded joint leads to type IV cracking failure. In this article, microstructural evolution and type IV cracking of P92 steel welded joint in an actual 605℃ supercritical boiler were analysed. The results show the cracking appeared in the fine-grained heat affected zone (FGHAZ). Laves phase and M23C6 phase clustered around the cavity. Their precipitation and coarsening promote the nucleation and growth of cavities. The Z phase was also observed in the heated affected zone. Compared with other zones, FGHAZ has lower dislocation density and more degeneration of tempered martensite lath, the coarsening of Laves phase and M23C6 phase is more severer in FGHAZ. These factors led to the deterioration of the creep properties and type IV cracking. [ABSTRACT FROM AUTHOR]

This study investigated the first hydrogenation behavior of TiFe-based hydrogen storage alloy with the laves phase. A TiFe 0.9 Cr 0.1 alloy was prepared through vacuum arc melting, and it had a dual-phase microstructure with B2 and laves phases. The first hydrogenation kinetics was measured by applying a hydrogen pressure of 40 bar at 30 °C, where the alloy absorbed hydrogen without thermal activation. The first hydrogenation kinetics was divided into three sections to understand the first hydrogenation behavior, and each section was analyzed using a solid–gas reaction model. The model's goodness of fit was evaluated by fitting each section. In the early hydrogen absorption stage, a surface-controlled mechanism (Chemisorption model) was analyzed to be the most dominant. In the second stage, where hydrogen was quickly absorbed, an interface-controlled mechanism (CV3D model) was most suitable. In the last hydrogen absorption stage, where hydrogen absorption was saturated, a diffusion-controlled mechanism (GB3D model) was most suitable. • The TiFe 0.9 Cr 0.1 alloy had a dual-phase microstructure with B2 and laves phases. • The alloy absorbed hydrogen without any thermal activation process. • The first hydrogenation kinetics was divided into three sections for analysis. • Hydrogen absorption behavior was analyzed through the solid-gas reaction model. [ABSTRACT FROM AUTHOR]

The effects of homogenization temperature and time on microstructure and eutectic precipitates in Ce‐containing heat‐resistant stainless steel are studied. The increase in the homogenization temperature and time promotes the diffusion of alloying elements and the transition from dendrite structure to austenitic grain. Laves phase particles are fully dissolved after the homogenization of the ingots regardless of the cerium contents and homogenization temperature and time, except for the case of the homogenization at 1130 °C for 4 h. Honeycomb Laves phases gradually dissolve and become clusters of small blocky during homogenization treatment. The amount of eutectic NbC dissolved into the matrix is increased with the increase in the homogenization temperature and time. The solubility of niobium and carbon in austenite is increased with increasing the cerium content, which is beneficial to the dissolution of eutectic NbC. The distribution homogeneity of alloying elements in the austenitic matrix is increased with the increase in the cerium content. The homogenization temperature for reaching full diffusion of alloying elements into austenitic matrix is decreased with increasing the homogenization time. The decrease in the secondary dendrite arm spacing by cerium addition is favorable to the homogenization of alloying elements during homogenization treatment. [ABSTRACT FROM AUTHOR]

The development of alloys with substantial hydrogen storage capacities is a potential solution to the demand for hydrogen storage in a future hydrogen‐based energy system. The synthesis, structural‐microstructural properties, and hydrogen storage performance of a multicomponent TiZrVCrNi high‐entropy melt‐spun ribbon have been discussed in the present investigation. The x‐ray diffraction and transmission electron microscopy investigations confirm that this as‐cast and melt‐spun alloy contains only a single C14‐type hexagonal (a = b = 5.02 Å, c = 8.15 Å, α = β = 90°, γ = 120°) Laves phase. The room temperature pressure composition isotherms were studied with a pressure range of 0 to 40 atm. Continuing from our previous study in which we reported a hydrogen storage capacity of ~1.5 wt% in an as‐cast high‐entropy alloy synthesized using Arc melting, the total hydrogen storage capacity of TiZrVCrNi high‐entropy melt‐spun ribbons was found to be ~2 wt% in this work. This study makes the way forward for greater hydrogen storage in melt‐spun ribbons. The observation of only minimal losses in storage capacity, even after 10 cycles of experiments on hydrogen absorption, shows that the reversible hydrogen storage capacity has high durability. To the best of our knowledge, these demonstrations are the first to present a study on the hydrogen storage capacity (~2 wt%) of the equiatomic TiZrVCrNi melt‐spun ribbons. [ABSTRACT FROM AUTHOR]

Cylindrical Inconel 718 specimens were fabricated via a blown-powder, laser-directed energy deposition (DED-L) additive manufacturing (AM) process equipped with a dual thermal monitoring system to learn key process–structure relationships. Thermographic inspection of the heat affected zone (HAZ) and melt pool was performed with different layer-to-layer time intervals of ~0 s, 5 s, and 10 s, using an infrared camera and dual-wavelength pyrometer, respectively. Maximum melt pool temperatures were found to increase with layer number within a substrate affected zone (SAZ), and then asymptotically decrease. As the layer-to-layer time interval increased the HAZ temperature responses became more repetitive, indicating a desirable approach for achieving a more homogeneous microstructure along the height of a part. Microstructural variations in grain size and the coexistence of specific precipitate phases and Laves phases persisted among the investigated samples despite the employed standard heat treatment. This indicates that the effectiveness of any post DED-L heat treatment depends significantly on the initial, as-printed microstructure. Overall, this study demonstrates the importance of part size, part number per build, and time intervals on DED-L process parameter selection and post-process heat treatments for achieving better quality control. [ABSTRACT FROM AUTHOR]

The crystal-chemical relationship of the cubic Laves phase MgCu2 (space group F d 3 ‾ m, cF24) with the ternary phases Cd2Cu3In, Na2Au3Al, Mg2Rh3P, Li2Pd3B, Ag2Pd3S, Cu3Pt2B, Mo3Al2C, Mo3Ni2N, and V3Ga2N (subgroup P4132, cP24, dca) is discussed based on a group-subgroup scheme. The course of the lattice parameters and the free positional parameters show substantially different distortions and thus clear differences in chemical bonding, classifying these phases as isopointal rather than isotypic (usually they are all assigned to the Mo3Al2C type). The group-subgroup scheme further shows that the β-Mn and SrSi2 structures are vacancy-ordered variants of the cP24, dca phases. The structures of Mn3IrSi and LaIrSi (space group types P213; translationengleiche subgroups) are their ternary ordered versions. [ABSTRACT FROM AUTHOR]

