Fuel claddings and guide tubes, made of zirconium alloys, exhibit in-reactor deformation which is partly due to irradiation-induced growth. At high irradiation dose, growth breakaway occurs which is associated with the appearance of c-component loops. In the past the nucleation of c-loops has been correlated to the release of iron from Laves phases under irradiation. However, recent results show that increasing the iron content in Zr-1%Nb alloys tends to decrease the c-loop density and the irradiation induced growth rate. In order to understand these discrepancies, an extensive study was performed on the M5 alloy with Atom Probe Tomography (APT) and Analytical Transmission Electron Microscopy (ATEM). Proton irradiations were carried out at three fluences, with an energy of 2 MeV at 350°C. Native β-Nb particles showed a decrease in niobium content while Laves phases underwent a uniform amorphization with a loss of iron. Small and diffuse clusters of niobium and iron were formed everywhere in the matrix after irradiation. However, no niobium-rich nano-precipitates were seen using conventional TEM contrary to what is usually found in the literature. In addition, clusters forming intensive iron-rich bands were evidenced parallel to the basal planes around Laves phases for all the studied doses (3, 5 and 8 dpa). At 3 and 5 dpa, the iron rich band location is not correlated with c-loops but at 8 dpa iron segregation is found on c-loops. It is suggested that the iron lost by Laves phases first segregates on a-loop that are aligned along the basal planes, forming these iron-rich bands. At higher doses, iron also segregates on existing c-loops. This observation proves that c-loop nucleation is not directly enhanced by iron segregation, but there seems to be an indirect link between the loss of iron from precipitates and the c-loop formation.

Understanding the oxidation behaviour of Co-based superalloys is crucial for the deployment of such alloys in high-temperature structural applications. This study explores the oxidation behaviour of four cast Co-based superalloys with varying C (0.25 or 0.5 wt%) and Si (1 or 4 wt%) contents at 800°C, 1000°C, and 1200°C for up to 100 h. Alloys with higher Si content generally exhibited lower isothermal mass gains than the low-Si variants, although the benefit depended on temperature and was accompanied by differences in the scale loss during cooling. At 800°C, an oxidation-associated Laves phase formed within surface-breaking interdendritic oxidation channels in the high-Si alloys (associated with M 12 C), consistent with reduced short-circuit transport along these pathways and the lower measured rates of isothermal mass gain. At 1000°C, Laves formation persisted but occurred as coarser particles and did not produce a measurable separation in mass gain. Notably, the high-Si alloys exhibited increased oxide spallation during cooling from this temperature. At 1200°C, the high-Si alloys developed a more continuous silica subscale at the alloy-oxide interface, consistent with a modest reduction in isothermal mass gain relative to the low-Si alloys. For alloys with equivalent Si content, reduced C improved mass-gain behaviour at 800°C and 1200°C, consistent with a reduced extent of interdendritic network (greater interdendritic spacing), whereas at 1000°C all alloys exhibited broadly similar mass gains. These findings demonstrate that Si and C influence oxidation through coupled effects on scale constitution, microstructurally controlled transport and oxide-scale integrity, providing guidance for the design of next-generation high-temperature alloys. • 4 wt% Si alloys showed superior oxidation resistance to 1 wt% Si counterparts • Oxidation at 800°C formed Laves phase; oxidation at 1200°C gave a silica sub-scale • Quantified oxide scale thickness at 800°C supports the proposed mechanism • 4 wt% Si alloys showed shallower oxidised channel depths at all test temperatures

The segregation of brittle Laves phases remains a critical bottleneck limiting the performance of additive manufacturing (AM) nickel-based superalloys. While its evolution is governed by complex transient physical fields within the melt pool, a quantitative kinetic correlation between processing parameters and microstructural features is currently lacking. In this study, a high-fidelity multiphysics numerical model was developed to establish a cross-scale mapping logic of "Process-Physical Field-Microstructure" by dissecting the global distribution of temperature gradient (G) and solidification rate (R) along the quasi-steady-state melt pool boundary. It is revealed that increasing the scanning speed synergistically enhances R while compressing G. Beyond driving a transition from oriented columnar dendrites to refined mixed-dendritic structures, this shift effectively blocks the continuous enrichment channels of Nb and Mo elements by compressing the "kinetic time window" for solute redistribution. Consequently, the morphology of the Laves phase is forced to evolve from a continuous interconnected chain-like network into dispersed isolated particles. This research clarifies the kinetic essence of microstructural evolution under non-equilibrium solidification, providing critical physical criteria for the precise intervention of deleterious phases and the regulation of microstructural consistency in high-performance AM components.

