In supercooled liquids, phase selection is governed by competing transformation timescales, yet crystallization typically pre-empts access to metastable liquid states. Liquid–liquid phase separation (LLPS) has long been proposed as a fundamental source of mesoscale heterogeneity, yet direct experimental access to heating-induced LLPS has remained elusive. Here we demonstrate that ultrafast heating opens a kinetic window in which crystallization and liquid–liquid demixing become temporally separable. Using a model supercooled metallic liquid, we directly resolve the emergence and growth of coexisting liquid populations on millisecond timescales by correlating ultrafast calorimetry with nanoscale real-space imaging and reciprocal-space structural probes. We show that subtle endothermic signatures in the supercooled regime—previously attributed to relaxation phenomena—constitute thermodynamic fingerprints of LLPS. The resulting chemical partitioning preconfigures subsequent crystallization pathways, revealing how competing timescales govern access to hidden regions of the liquid free-energy landscape. Our results establish kinetic control as a general route to reveal metastable liquid–liquid coexistence that is otherwise masked by crystallization, providing a framework for understanding non-equilibrium phase selection in supercooled liquids.

Magnesium alloys present a compelling prospect for absorbable implant materials in orthopedic and trauma surgery. This study evaluates an ultra-high purity, lean magnesium-calcium alloy (X0), both with and without plasma electrolytic oxidation (PEO) surface modification, in comparison to a clinically utilized WE43 magnesium alloy. It is shown that the mechanical properties of X0 can be tuned to yield a high-strength material suitable for bone screws (with an ultimate tensile strength of 336 MPa) or a ductile material appropriate for intraoperatively deformable plates (with an elongation at fracture of 24 %). Four plate-screw combinations were implanted onto the pelvic bones of six sheep without osteotomy for 8 weeks. Subsequent analysis utilized histology, microcomputed tomography, and light and electron microscopy. All implants exhibited signs of degradation and hydrogen-gas evolution, with PEO-coated X0 implants demonstrating the least volume loss and the most substantial new-bone formation on the implant surface and surrounding cancellous bone. Furthermore, the osteoconductive properties of the X0 implants, when uncoated, exceeded those of the uncoated WE43 implants, as evidenced by greater new-bone formation on the surface. This osteoconductivity was amplified with PEO surface modification, which mitigated gas evolution and enhanced osseointegration, encouraging bone apposition in the cancellous bone vicinity. These findings thus indicate that PEO-coated X0 implants hold substantial promise as a biocompatible and absorbable implant material.

Magnesium-based alloys are excellent materials for temporary medical implants, but understanding and controlling their corrosion performance is crucial. Most nanoscale corrosion studies focus on the surface, providing only 2D information. In contrast, macro- and microscale X-ray tomography offers representative volume information, which is, however, comparatively low in resolution and rather qualitative. Here a new mesoscale approach overcomes these drawbacks and bridges the scale gap by combining 3D measurements using ptychographic X-ray computed tomography (PXCT) with electron microscopy. This combination allows to observe the corrosion progress non-destructively in 3D and provides high-resolution chemical information on the corrosion products. A medical Mg-Zn-Ca alloy is used and compared the same sample in the pristine and corroded states. With PXCT an isotropic resolution of 85 and 123 nm is achieved for the pristine and corroded states respectively, which enables to distinguish nanoscale Mg2Ca precipitates from the matrix. The corroded state in best approximation to the in situ conditions is imaged and reveals the complexity of corrosion products. The results illustrate that the corrosion-layer is dense and defect-free, and the corrosion of the material is grain-orientation sensitive. The developed workflow can advance research on bioactive materials and corrosion-sensitive functional materials. Magnesium alloys are ideal for temporary implants, but understanding their biodegradation is vital. Existing studies offer limited high-resolution 2D or low-resolution 3D data. The researchers combined 3D ptychographic X-ray computed tomography and 2D electron microscopy to observe corrosion in a medical Mg alloy in 3D with high-resolution chemical detail, closely approximating in situ conditions. image