The quasi-binary system YbMg2-YbIn2 was studied around the equiatomic composition. In contrast to the ordered rare earth (RE) phases REMgIn (ZrNiAl type), ytterbium forms phases with different structures and pronounced Mg/In mixing (M sites). The structures of YbMg0.75In1.25 (CaLiSn type, P3m1, a = 501.95(7), c = 1087.3(2) pm, wR2 = 0.0490, 790 F2 values, 32 variables) and Yb6Mg6.41In5.59 (Yb6Ir5Ga7 type, P63/mcm, a = 1060.77(14), c = 970.27(16) pm, wR2 = 0.0484, 701 F2 values, 26 variables) were refined from single-crystal X-ray diffractometer data. YbMg0.75In1.25 is an AlB2 superstructure with a tripling of the subcell. The magnesium and indium atoms form three differently puckered layers of M6 hexagons. The Yb6Mg6.41In5.59 structure is derived from the hexagonal Laves phase YbMg2 (MgZn2 type, P63/mmc). A klassengleiche symmetry reduction leads to four crystallographically independent M sites for the rows of corner- and face-sharing tetrahedra which allow a composition close to the equiatomic one. The M–M distances in both structures cover the broad range from 289 to 331 pm, comparable to the sums of the covalent radii. Temperature dependent magnetic susceptibility studies of the polycrystalline YbMg0.75In1.25 and Yb12Mg13In11 samples indicate Pauli paramagnetism with room temperature values of 2.8(1) × 10−3 emu mol−1 (YbMg0.75In1.25) and 5.2(1) × 10−3 emu mol−1 (Yb12Mg13In11). [ABSTRACT FROM AUTHOR]

The YxNi2−yMny system was investigated in the region 0.825 ≤ x ≤ 0.95, 0.1 ≤ y ≤ 0.3. The alloys were synthesized by induction melting and corresponding annealing. The substitution of Mn for Ni (y = 0.1) favors the formation of a C15 structure with disordered Y vacancies against the superstructure of Y0.95Ni2. For y = 0.2 and 0.3, Mn can substitute in both Y and Ni sites. Single-phase compounds with a C15 structure can be formed by adjusting both the Y and Mn contents. Their hydrogen absorption–desorption properties were measured by pressure–composition isotherm (PCI) measurements at 150 °C, and the hydrides were characterized at room temperature by X-ray diffraction and TG–DSC experiments. The PCIs show two plateaus corresponding to the formation of crystalline and amorphous hydrides. The heating of the amorphous hydrides leads to an endothermic desorption at first and then a recrystallization into Y(Ni, Mn)3 and YHx phases. At higher temperatures, the Y hydride desorbs, and a recombination into a Y(Ni, Mn)2 Laves phase compound is observed. For y = 0.1, vacancy formation in the Y site and partial Mn substitution in the Ni site enhance the structural stability and suppress the hydrogen-induced amorphization (HIA). However, for a larger Mn content (y ≥ 0.2), Mn substitutes also in the Y sites at the expense of Y vacancies. This yields worse structural stability upon hydrogenation than for y = 0.1, as the mean ratio r(Y, Mn)/r(Ni/Mn) becomes larger than for y = 0.1 r(Y, ☐)/r(Ni/Mn). [ABSTRACT FROM AUTHOR]

A slab of dimension (152 × 25 × 18) mm3 is successfully fabricated through Cold Metal Transfer + Metal Inert Gas-based Wire Arc Additive Manufacturing (WAAM). 4.3 kg/h deposition rate is achieved. WAAMed Inconel 718 exhibits dendritic microstructure which grows along the build direction. In the solid solution matrix of Ni–Cr–Fe, Laves phase, Nb-rich MC-type carbides and delta (δ ) phases are detected. The average tensile strength along horizontal direction is obtained as ~ 824 MPa. Location-specific microstructure evolution causes significant extent of property anisotropy predominantly along the build direction. The horizontal tensile specimen extracted from the bottom region of the slab exhibits the highest tensile strength (UTS), while the lowest tensile strength is obtained for the specimen extracted from the middle zone of the fabricated slab. Temperature data as recorded by the thermocouples are utilized to understand the complex heat interaction phenomena during WAAM process. Laves phase is completely dissolved during homogenization treatment thus microstructure of aged specimen only consists of strengthening phase, i.e., γ ″ (Ni3Nb) and Nb-rich MC carbides. [ABSTRACT FROM AUTHOR]

Herein, Nb element is introduced into the AlCoCrFeNi2.1 eutectic high‐entropy alloy to create a heterogeneous structure. AlCoCrFeNi2.1Nbx (x = 0, 0.25, 0.5) eutectic high‐entropy alloys (HEAs) are fabricated using selective laser melting technology. The forming characteristics, microstructure, and mechanical properties of the AlCoCrFeNi2.1Nbx eutectic HEAs are investigated. The results show that the relative density of the samples increase and then decrease. The optimal process parameters are determined as laser power of 50 W, scanning speed of 400 mm s−1, scanning spacing of 70 μm, and layer thickness of 30 μm. The primary microstructure of AlCoCrFeNi2.1Nbx alloys (x > 0) consists of a hypoeutectic structure comprising body‐centered cubic, face‐centered cubic, and Fe2Nb‐type Laves phases. With the addition of Nb element, the hardness of the high‐entropy alloy increases from 600.6 to 774 HV, the yield strength increases from 664.1 to 1091.9 MPa, while the ductility slightly decreases. Furthermore, the strengthening mechanisms of the alloy are attributed to the precipitation strengthening and solid solution strengthening of the Laves phase, as well as the grain refinement effect. The wear resistance of the alloy improves gradually with the increasing Nb content, and AlCoCrFeNi2.1Nb0.5 exhibits the best wear resistance, primarily through adhesive wear. [ABSTRACT FROM AUTHOR]

This study presents the effect of stoichiometry and annealing condition on Ti–Cr AB 2 -type hydrogen storage alloys. Prior to annealing the majority phase of the as-cast alloys was the C14 Laves phase, with separate Ti and Cr phases. Annealing treatment (1273 K/14 d) led to a transition from C14 to C15 Laves phase structure. Both C14 (as-cast) and C15 (annealed) cell size increased with Ti content, up to a ratio (Cr/Ti) of 1.6, due to B-site Ti substitution in the lattice up to a limit. Pressure composition isotherm (PCI) measurements demonstrated alloys containing a greater Ti content had a better maximum hydrogen storage capacity (1.5 vs. 1.03 wt%) and lower plateau pressure (9.4 vs. 15.8 bar) at 253 K. Annealing resulted in a lower storage capacity (1.05 vs. 1.49 wt%), greater plateau pressure (ca. 30 bar) and flatter plateau slope (25 % reduction in plateau slope). Reduction in hydrogen storage capacity of annealed alloys could be due to diffusion of residual Cr in the alloy into the C15 Laves phase during the annealing process, thereby changing the local composition as confirmed through X-ray diffraction (XRD). • The C14 and C15 cell size for as cast and annealed alloys increased with Ti content. • The increase in cell size indicates (limited) Ti substitution in the lattice. • Cr vacancies are present in smaller deviations away from AB2 stoichiometry. • Greater Ti content leads to high hydrogen storage capacity and low plateau pressure. • Capacity reduces post-annealing due to C15 B-site Cr diffusion and increased oxygen. [ABSTRACT FROM AUTHOR]