High-strength stainless steels are essential materials for critical load-bearing aerospace components, and solution treatment serves as a core process governing their strength–toughness balance. However, in novel multi-element alloy systems, the complex dissolution behavior of precipitates and its underlying mechanisms affecting matrix phase transformations require further investigation. This study systematically explores the thermodynamic evolution and microstructural response of a novel Fe-Ni-Cr-Mo-Al-Ti ultra-high-strength stainless steel during solution treatment. The research highlights how solution temperature drives Laves phase dissolution, controls prior austenite grain growth, redistributes local chemical elements, and dictates retained austenite stability. By establishing the relationship between microstructural features and macroscopic properties, this study aims to provide crucial theoretical guidance for optimizing heat treatment protocols to achieve superior comprehensive mechanical properties in advanced high-strength stainless steels.

Laves phases composed of two-dimensional (2D) Laves tilings are prevalent in condensed matter systems, yet the existence of these 2D tilings as isolated structural motifs has remained unverified. Here, we report the discovery of a metastable, confined 2D Laves tiling precipitate in a compositionally dilute Mg alloy, revealed through aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) in combination with atomic-resolution energy-dispersive X-ray spectroscopy (EDS) mapping. The structure adopts a Laves-type Al2Ca configuration confined to the (0001) basal plane of the Mg matrix, with a thickness of merely a single tiling layer (~4.62 Å), stabilized by adjacent Mg/Ca interfacial atomic layers. Theoretical calculations reveal that tensile strain in the surrounding matrix suppresses the diffusion of small-sized Al solutes, thereby inhibiting out-of-plane coarsening. Notably, prolonged thermal exposure leads to the formation of multi-configurational layered Laves structures assembled from these fundamental units. These findings elucidate the precipitation behavior in Mg-Al-Ca alloys and uncover a structurally confined Laves tiling motif, advancing our understanding of Laves phase formation and solute clustering in metallic systems.

Nickel-based superalloy GH3625 is widely used in extreme environments due to its exceptional high-temperature strength and corrosion resistance; however, optimizing its comprehensive performance through precise microstructural control remains a critical challenge. In this study, the effect of withdrawal rate (10-200 μm/s) on the microstructural evolution, mechanical properties, and corrosion resistance of GH3625 alloy was investigated using a liquid-metal-cooled directional solidification system. The microstructural characteristics, elemental segregation, and phase distributions were systematically analyzed via OM, SEM, and EDS, followed by uniaxial tensile and electrochemical polarization tests. The results show that with increasing withdrawal rate, the solid-liquid interface morphology evolves from cellular to cellular-dendritic and finally to fully dendritic. Correspondingly, the primary dendrite arm spacing decreases from 270.4 μm to 100.2 μm, and the secondary dendrite arm spacing decreases from 66.5 μm to 12.3 μm. The area fraction of the detrimental Laves phase first decreases and then increases, reaching a minimum at 100 μm/s. Correspondingly, the yield strength increases from 282 MPa to 409 MPa, and the corrosion resistance is optimized at 100 μm/s. The microstructure-property relationships are discussed based on second-phase strengthening theory and microstructural refinement. This study provides a theoretical basis and practical process windows for optimizing directional solidification parameters to achieve enhanced mechanical and corrosion performance in GH3625 alloy.

High-throughput calculations to develop high-entropy alloys for hydrogen storage applications

Low lattice mismatched nano-precipitates in die steels

The effect of Cr content on the oxidation behavior of Nb-modified Al2O3-forming ferritic stainless steels was investigated. All alloys formed an Al2O3 scale regardless of Cr content, and the Al2O3 scale had a duplex structure, with the outer layer containing Fe and Cr and the inner layer containing relatively pure Al rich oxide. The growth rate of the outer oxide scale increased with decreasing Cr content for shorter oxidation times because of the formation and growth of a Fe-rich oxide scale for the low-Cr alloys and because of a Cr-rich oxide scale for the high-Cr alloys. However, the growth rate of the inner Al-rich oxide scale increased with increasing Cr content. For longer oxidation periods, the oxidation kinetics of the inner oxide layer formed on low-Cr alloys decreased greatly owing to the formation of a Laves phase (Fe2Nb) at the scale/alloy interface.