Coherent Al3X-type L12-structured dispersoids have the potential of effectively stabilizing the grain structure and increasing strength. This concept has been successfully demonstrated for non-hardenable and rapidly solidified Al alloys. In precipitation-hardened Al alloys, effective dispersoid addition requires both controlling their hightemperature stability and minimizing their impact on precipitation hardening. The current study focuses on dispersoid-modified AlZn5.0Mg1.2 alloys, which exhibit MgZn precipitation upon age-hardening and include less than 1 wt% of Zr and Hf for dispersoid formation. Heat treatments between 350 degrees C and 500 degrees C for varying times were applied to evaluate dispersoid formation, thermal stability and the related strengthening potential. The microstructure was assessed using transmission electron microscopy (TEM) and atom probe tomography (APT), and the mechanical response was evaluated by hardness testing. TEM after heating at 500 degrees C reveals Ostwald ripening for the dispersoids. APT results on the dispersoids reveal a core-shell structure development upon longer annealing times. The Zr-Hf-modified alloy exhibits a higher initial strength than the Zr-modified alloy but the latter displays greater strength retention even after prolonged exposure to 500 degrees C. This effect is attributed to a destabilization of the mixed Zr-Hf dispersoids that arises from lower enthalpic benefits of Al3Hf formation over Al3Zr.

High-performance ultra-lean binary Mg–Ca alloys are engineered by intelligent alloying and thermo-mechanical processing using hot-extrusion. With Ca-alloying contents as low as 0.2-0.6 wt.%, remarkable room-temperature tensile properties are obtained with tensile strength values as high as 380–420 MPa, or ductility values reaching a maximum of 36 %. By means of multiscale structural and chemical analysis using electron microscopy and energy dispersive X-ray spectroscopy, we show that multimodal strengthening mechanisms can be activated by modifying the spatial distribution of Ca as secondary phase. Our results indicate that strong precipitation strengthening is achieved when Mg2Ca phase particles are dispersed within the grains. On the other hand, preferential distribution of the Mg2Ca precipitates along grain boundaries imparts substantial grain-boundary strengthening by the Hall-Petch effect. Apart from secondary-phase precipitation, the role of Ca as solute atoms is paramount in promoting homogeneous deformation. The presence of Ca directly alters the intrinsic stacking fault energies and modifies the cross-slip energy barriers such that the slip-transition probability from pyramidal-to-basal and vice-versa becomes comparable. Both effects ensure competitive activation of basal and non-basal slip, thereby reducing the mechanical anisotropy. The mechanical performance in the current work, when compared to earlier reported studies of Mg alloys with similar or higher alloying content, shows a 2 to 10-fold increase in tensile strength without compromising ductility.

Electrodeposition is a versatile method for synthesizing nanostructured films, but controlling the morphology of films containing two or more elements requires a detailed understanding of the deposition process. We used liquid cell transmission electron microscopy to follow the electrodeposition of PtNi nanoparticle films on a carbon electrode during cyclic voltammetry. These in situ observations show that the film thickness increases with each cycle, and by the fourth cycle, branched and porous structures could be deposited. Synchrotron studies using in situ transmission X-ray microscopy further revealed that Ni was deposited in the oxide phase. Ex situ studies of bulk electrodeposited PtNi nanoparticle films indicated the number of cycles and the scanning rate were the most influential parameters, resulting in a different thickness, a different homogeneity, a different nanoparticle size, and a different surface structure, while the precursor concentration did not have a significant influence. By varying the potential range, we were able to obtain films with different elemental compositions.

In the quest of radiation and oxidation-resistant materials for the fuel claddings of nuclear power stations, chromium (Cr) emerges as a good candidate. It shows a significantly lower irradiation-induced swelling rate of nearly an order magnitude lower than other body-centered cubic materials, such as W and Fe. This phenomenon indicates that there is an unsuspected aspect, beyond the crystal structure that affects the swelling of materials. To understand it, the structure and distribution of irradiation-induced dislocation loops in Cr were investigated after ion irradiation at 550 ℃ from 0.1 to 15 dpa. It appears that after irradiation Cr exhibits nested loops, either vacancy-type loops called ‘trough’ or interstitial-type loops called ‘island’, which are composed of a large dislocation loop containing multiple small and coplanar loops with inverse nature. Our results indicate that the nested trough and island dislocation loops stem from the 1D migration of dislocation loops. This loop formation mechanism is an alternative mechanism of recombination and annihilation of point defects, which in turn can explain the low swelling rate in Cr. This mechanism provides a new insight into the irradiation-induced swelling rate of metals.