Hysteresis of hydrogen storage alloys essentially hinders the compressibility and operation efficiency of metal hydride hydrogen compressors. In this work, minor Al additive was added into Ti–Cr based hydrogen compression alloys through induction levitation melting, and the apparent hysteresis was successfully ameliorated. The XRD and SEM results indicate homogeneous element distribution of a main C14 Laves phase of Ti 0.96 Zr 0.06 Cr 1.0 Mn 0.6 Fe 0.4 Al x (x = 0, 0.01, 0.02, 0.04, 0.08) alloys, and vanishing of a minor oxide phase in case the Al additive is introduced. As Al stoichiometry increases in the alloys, the hydrogenation plateau decreases obviously but the dehydrogenation plateau hardly changes. Meanwhile, the hydrogen capacity ascends initially but descends slightly. Additionally, no severe performance degradation is induced. The mechanism for overall performance improvement can be concluded as dual functions of Al additive: one can be oxide reduction of other elements during melting determined by XPS and ICP, and the other can be partial Al substitution for the B-side elements, leading to relieved deformation energy surrounding the vacant Al-containing interstitials. As to hydrogenation kinetics, the alloys exhibit accelerated hydrogenation rate with increased Al stoichiometry due to decreased activation energy and hydrogenation plateau. Furthermore, the first-principles calculation results indicate random Al substitution for the B-side atoms, and anisotropic expansion of the unit cell can be attributed to Al substitution at 6h sites. This work reveals a simple and effective way to enhance hydrogen storage performance of Ti–Cr based alloys. [Display omitted] • Influence of minor Al additive in Ti–Zr–Cr–Mn–Fe based alloys is investigated. • Hysteresis is remarkably modified by Al additive with overall enhanced performance. • Reduction and substitution dual-effect of Al is key mechanism for modification. • Results of first-principles calculation indicate random Al substitution at B-sites. • Optimum stoichiometry of Al additive should be 0.01–0.04 in the studied alloys. [ABSTRACT FROM AUTHOR]

Getter alloy has the advantages of low cost and high hydrogen purity in small and medium-scale hydrogen purification. However, the commonly used ZrMnFe alloy is reactive to various impurities in hydrogen, and requires a temperature above 600 °C to remove methane. To improve reactivity with methane and ensure a high hydrogen adsorption platform pressure, partial substitution of Fe with Ni, which has a smaller bonding energy with methane ligand, is beneficial. In this work, we prepared ZrMnFeNi alloys with different Ni stoichiometric ratios by suspension induction melting and investigated their performance in purifying hydrogen containing trace amounts of methane. All alloys maintain C14 Laves phase, and the interplanar spacing of the (103) crystal planes decreases with the replacement of Ni. It is proved that ZrMnFeNi alloys can significantly improve the absorb efficiency of methane in hydrogen and reduce the removal temperature. At 450 °C, ZrMnFe 0.7 Ni 0.3 can remove 10 ppm methane to 0.124 ppm. The purification efficiency of hydrogen at 450 °C can reach 96.94%, while the purification efficiency of ZrMnFe alloy is only 27.12%. The ZrMnFe 0.7 Ni 0.3 alloy decomposes methane into carbon and hydrogen during purification, and the carbon diffuses into the alloy at high temperature to form a metal carbide with zirconium. The XPS results show that the electron-rich state of Ni is more beneficial for activating the C–H bond breaking of methane. • Ni contents is optimized for the best hydrogen purification performance. • Purification temperature reduction and efficiency improvement attributed to Ni doping. • The ZrMnFe 0.7 Ni 0.3 can remove 10 ppm methane in hydrogen to 0.124 ppm at 450 °C. • Electron-rich Ni may be more conducive to the activation of C–H bond cleavage. [ABSTRACT FROM AUTHOR]

This study focused on assessing the crystal structure and hydrogen storage properties of two multicomponent alloys having the Zr 33 (CrMnFeNi) 67 and Zr 33 Cr 22 Mn 15 Fe 25 Ni 5 compositions. Both alloys were designed by thermodynamic calculations derived from the TiZrCrMnFeNi system after removing the titanium element from the original composition and keeping the high fraction of zirconium to explore new Zr-based compositions with a strong tendency to crystallize as a C14 Laves phase. The arc-melted Zr-based alloys exhibited a significant presence of C14 Laves phases and small amounts of NiZr intermetallic phase. Hydrogen storage properties investigated through pressure-composition-temperature (PCT) absorption and desorption isotherms revealed that the Zr 33 Cr 22 Mn 15 Fe 25 Ni 5 alloy could absorb 1.8% (H/M = 1.2) of hydrogen with fast kinetics at room temperature after a simple heat activation, while the Zr 33 (CrMnFeNi) 67 alloy could reversibly absorb 1.6% (H/M = 1) with equally fast kinetics. Zr-rich alloys exhibited a low hydrogen equilibrium pressure in the PCT isotherms. After full hydrogenation at room temperature, the initial metallic C14 Laves phases were converted to the respective Laves phase hydrides in both cases. Under cycling, the fractions of the secondary NiZr and the C14 phase change as the samples become more activated. The microstructural analysis, before and after the cycling, showed a very homogeneous microstructure and good distribution of the elements in both alloys. • Zr 33 (CrMnFeNi) 67 and Zr 33 Cr 22 Mn 15 Fe 25 Ni 5 alloys were designed for hydrogen storage. • A significant presence of C14 Laves phase with a small amount of NiZr intermetallic phase was found. • The alloys showed very fast kinetic and full reversibility at room temperature. • Zr-rich alloys exhibited a low hydrogen equilibrium pressure in the PCT isotherms. [ABSTRACT FROM AUTHOR]