Critical Role of Highly Malleable Laves Phase on the Structure-Property Correlation in High Entropy Alloys

Abstract The exploration of high- T c superconducting hydrides at ambient pressure is significant for the field of physics and materials science. Herein, by employing hydrogen-storage alloys as the template, we incorporate quasi-molecular H 2 units into binary Laves phase alloy Fd 3 m - A 2 X , thereby achieving robust electron-phonon coupling at significantly reduced pressures. Through high-throughput screening of Fd 3 m - A 2 X H 16 ( A = group IIA elements, X = group IIIB elements), we identify eight dynamically stable compounds within 150 GPa. Among these candidates, Mg 2 AcH 16 is dynamically stable at 20 GPa, and Ca 2 AcH 16 maintains dynamic stability at ambient pressure. Our calculations demonstrate that charge transfer occurs from A and X atoms to the antibonding orbitals of elongated H 2 units (with H-H bond lengths from 0.85 to 0.96 Å), which concurrently activates mid-frequency H-dominated phonon modes that dominate electron-phonon coupling strength. Notably, Mg 2 AcH 16 exhibits a superconducting transition temperature of 221 K at 70 GPa (λ = 5.17 and quality factor S = 4.34). Ca 2 AcH 16 has a T c of 165 K at 95 GPa. Our work advances the fundamental understanding of high temperature superconductors and provides a viable strategy for further discovery of high temperature superconductors at ambient pressure.

Coupling Nb-tailored eutectic Laves phase load-bearing and composite oxide lubrication in Fe-Al-Nb alloys: Achieving superior wear resistance across a broad temperature range

Mechanical property restoration in embrittled ultra-super ferritic stainless steels through Laves phase redissolution

Achieving compressive plasticity in CrMoNb multi-principal element alloy by Ti addition for excellent strength-plasticity synergy at room and high temperatures

Microstructure-controlled mechanical behavior of autogenous laser-welded IN625-AISI 304L dissimilar joints

Effects of palladium substitution on structural evolution and electrochemical properties of BCC solid solution alloys coexisting with Laves phase

This study provides new insights into the microstructure and early stages of surface oxidation behavior of an equiatomic TiNbCr multi-principal element (MPE) alloy in both as-cast and hot isostatic pressing (HIP) processed conditions. The alloy comprises two phases: a Nb-rich body-centered cubic (BCC) matrix and Cr-rich Laves phase (C15) precipitates, with a reduction in Laves phase fraction observed at increasing temperatures. Dilatometry tests revealed the precipitation of a Ti-rich hexagonal close-packed (HCP) phase, particularly at a cooling rate of 10°C/min. Anisothermal oxidation tests in air were conducted to compare the early oxidation behavior of the MPE alloy with alloy 188. Notably, the as-cast condition exhibited a lower mass gain/area than the HIPed condition, attributed to the thinner Laves precipitates in the former. Furthermore, the TiNbCr alloy demonstrates a prolonged duration to achieve supersaturation and initiate oxide scale formation compared to alloy 188, with the surface oxidation process driven by the cooperative interaction between the Nb-rich BCC matrix and Cr-rich Laves phases.

Effect of Laves phase on hydrogen storage properties of BCC Ti-V-Nb–Cr–Mn high entropy alloys

Novel Nb-rich high entropy alloys strengthened by Laves phase for high-temperature applications

Refractory high-entropy alloys (RHEAs) have garnered attention for their exceptional high-temperature mechanical properties, making them suitable for aerospace and energy applications. However, balancing strength and ductility remains a challenge due to the presence of Laves phases. In this study, Al0.5Nb0.5TiV2Zrx (x = 0–2.0) alloys were prepared using vacuum arc melting, and their microstructural evolution and mechanical properties were analyzed. At room temperature, the Al0.5Nb0.5TiV2Zr0.5 alloy exhibits the highest yield strength (1658.1 MPa), which is primarily attributed to strong lattice distortion induced by Zr and moderate precipitation strengthening from Laves phases. In contrast, at higher Zr contents, excessive Laves phase precipitation promotes stress concentration, leading to a marked reduction in both strength and ductility. High-temperature compression tests revealed that the Al0.5Nb0.5TiV2Zr0.5 and Al0.5Nb0.5TiV2Zr1.5 alloys still exhibited over 50% compressive plasticity at 800 °C and 1000 °C. However, when the temperature reached 1000 °C, the instability of the Laves phase led to a reduction in the yield strength to below 160 MPa, indicating that the effect of solid-solution strengthening was no longer significant under high-temperature conditions. These findings clarify the critical role of Zr content and temperature in governing the microstructural and mechanical evolution of the Al–Nb–Ti–V–Zr system and provide a theoretical basis for achieving an optimized strength–ductility balance in RHEAs through compositional control.