Micro-alloying strongly affects the incubation period of void swelling in irradiated face-centered cubic materials. However, the underlying mechanism, which relates to the formation of dislocation loops, is still unclear. Here, we investigate pure Ni, Ni-0.4wt.%Cr and Ni-0.4/0.8/1.2wt.%Ti as model materials, to gain insight into the solute effects on the loops evolution in the early stage of irradiation. The dislocation loop characteristics (mobility, Burgers vector, nature) are studied using in-situ transmission electron microscopy and ex-situ irradiation with Ni+ ions at 450°C and 510°C for doses from 0.06 to 0.7 dpa. It appears that a tiny amount of Ti effectively increases the loop density, reduces the loop mobility and the stacking fault energy. It leads to an equal distribution among a/2<110> perfect loop families. It also stabilizes self-interstitial loops against vacancy loops depending on Ti content and temperature. Our modeling of radiation-induced segregation, based on experiments and recent ab initio calculations of flux couplings, predicts a Cr enrichment and a Ti depletion nearby dislocation loops. It is in good agreement with our observations by X-ray spectroscopy in TEM and by atom probe tomography. However, the lowered loop mobility must be the signature of a thermal segregation rather than the impact of radiation-induced depletion. Indeed, oversized Ti atoms subsequently trapped at strained lattice sites around the dislocation line of the loop due to thermal segregation would inhibit its diffusion. This opens new perspectives for future experimental investigations and radiation-effect modeling.

Fe-based bulk metallic glasses (BMGs) universally show an anomalously low coefficient of thermal expansion below their Curie temperature. This effect is known as the Invar effect, is rarely seen in crystalline materials and also vanishes after the crystallization of BMGs. While it is known that Co and Ni reduce the strength of the Invar effect, the influence of other elements is unknown. Moreover, it is unclear to what extent structural modifications and magnetic interactions of minor alloying elements contribute to the Invar effect. Using synchrotron-based in-situ X-ray diffraction, we show that (Fe71B24RE5)96Nb4 BMGs with the rare earth elements (RE) = Tm, Er, Ho also reveal the Invar effect. This can be seen in the diffraction peaks that shift in accordance with the macroscopically measured thermal expansion. In comparison to a similar FeBYNb BMG, the Invar effect is not influenced by the substitution of Y with RE. This suggests that the minor alloying elements do not contribute to the Invar effect. Neither their influence on the atomic arrangement, the (anti)ferromagnetic interactions of the 4f electrons of the RE elements nor paramagnetic interactions such as those from Y and Nb have an influence on the Invar effect. These elements only serve to increase the glass-forming ability and the formation of a disordered Fe network but do not contribute themselves to the Invar effect. Additionally, their (anti-)ferromagnetic interaction with Fe does not influence the magneto-structural correlations of the Fe network. Therefore, the Invar effect in these materials not only originates at the atomic scale but can be attributed solely to the magnetic interaction in the disordered Fe network.

Fe-Cr is a model alloy for ferritic steels used in thermal power generation systems and envisaged as primary structural material for future fusion reactors. However, upon heating and, further, under irradiation, Fe-Cr can suffer from phase decomposition leading to the formation of Fe-rich and Cr-rich regions that induce simultaneous hardening and embrittlement. In this study, we examine the origins of the degradation in mechanical properties by performing room-temperature in situ micropillar compression tests on single-crystalline Fe-40wt.%Cr alloys in solid solution, and in the spinodally decomposed state obtained after annealing at 500 degrees C for 1008 and 2016 h, respectively. The compressed micropillars are subjected to correlative nanoscale structural characterization using transmission electron backscattered diffraction and transmission electron microscopy. Dislocation slip occurs unequivocally on the {110}(11 over bar 1) slip system for all conditions. While the 2016 h annealed state exhibits a more evolved nanoscale phase modulation than the 1008 h annealed condition, both microstructures display approximately double the yield strength of the solid-solution state without any concurrent loss of ductility. Our findings reveal a fundamental change in plasticity mechanism across the three different microstructures. Deformation in the solid-solution state is associated with kink-mediated local plasticity occurring on multiple glide systems, which activate sequentially based upon the largest instantaneous Schmid factor. This gradually transforms into a less localized Luders-band like plasticity associated with single-slip activation in the 1008 h annealed state, while the deformation in the 2016 h annealed state is marked by uniform strain hardening related to a homogeneous polycrystalline-like dislocation motion occurring simultaneously on multiple slip systems. Correlations between the spatial and compositional fluctuations in Cr and the associated plasticity dynamics are established. It is shown that the spatial fluctuations in Cr strongly influence dislocation strengthening and the relative mobility of the edge and screw components across all microstructural states. It is further concluded that the phase-separation effect, despite promoting strengthening, does not act as the primary cause of embrittlement, but rather plays a contrary role of enhancing ductility.