The ambition of carbon neutrality has become a common pursuit for researchers worldwide, and hydrogen as a green and clean energy carrier is expected to contribute to this achievement. Since hydrogen fuel cell vehicles require a high input hydrogen pressure, compressors in hydrogen refueling stations are thus indispensable for the large-scale application of hydrogen energy. Compared to conventional mechanical hydrogen compressors, metal hydride based hydrogen compressors have the advantages of high security and low cost, providing a viable solution for hydrogen refueling station development. Herein, two series of Ti 0.95 Zr 0.07 Cr 1.3- x Mn x Fe 0.4 (x = 0.2, 0.3, 0.4, 0.6) and Ti 0.95 Zr 0.07 Cr 1.0 Mn 0.6 Fe 0.4- y Cu y (y = 0.1, 0.15, 0.2, 0.3) alloys were designed to achieve 8–22 MPa hydrogen compression in water bath at 283–353 K. All the as-prepared alloys exhibit the single hexagonal C14 Laves phase structure. In particular, the double substitution of Cr and Fe by Cu and Mn elements in Ti–Zr–Cr–Mn–Fe alloy can enlarge its hydrogen storage capacity without varying the equilibrium pressure. For instance, Ti 0.95 Zr 0.07 Cr 1.0 Mn 0.6 Fe 0.25 Cu 0.15 alloy has a hydrogenation plateau pressure of 6.16 MPa at 283 K and a dehydrogenation plateau pressure of 24.23 MPa at 353 K, with the max hydrogen capacity of 1.72 wt%. Furthermore, the relative high density molding method of metal hydride bed with 20 g of alloy powder was developed. The binder epoxy resin and the thermal conductor flake graphite were selected and added into the alloys to form metal hydride compacts (MHCs). The structural stability of modified MHCs can be enhanced due to the formation of a three-dimensional grid structure, with a higher resistance to pulverization and degradation. The improved thermal conductivity involving a filling compact strategy can significantly shorten hydrogenation reaction time by 50% and lower the abrupt temperature of metal hydride bed by 20 K with excellent stability over 100 cycles, and provide new insights of the development of safe and efficient hydride hydrogen compressor. [Display omitted] • The double substitution of Cr and Fe by Cu and Mn enhances thermodynamic hydrogen storage performance. • Optimal Ti-based alloy has de-hydrogenation plateau pressures of 24.23 MPa (353 K) and 5.74 MPa (283 K) with 1.72 wt% capacity. • A three-dimensional grid structure of epoxy resin and flake graphite is introduced to enhance the efficiency of the MHHC. [ABSTRACT FROM AUTHOR]

High Entropy Alloys (HEAs) have attracted increasing attention due to their unique characteristics, of which the lattice distortion property is particularly beneficial for hydrogen storage. Herein, we prepared the TiZrFeMnCrV HEAs with different V contents and elucidated the effect of V on the hydrogen storage properties. The TiZrFeMnCrV x (x = 0.5, 1.0, 1.5, 2.0 at%) alloys rapidly absorb 90% of their hydrogen storage capacity within 76 s at 30 °C. Among the alloys, all the three alloys TiZrFeMnCrV x (x = 1.0, 1.5, 2.0 at%) exhibit higher hydrogen absorption properties, which absorb 1.91, 1.93 and 1.91 wt% of hydrogen at 30 °C, respectively. Among them, the TiZrFeMnCrV x (x = 1.0 at%) alloy shows the best dehydrogenation performance, starting to release hydrogen at 151.33 °C and terminating at 346.36 °C. Meanwhile, the TiZrFeMnCrV x (x = 1.0 at%) exhibits remarkable cycle stability and displays a reversible gravimetric capacity of 98% after 15 cycles. [Display omitted] • Regardless of the V content, all the alloys rapidly absorb 90% of hydrogen within 76 s at 30 °C. • The higher hydrogen absorption performances of the TiZrFeMnCrV x alloy are obtained when x = 1.0, 1.5, 2.0 at%. • The maximum hydrogen storage capacity of 1.93 wt% is obtained for the TiZrFeMnCrV x (x = 1.5 at%) alloy at 30 °C. • The TiZrFeMnCrV x (x = 1.0 at%) alloy retains 98% of hydrogen storage capacity after 15 cycles at 30 °C. [ABSTRACT FROM AUTHOR]

The novel Ti 23- x V 40 Mn 37 Hf x (x = 8 and 10 at%) multi-principal element alloys (MPEAs) were prepared using vacuum non-consumable electrode arc-melting furnace. An analysis of the hydrogen sorption process unveiled a thought-provoking discovery, shedding light on the microstructure and performance of the alloys. The MPEAs exhibited a higher abundance of the C14 Laves phase in comparison to the Ti 23 V 40 Mn 37 alloy. The C14 Laves phase underwent a transformation into columnar dendrites, resulting in the formation of a finely textured eutectic structure within the MPEAs. This distinctive microstructure endowed the MPEAs with superior activity and faster hydrogen absorption kinetics compared to the Ti 23 V 40 Mn 37 alloy. The initial hydrogen absorption process followed a nucleation and crystal growth mechanism. In addition, the Ti 13 V 40 Mn 37 Hf 10 alloy exhibited an impressive maximum hydrogen desorption capacity of 1.96 wt%, representing a significant 38% increase when compared to the Ti 23 V 40 Mn 37 alloy. This enhanced hydrogen desorption capacity can be attributed to the presence of numerous diffusion channels for hydrogen atoms, as well as shorter diffusion distances within the MPEAs. Furthermore, the values of ΔH increased to 30.38 and 32.76 kJ/mol H 2 , respectively, for the MPEAs. This indicates a higher stability of hydrides within the MPEAs. • Eutectic structure (BCC + C14 Laves) is formed in the Ti 23- x V 40 Mn 37 Hf x (x = 8 and 10 at.%) alloys. • The phase abundance of C14 Laves phase increases. • The hydrogen absorption kinetic performance is improved. • The initial hydrogen absorption kinetic conforms to nucleation and crystal growth mechanism. • The max desorption capacity of increases to 1.96 wt%. [ABSTRACT FROM AUTHOR]

The ability of high-entropy alloys (HEAs) for hydrogen storage is a rather new topic in the hydrogen community. HEAs with the C14 Laves phase have shown a high potential to reversibly store hydrogen at room temperature, but most of these alloys require a high-temperature activation treatment. This study explores the role of interphase boundaries on the easy activation of HEAs at room temperature. Two chemically similar HEAs with single and dual phases, TiV 1.5 ZrCr 0.5 MnFeNi (C14 + 4 vol% BCC phases) and TiV 1.5 Zr 1.5 CrMnFeNi (single C14 phase), are designed and synthesized. While the dual-phase alloy readily absorbs hydrogen at room temperature without any activation treatment, the single-phase alloy requires a high-temperature activation. It is suggested that interphase boundaries not only provide pathways for easy hydrogen transport and activation of HEAs at room temperature but also act as active sites for heterogeneous nucleation of hydride. This study introduces interphase-boundary generation as an effective strategy to address the activation drawback of HEAs. • The interphase boundary effect on hydrogen storage in high-entropy alloys (HEAs) is studied. • Two septenary HEAs are designed for room-temperature hydrogen storage. • The BCC/C14 interphase boundaries ease activation of HEAs for hydrogen storage. • Easy activation is due to mainly fast hydrogen transport via interphase boundaries. [ABSTRACT FROM AUTHOR]

V-based BCC solid-solution alloys have been considered as promising hydrogen storage materials due to their high hydrogen storage capacity; however, the low effective hydrogen desorption capacity and high cost of pure V have limited their practical application in fuel cell vehicles or devices. Herein, a low-V TiCr 1.2 (V–Fe 0.203) 0.6 hydrogen storage alloy with a hydrogen storage capacity of 3.35 wt% has been developed by using a low-cost FeV80 as raw material. To further increase the effective hydrogen desorption capacity, cheap Mn is first used to partially substitute for Cr in FeV80-based alloy. The Mn substitution alloy achieves an effective hydrogen desorption capacity of 2.07 wt% cutting-off at 0.1 MPa with good activation performance. It is ascribed that the minor alloying of Mn increases the dehydrogenation plateau pressure and reduces the hysteresis and the enthalpy change value. The dehydrogenation enthalpy decreases from 34.84 kJ/mol to 31.51 kJ/mol. The synergistic effect of Mn and Fe increases the abundance of the C14 Laves phase, which plays a catalytic role in hydrogen absorption and desorption. The cost of TiCr 1.1 Mn 0.1 (V–Fe 0.203) 0.6 alloy is much lower than that of using pure V, and even lower than some AB 2 alloys based on cost estimation. The results of this study would provide a reference for the application of low-cost Ti–Cr-(FeV80) alloys for hydrogen storage. [Display omitted] • FeV80 was used to prepare low-V alloys to greatly reduce the cost. • The TiCr 1.2 (V–Fe 0.203) 0.6 low -V alloy with a high hydrogen storage capacity of 3.35 wt% at 298 k. • Improved effective hydrogen storage capacity of the alloys by minor Mn substitution. [ABSTRACT FROM AUTHOR]

For heat resistant alloys, long-term structural stability at high temperatures is a critical issue for alloy design and applications. In this paper, the long-term creep behaviours and structural stabilities of six heat resistant high Ni alloys and austenitic stainless steels have been studied. The longest creep rupture life is up to 359 283 hours. High Ni and Cr alloys show a good combination of high creep and oxidation resistances. Precipitation of nano MX particles with a very low growth rate improves long-term creep resistance at high temperatures. Long-term stable multiple nanoprecipitates of MX, Cu-rich, Laves and M23C6 phases can greatly contribute to the creep strength. Low Ni austenitic stainless steels show comparatively low oxidation and creep resistances. It was first found that at 800°C, Cr2N could form in the low Ni steel with a long-term crept by the absorption of nitrogen from the air into the matrix. [ABSTRACT FROM AUTHOR]

This study reports the development of a two-stage metal hydride hydrogen compressor (MHHC) capable of compressing hydrogen from 1 to 30 MPa through a temperature change between 20 and 150 °C. AB 2 -type hydrogen storage alloys in the C14 Laves phase are employed, where A = Ti and Zr and B = Cr, Mn, and V. The pressure transfer conditions between the two stages are investigated, and the composition of the AB 2 alloys is optimized accordingly: the Mn content x in Ti 0.8 Zr 0.2 Cr 1.9 − x Mn x V 0.1 and the Zr content y in Ti 1 − y Zr y Cr 1.2 Mn 0.8 , for the 1st and the 2nd stage materials, respectively. A laboratory-scale two-stage compressor is fabricated and operated using the selected alloys, whereby hydrogen is successfully compressed to 30 MPa. The compression capacity is analyzed to estimate the useable capacity of the materials. The results of this study can serve as a guide for the design and evaluation of multistage MHHCs. • A two-stage MHHC, compressing H 2 from 1 to 30 MPa in the 20–150 °C range, is reported. • AB 2 -type hydrogen storage alloys, (Ti, Zr)(Cr, Mn, V) 2 , are employed for the MHHC. • The transfer pressure from the 1st to 2nd stage is examined and optimized. • Linear coefficients to estimate the plateau pressures are derived. • The estimated useable capacities are compared with the compression capacities. [ABSTRACT FROM AUTHOR]

To investigate the comprehensive effects of the Al and Zr element contents on the microstructure evolution of the AlNbTiVZr series light-weight refractory high entropy alloys (HEAs), five samples were studied. Samples with different compositions were designated Al1.5NbTiVZr, Al1.5NbTiVZr0.5, AlNbTiVZr, AlNbTiVZr0.5, and Al0.5NbTiVZr0.5. The results demonstrated that the actual density of the studied HEA samples ranged from 5.291 to 5.826 g·cm−3. The microstructure of these HEAs contains a solid solution phase with a BCC structure and a Laves phase. The Laves phase was further identified as the ZrAlV intermetallic compound by TEM observations. The microstructure of the AlNbTiVZr series HEAs was affected by both the Al and Zr element contents, whereas the Zr element showed a more dominant effect due to Zr atoms occupying the core position of the ZrAlV Laves phase (C14 structure). Therefore, the as-cast Al0.5NbTiVZr0.5 sample exhibits the best room temperature compression property with a compression strength (σp) of 1783 MPa and an engineering strain of 28.8% due to having the lowest ZrAlV intermetallic compound area fraction (0.7%), as characterized by the EBSD technique. [ABSTRACT FROM AUTHOR]

This investigation delved into the alterations in the mechanical properties of a TiZrHfMoCrCo high-entropy alloy due to phase transformations induced by high-pressure torsion (HPT). The alloy's genesis involved levitation melting within an argon atmosphere, presenting two distinct states for analysis: the initial, post-manufacturing state and the state subsequent to HPT treatment. The original alloy featured a composition comprising a singular A2 phase with a bcc lattice and two Laves phases, C15 and C14. The HPT process triggered significant phase modifications: a retention of one C15 Laves phase and decomposition of the bcc phase into two distinct phases exhibiting different bcc lattice parameters. The HPT-induced effect prominently manifests as strong grain refinement. However, scanning electron microscopy (SEM) observations unveiled persistent inhomogeneities at a micron scale both before and after HPT treatment. Thus, grain refinement occurs separately within each of the bcc and Laves phases, visible in the light, dark, and gray areas in SEM images, while mixing does not occur on the scale of several microns. The examination of Ti, Cr, Co, Zr, Mo, and Hf via X-ray absorption spectroscopy (EXAFS) at specific K-edges and L3-edge revealed that the HPT treatment conserves the local atomic environment of metal atoms, albeit with a slight elevation in static disorder. Assessments through microhardness and three-point bending tests demonstrated the material's inherent hardness and brittleness. The microhardness, standing at a substantial value of 600 HV, displayed negligible augmentation post-HPT. However, the microhardness of individual phases exhibited a notable alteration, nearly doubling in magnitude. [ABSTRACT FROM AUTHOR]