Electrocatalysis offers great promise for water purification but is limited by low active area and high uncontrollability of electrocatalysts. To overcome these constraints, we propose hybrid bulk electrodes by synthesizing and binding a Pd nanocatalyst (nano-Pd) to the electrodes via amyloid fibrils (AFs). The AFs template is effective for controlling the nucleation, growth, and assembly of nano-Pd on the electrode. In addition, the three-dimensional hierarchically porous nanostructure of AFs is beneficial for loading high-density nano-Pd with a large active area. The novel hybrid cathodes exhibit superior electroreduction performance for the detoxification of hexavalent chromium (Cr 6+ ), 4-chlorophenol, and trichloroacetic acid in wastewater and drinking water. This study provides a proof-of-concept design of an AFs-templated nano-Pd-based hybrid electrode, which constitutes a paradigm shift in electrocatalytic water purification, and broadens the horizon of its potential engineered applications.

While lean Mg-Zn-Ca alloys are promising materials for temporary implants, questions remain on the impact of Zn and Ca on the microstructure. In this context, the precipitation of Zn and Ca in Mg-1.5Zn-0.25Ca (in wt.%), initially extruded at 330 & DEG;C, towards Mg-Ca binary precipitates or Ca-Mg-Zn ternary precipitates was probed in a multiscale correlative approach using atom probe tomography (APT) and an-alytical transmission electron microscopy (TEM). Particular focus was set on the ternary precipitate phase whose structure is debated. In the as-extruded material, the binary precipitates are made of hexagonal C14 Mg2Ca containing up to about 3 at.% of Zn. The ternary ones are based on the hexagonal Ca2Mg5Zn5 prototype structure with a composition close to Ca3Mg11Zn4, as deduced from atomically resolved EDS mapping and scanning TEM imaging, supported by simulations. The precipitation sequence was scru-tinized upon linear heating from room temperature to 375 ?, starting from the solutionized material. Three exothermic differential scanning calorimetry (DSC) peaks were observed, at respectively 125, 250 and 320 & DEG;C. Samples were taken after the peak decays, at respectively 205, 260 and 375? for structural analysis. At 205 & DEG;C, APT analysis revealed Ca-rich, Zn-rich and Zn-Ca-rich clusters of about 3 nm in size and with a number density of 5.7 x 10 23 m -3. At 260 ?, APT and TEM showed mono-layered Zn-Ca-rich Guinier-Preston (GP) zones of about 8 nm in size and with a number density of 1.3 x 10 23 m -3. At 375 ?, larger and highly coherent elongated precipitates were found, with a size of about 50 nm. They occur as binary Mg-Ca precipitates or ternary Ca2Mg6Zn3 precipitates, as deduced from scanning TEM-based energy dispersive X-ray spectroscopy (EDS) and nanodiffraction in TEM. Here, the binary precipitates outnumber the ternary ones, while in the as-extruded material the ternary precipitates outnumber the binary ones, which corresponds well to the calculated phase diagram. We correlated the microstruc-ture to hardness probed by Vickers testing. The largest hardening relates to the end of the 125 ? DSC peak and thus to GP zones, which outperform the hardening induced by the nanometer-sized clusters and the larger intermetallic particles. The complexity of the precipitation sequence in lean Mg-Zn-Ca alloys is discussed.(c) 2022 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

The Invar effect is universally observed in Fe-based bulk metallic glasses. However, there is limited understanding on how this effect manifests at the atomic scale. Here, we use in-situ synchrotron-based high-energy X-ray diffraction to study the structural transformations of (Fe71.2B24Y4.8)96Nb4 and (Fe73.2B22Y4.8)95Mo5 bulk metallic glasses around the Curie temperature to understand the Invar effect they exhibit. The first two diffraction peaks shift in accordance with the macroscopically measured thermal expansion, which reveals the Invar effect. Additionally, the nearest-neighbor Fe-Fe pair distance correlates well with the macroscopic thermal expansion. In-situ X-ray diffraction is thus able to elucidate the Invar effect in Fe-based metallic glasses at the atomic scale. Here, we find that the Invar effect is not just a macroscopic effect but has a clear atomistic equivalent in the average Fe-Fe pair distance and also shows itself in higher-order atomic shells composed of multiple atom species.