In this study, different amounts of Nb (0–8 wt%) were added into In625 powder mixtures to prepare In625/(Nb x + SiC 0.5) composite coatings on In625 substrate by laser cladding. The effects of Nb content on the phase composition, microstructure, microhardness and wear resistance of the coatings has been comprehensively investigated. The results show that Nb can promote the precipitation of NbC, Cr 23 C 6 and Laves in the coating while refining the grains, and carbides are not only enriched at grain boundaries to play the role of pinning, but also diffuse precipitation within the grain to play the role of diffusion strengthening. The formation of more laves phases in the coating is promoted by excessive Nb content, which ultimately leads to the uneven distribution of microstructure in the coating. When the Nb content reaches 4 wt%, the NbC with uniform distribution and good adhesion with the substrate can effectively reduce the fracture and detachment of the hard phase in the abrasion process, resulting in optimal wear resistance. While the wear resistance of the coating decreases instead when the Nb content is too high. Overall, the alloying effect of Nb changes the content and distribution of reinforcing phases in the coating of In625 matrix composites, enhancing the uniformity of microstructure, resulting in an increase in the hardness and wear resistance of the coating. [ABSTRACT FROM AUTHOR]

The thermal stability of the grain structure and mechanical properties of the high-entropy two-phase TiCoCrFeMn alloy produced by powder metallurgy, assessed based on microhardness measurements, was analyzed in this work. For this purpose, material obtained via sintering using the U-FAST method was subjected to long-term heating at a temperature of 1000 °C for up to 1000 h in an argon atmosphere. For homogenization times of 1, 10, 20, 50, 100, and 1000 h, grain size changes in the identified phase components of the matrix were assessed, and microhardness measurements were conducted using the Vickers method. It has been shown that the changes in the analyzed parameters are closely correlated with non-monotonic modifications in the chemical composition. It was found that the tested alloy achieved structural stability after 100 h of annealing. A stable grain size was obtained in the BCC solid solution of approximately 2 µm and the two-phase BCC+C14 mixture of roughly 0.4 µm. Long-term heating for up to 1000 h caused the grain structure to grow to 2.7 µm and 0.7 µm, respectively, with a simultaneous decrease in hardness from 1065 HV to 1000 HV. The chromium and titanium diffusion coefficient values responsible for forming the BCC solid solution and the Laves C14 phase, including the material matrix, were also determined at this level to be DCr = 1.28 × 10−19 (m2·s−1) and DTi = 1.04 × 10−19 (m2·s−1), demonstrating the sluggish diffusion effect typical of high-entropy alloys. [ABSTRACT FROM AUTHOR]

Topologically close-packed (TCP) phases such as Laves phases are usually considered to harm the mechanical properties of classical superalloys for high-temperature applications. However, if an optimal fraction and size are designed, this situation can completely change for some compositionally complex alloys (CCA). Based on existing studies on austenitic or ferritic steels, we propose in this paper a design strategy aimed at exploiting the role of the Laves phase in defining the mechanical properties of wrought CCAs at elevated temperatures. We demonstrate its efficiency by applying it to the design and production of a new Laves phase—reinforced CCA and present the results of their experimental and theoretical investigation. The results show that a new Laves phase-reinforced CCA can have fine-grained microstructures, lower density, and superior mechanical strength at elevated temperatures while maintaining workability. These new alloys show promising properties compared to existing CCA wrought alloys and actual Ni-based superalloys. [ABSTRACT FROM AUTHOR]

We have successfully synthesized three osmium-based hexagonal Laves compounds ROs2 (R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn2-type structure (P63/mmc, No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs2, a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs2 and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs2. ROs2 Laves phases can be viewed as a stacking of kagome nets interleaved with triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity at critical temperatures, Tc, of 5.36, 4.55, and 3.47 K for ScOs2, YOs2, and LuOs2, respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of ROs2 is intricate due to multiple interacting d orbitals of Os and R. Nonetheless, the kagome-derived bands maintain their overall shape, and the Fermi level crosses a number of bands that originate from the kagome flat bands, broadened by interlayer interaction. As a result, ROs2 can be classified as (breathing) kagome metal superconductors. [ABSTRACT FROM AUTHOR]

W 0.5 Ta 0.3 MoNbVAlTi 1-x Zr x (x = 0, 0.25, 0.5, 0.75, and 1.0) high entropy alloy coatings were prepared on the surface of 45# steel in this study using a laser cladding method. The resulting data demonstrate that increasing x changed the proportion of the phases but not the type of phases. Additionally, for all HEA coatings consisting of the BCC solid solution phase, Laves phase, MC phase, and unmelted W, the content of Laves phase was gradually decreased, and the HEA coatings microstructure was gradually transitioned from equiaxed to dendritic crystals. Solid solution strengthening, precipitation strengthening, and diffusion strengthening significantly increased the microhardness of the HEA coatings. The microhardness of the coating was the highest when x = 0.25, approximately 1.1–1.4 times that of other coatings. The wear mechanism of the HEA coatings was abrasive wear, and the wear rate first decreased and then increased with increaseing x. The combined resistance of the coating to micro-cutting and brittle debonding was the strongest when x = 0.5 with maximal wear resistance. The wear rate was only 43.8–82.9% that of other coatings. The increase in Zr content and decreasing Laves phase content reduced the number of defects and the formation of unstable oxides at the phase boundaries. The stability of the oxide layer was enhanced, and the coating exhibited the best high-temperature oxidation resistance when x = 0.75, approximately 1.4–6.3 times that of the other coatings. [ABSTRACT FROM AUTHOR]

The temperature dependence of the electrical resistivity in the temperature range from 4.4 to 300 K for Ti41Zr41Ni18 (at. %) thin coatings of different crystal perfection and phase composition was studied. The coatings were deposited by magnetron sputtering with subsequent vacuum annealing in various modes ensuring the formation of several heterophase combinations, which included 1/1 and 2/1 approximation phases, a quasicrystalline icosahedral phase, a Laves phase (Ti, Zr)2Ni, and an α-Ti (Zr) solid solution. The structure before and after annealing was studied by X-ray diffractometry. It was established that coatings with a predominant content of amorphous, quasicrystalline, or approximant 2/1 phases have a temperature coefficient of resistance less than zero, while samples with a predominance of crystalline phases demonstrate characteristic metallic conductivity. The temperature dependence of the electrical resistivity of the Ti41Zr41Ni18 quasicrystalline coating turned out to be similar to the dependence in bulk samples of the Ti40Zr40Ni20 composition. The electrical resistivity of the approximant 2/1 phase with a low content of the additional Laves phase in the film has an almost constant value in the entire investigated temperature range. [ABSTRACT FROM AUTHOR]

Laves phases crystallize in simple structures and are very common intermetallic phases that can form from combinations of elements throughout the periodic table, giving a huge number of known examples. A special feature of AB2 or AB5 phases is the ability to absorb hydrogen. This study attempts to collect, systematize and summarize the knowledge about RMn2Hx (R: Tb, Gd, Ho, Dy, Er, Sm, Nd and Y) hydrides available in the literature that is mainly related to structural and magnetic transformations. Due to the enormous wealth of data, the analysis focused on hydrides with x < 4.5 H/f.u., i.e., hydrides obtained at relatively low pressure (less than a few bars). The hydrides obtained in this way can be treated as potential hydrogen stores, which undoubtedly accounts for their current attractiveness. [ABSTRACT FROM AUTHOR]

Topologically close-packed (TCP) phases such as Laves phases are usually considered to harm the mechanical properties of classical superalloys for high-temperature applications. However, if an optimal fraction and size are designed, this situation can completely change for some compositionally complex alloys (CCA). Based on existing studies on austenitic or ferritic steels, we propose in this paper a design strategy aimed at exploiting the role of the Laves phase in defining the mechanical properties of wrought CCAs at elevated temperatures. We demonstrate its efficiency by applying it to the design and production of a new Laves phase—reinforced CCA and present the results of their experimental and theoretical investigation. The results show that a new Laves phase-reinforced CCA can have fine-grained microstructures, lower density, and superior mechanical strength at elevated temperatures while maintaining workability. These new alloys show promising properties compared to existing CCA wrought alloys and actual Ni-based superalloys. [ABSTRACT FROM AUTHOR]

We have successfully synthesized three osmium-based hexagonal Laves compounds ROs2 (R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn2-type structure (P63/mmc, No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs2, a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs2 and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs2. ROs2 Laves phases can be viewed as a stacking of kagome nets interleaved with triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity at critical temperatures, Tc, of 5.36, 4.55, and 3.47 K for ScOs2, YOs2, and LuOs2, respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of ROs2 is intricate due to multiple interacting d orbitals of Os and R. Nonetheless, the kagome-derived bands maintain their overall shape, and the Fermi level crosses a number of bands that originate from the kagome flat bands, broadened by interlayer interaction. As a result, ROs2 can be classified as (breathing) kagome metal superconductors. [ABSTRACT FROM AUTHOR]

A series of five-element CoCrFeNi-Nbx (x = 0, 1, 3, 5, 7, and 9 wt%) high-entropy alloys were prepared using high-energy ball milling and discharge plasma sintering methods. Then, the effects of doping with Nb elements on the organization and properties of the CoCrFeNi HEAs were systematically investigated by tensile testing, hardness testing, and examining their micro-morphologies. The results show that with the addition of the Nb element, the lattice distortion of the alloy due to the large size of the Nb atoms causes the microstructure of CoCrFeNi HEAs to change from a single-phase FCC structure to a dual-phase structure of FCC and Laves. With the increase in the Nb content, the increase in the volume fraction of the hard and brittle Laves phase leads to the enhancement of the HEA's tensile strength, yield strength, and hardness, and a decrease in plasticity. The Nb5 alloy showed the most excellent comprehensive performance, with a tensile strength, yield strength, and plasticity of 879.1 MPa, 491.8 MPa, and 39.8%, respectively, and all the properties were improved compared with those of the HEAs obtained by the arc melting method. The increase in the hardness of the HEAs was nearly proportional to the increase in the volume fraction of the Laves phase, which was the direct cause of the increase in the hardness of the HEA. Therefore, since the Laves phase is the direct cause of the increase in HEA hardness, the doping of CoCrFeNi HEAs with Nb can significantly improve the properties of HEAs. [ABSTRACT FROM AUTHOR]

Inconel 740H superalloy is commonly used in advanced ultra-supercritical power plants since it possesses excellent strength and creep resistance. This study investigates the microstructure and mechanical properties of Inconel 740H superalloy fabricated using wire-arc additive manufacturing. The as-printed microstructure consisted of columnar γ grains with the Laves phase and (Nb, Ti)C carbides as secondary phases. The anisotropy in grain structure increased from the bottom to the top regions, while the hardness was highest in the middle portion of the build. To guide the post-heat treatment design, thermodynamic and kinetic simulations were employed to predict the temperature and time. Complete recrystallization with the Laves phase dissolution occurred throughout the build after homogenization at 1200 °C for 2 h. The peak hardness was achieved after aging at 760 °C for 12 h with the M23C6 carbides decorating the grain boundaries and γ' precipitates in the grain interior. The yield strength (655 MPa) and ductility (29.5%) in the post-heat treated condition exceeded the design targets (620 MPa, 20%). Stress rupture tests at 750 °C showed that the high-temperature performance was at par with the wrought counterparts. The fracture mode after rupture was identified to be intergranular with the presence of grain boundary cavities along with grain boundary sliding. [ABSTRACT FROM AUTHOR]

The solid solutions (SS) of the n -component (n = 2 ... 6) systems with the participation of two fundamentally different bases – (Na, K)NbO 3 (NKN) and Pb(Ti, Zr)O 3 (PZT) have been prepared by the two-stage solid-phase synthesis followed by the conventional sintering ceramic technology. Evolution trends of the structural and electrophysical parameters at such a complication of the compositions have been established. It is shown that with an increase in the number of the components in the systems, the spontaneous deformation, characterized by a uniform deformation parameter, δ, decreases, which, due to the existing correlations, leads to a decrease in the Curie temperature and an increase in the relative permittivity. The extreme "behavior" of the piezoelectric characteristics is associated with the competing influence of the permittivity and remanent polarization on them. A conclusion is made about the expediency of using the obtained results in the creation of similar materials and devices based on them. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) are among the promising candidates for the design of structural materials in advanced nuclear energy systems. The effects of Cr, V, Ta, and Ti elements and ball milling on the microstructural evolution and mechanical properties of model RHEAs were investigated. The results show that W-rich BCC1 and Ta-rich BCC2 solid solution phases were generated after a long milling duration. After high-temperature sintering, the (Cr, Ta)-rich phase associated with the Laves phase was observed in the Cr-containing model RHEAs. In addition, a high level of Ti, Ta, and V contents promoted the in situ formation of oxide particles in the alloys. Complex TiTa2O7 and Ta2VO6 oxide phases were identified by TEM, which suggests a solid-state reaction of Ti-O, Ta-O, and V-O subjected to high-energy ball milling. The oxide particles are uniformly dispersed in the BCC matrix, which can result in dispersion strengthening and the enhancement of mechanical properties. [ABSTRACT FROM AUTHOR]