Journal Article Nanoscale Clusters and Heterogeneities in Engineering and Amorphous Alloys Get access Stephan SA Gerstl, Stephan SA Gerstl ETH Zurich, Laboratory for Materials Physics & Technology, Dept. Materials, Zurich, SwitzerlandETH Zurich, Scientific Center for Optical & Electron Microscopy, Zurich, Switzerland Corresponding author: gerstls@ethz.ch Search for other works by this author on: Oxford Academic Google Scholar Robin Schäublin, Robin Schäublin ETH Zurich, Laboratory for Materials Physics & Technology, Dept. Materials, Zurich, SwitzerlandETH Zurich, Scientific Center for Optical & Electron Microscopy, Zurich, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Jörg Löffler Jörg Löffler ETH Zurich, Laboratory for Materials Physics & Technology, Dept. Materials, Zurich, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 712–713, https://doi.org/10.1017/S1431927622003312 Published: 01 August 2022

Magnesium-based alloy WE43 is a state-of-the-art bioresorbable metallic implant material. There is a need for implants with both complex geometries to match the mechanical properties of bone and refined microstructure for controlled resorption. Additive manufacturing (AM) using laser powder bed fusion (LPBF) presents a viable fabrication method for implant applications, as it offers near-net-shape geometrical control, allows for geometry customization based on an individual patient, and fast cooling rates to achieve a refined microstructure. In this study, the laser–alloy interaction is investigated over a range of LPBF-relevant processing conditions to reveal melt-pool dynamics, pore formation, and the microstructure of laser-melted WE43. In situ X-ray imaging reveals distinct laser-induced vapor depression morphology regimes, with minimal pore formation at laser-scan speeds greater than 500 mm/s. Optical and electron microscopy of cross-sectioned laser tracks reveal three distinct microstructural regimes that can be controlled by adjusting laser-scan parameters: columnar, dendritic, and banded microstructures. These regimes are consistent with those predicted by the analytic solidification theory for conduction-mode welding, but not for keyhole-mode tracks. The results provide insight into the fundamental laser–material interactions of the WE43 alloy under AM-processing conditions and are critical for the successful implementation of LPBF-produced WE43 parts in biomedical applications.

Binary Fe–Cr alloys are model alloys for ferritic steels proposed as structural materials for future fusion reactors. They are used to investigate the fundamental mechanisms of their degradation induced by heat and irradiation. Fe–Cr presents a miscibility gap, which induces Cr‐rich (α′) regions in an Fe‐rich (α) matrix. As this causes embrittlement, it is crucial to understand this phase decomposition and its role, starting with the heat impact. Fe–Cr alloys with 5−40 wt% Cr were annealed at 500 °C for up to 1008 h. The microstructure was probed by chemical mapping using scanning transmission electron microscopy with energy‐dispersive X‐ray spectroscopy (EDS) and atom probe tomography, and hardness was assessed by Vickers testing. Increasing Cr content increases hardness, and beyond 15 wt% Cr it further increases upon annealing. At 20 wt% Cr, nanoscale globular α′ precipitates appear, while at 40 wt% Cr an α′‐percolating structure develops. In both cases, the α′ core composition reaches slightly more than 80 at% Cr, and hardness doubles. A unified relationship is found between the alloy strength and the α′ structure and it is shown that this type of hardening is a general mechanism for mature systems, independent of the nominal alloy composition.

Magnetization structures in magnetic materials are usually imaged in dedicated Lorentz transmission electron microscopes. Compared to conventional transmission electron microscopes, the magnetic field of the objective lens at the sample is removed by replacing the objective lens with a Lorentz lens below the sample. While this modification is critical for soft-magnetic materials whose magnetic state is affected by the strong magnetic field of the objective lens, we propose that this is not necessary for permanent magnets such as Sm–Co and Nd–Fe–B. Conventional and Lorentz microscopes are compared for imaging divergent and convergent domain walls in a Sm(Co,Fe,Cu,Zr)7.7 magnet. Both techniques provide an almost identical resolution and accuracy in the measurement of the domain-wall width parameter using focal-series imaging of divergent domain walls. It is further demonstrated that both techniques can be utilized to analyze the intensity profile of convergent domain walls. From this, the product of sample thickness and magnetic induction is extracted. These results illustrate that conventional microscopes can be used to image the magnetic state of permanent magnets with a resolution comparable to dedicated Lorentz microscopes, which make magnetic imaging experiments significantly more accessible to a wider scientific community.