FeCrAl alloy is one of potential candidates for accident‐tolerant‐fuel (ATF)‐cladding materials due to its excellent oxidation and corrosion resistance at accident temperature, combining good mechanical properties at service temperature. Alloying strategy is an important way for improving comprehensive properties of FeCrAl alloy through the precipitation of fine Laves phase. Zr alloying can stabilize the Laves phase due to its lower diffusion coefficient and solubility in body‐centered‐cubic ferrite matrix. Herein, it is found that Zr addition changes the dynamic precipitation features of Laves phase in FeCrAl alloy during high‐temperature deformation, from only one type of Fe2M (M = Nb, Mo, Ta) Laves phase to Fe2Zr combining Fe2M‐type Laves phase. The Fe2Zr‐type Laves phase precipitates dynamically first, and the interface precipitates between which with ferrite matrix creates more nucleation sites for subsequent precipitation of Fe2M Laves phase. The results can be possibly applied for alloy design and microstructure tailoring in series of FeCrAl alloys used for ATF cladding in the near future. [ABSTRACT FROM AUTHOR]

Twenty five new ternary Laves phases RET4Mg and RET4Cd (RE = rare earth element; T = Co, Ni, Cu, Pt) have been synthesized from the elements using niobium or tantalum tubes as inert crucible materials. The lattice parameters have been derived from powder X-ray diffraction data. The structures of Ce1.41(1)Co4Mg0.59(1), Dy1.10(1)Co4Mg0.90(1), LaPt4Cd, Y1.10(1)Cu4Cd0.90(1), Ca0.93(1)Cd0.07(1)Pd2 and Eu0.87(2)Cd0.13(2)Pd2 were refined from single-crystal X-ray diffractometer data. Most phases show certain degrees of RE/Mg or RE/Cd disorder. The quenched phases are assigned to the MgCu2 structure, while the annealed ones adopt the MgCu4Sn type, a translationengleiche superstructure variant of the aristotype. The annealing time has a substantial influence on the degree of ordering and is expressed in the lattice parameters, i.e. larger ones for the disordered samples. The REPt4Cd (RE = La–Nd) samples have been characterized with respect to their magnetic properties. LaPt4Cd is a diamagnet, while CePt4Cd (2.23(1) µB), PrPt4Cd (3.40(1) µB) and NdPt4Cd (3.43(1) µB) are Curie–Weiss paramagnets. The cerium compound shows a slight moment reduction. NdPt4Cd is ordered ferromagnetically at TC = 4.4(1) K. [ABSTRACT FROM AUTHOR]

Several ternary rare-earth metals containing titanium aluminum intermetallics in the RE2TiAl3 series (RE = Y, Gd–Lu) have been synthesized from the elements using arc-melting techniques. All compounds crystallize in the trigonal crystal system with rhombohedral space group R 3 m (Z = 3) and lattice parameters ranging between a = 582–570 and c = 1353–1358 pm. They adopt the Mg2Ni3Si-type structure, which is an ordered superstructure of the cubic Laves phase MgCu2 and has been observed for Al intermetallics for the first time. Tetrahedral [TiAl3] entities that are connected over all corners form a network where the empty [TiAl3] tetrahedra exhibit a full Ti/Al ordering based on the single crystal results. The Al atoms are arranged into 63 Kagomé nets, while the Ti atoms connect these nets over the triangular units. In the cavities of this three-dimensional arrangement, the RE cations can be found forming a distorted diamond-type substructure. Magnetic measurements revealed that Y2TiAl3 and Lu2TiAl3 are Pauli paramagnetic substances, in line with the metallic character. The other compounds exhibit paramagnetism with antiferromagnetic ordering at a maximum Néel temperature of TN = 26.1(1) K for Gd2TiAl3. [ABSTRACT FROM AUTHOR]

In view ol the problems ol incomplete penetration and poor perlormance in the traditional method ol welding thick plate Inconel625 alloy, plasma welding technology was used to weld 8 mm thick Inconel625 alloy, and ERNiCrMo-3 welding wire was used as the lilling material to ensure molding. The microstructure and properties ol the welded joints were analyzed via Optical Microscope (OM), Scanning Electron Microscope (SEM), universal testing machine and microhardness testing machine. The results show that the welded joint has the optimal lorming and mechanical properties under the welding current ol 230 A, welding speed ol 240 mm/min, wire feeding speed ol 1 400 mm/min and plasma gas flow ol 4 L/min. The welded joints show a c Y;-shaped morphology with a wide top and a narrow bottom. The base metal area is austenite equiaxed crystal, the weld zone is mainly composed ol line cellular crystals, and the fusion line area is coarse cellular crystals grown perpendicular to the fusion line, MC carbide and Laves phase will precipitate during the welding process. The tensile strength of the joint is the highest, which can reach 811. 36 MPa, and the Iracture ol the welded joint is ductile Iracture, The hardness ol the weld zone is the highest under all parameters. As the welding heat input increases, the overall hardness of the welded joint increases. When the current reaches 240 A and 250 A, the hardness dillerence of the welded joint is small・ [ABSTRACT FROM AUTHOR]

In this article we have investigated the phase formation behavior and hydrogen storage characteristics of TiFe 0.8 Mn 0.2 samples produced by electrode induction melting gas atomization (EIGA) as well as conventional vacuum arc-melting (VAM). TiFe (46Ti–46Fe–8Mn (wt%) with cubic, CsCl-type structure) and C14 Laves (37Ti–51Fe–12Mn (wt%) with hexagonal, MgZn 2 -type structure) phases were detected in both atomized powders and crushed ingots, the latter possessing a lower fraction of Laves phase. Microstructural characterization included electron probe micro-analysis (EPMA) and transmission electron microscopy (TEM), which evidenced the existence of a non-equilibrium Ti 2 Fe phase in the atomized powders. The formation of this additional secondary phase was attributed to the rapid cooling rate during powder manufacturing, based on earlier findings and phase formation thermodynamic calculations combined with Scheil solidification simulations. In addition, kinetics and pressure-composition isotherms (PCIs) were acquired to determine both absorption and desorption enthalpy/entropy, as well as to study the influence of the synthesis route (and hence the resulting microstructure) on kinetics, thermodynamics and reaction mechanisms of the TiFe 0.8 Mn 0.2 alloy. [Display omitted] • TiFe 0.8 Mn 0.2 atomized powders have a finer microstructure than the cast ingots. • The existence of Ti 2 Fe phase in atomized powders is revealed by TEM. • Scheil solidification simulations confirm the possible formation of Ti 2 Fe phase. • Activated atomized powders showed faster kinetics due to its finer microstructure. • The multiphase nature of atomized powders affects the thermodynamic constants. [ABSTRACT FROM AUTHOR]