Search

An atomic‐scale understanding of how electrocatalyst surfaces reconstruct and transform during electrocatalytic reactions is essential for optimizing their activity and longevity. This is particularly important for the oxygen evolution reaction (OER), where dynamic and substantial structural and compositional changes occur during the reaction. Herein, a multimodal method is developed by combining X‐ray fine structure absorption and photoemission spectroscopy, transmission electron microscopy, and atom probe tomography with electrochemical measurements to interrogate the temporal evolution of oxidation states, atom coordination, structure, and composition on Co2MnO4 and CoMn2O4 cubic spinel nanoparticle surfaces upon OER cycling in alkaline media. Co2MnO4 is activated at the onset of OER due to the formation of ≈2 nm Co‐Mn oxyhydroxides with an optimal Co/Mn ratio of ≈3. As OER proceeds, Mn dissolution and redeposition occur for the CoMn oxyhydroxides, extending the OER stability of Co2MnO4. Such dynamic dissolution and redeposition are also observed for CoMn2O4, leading to the formation of less OER‐active Mn‐rich oxides on the nanoparticle surfaces. This study provides mechanistic insights into how dynamic surface reconstruction and transformation affect the activity and stability of mixed CoMn cubic spinels toward OER. [ABSTRACT FROM AUTHOR]

Dopant‐induced microstructure in thermoelectric materials significantly affects thermoelectric properties and offers a potential to break the interdependence between electron and phonon transport properties. However, identifying all‐scale dopant‐induced microstructures and correlating them with thermoelectric properties remain a huge challenge owing to a lack of detailed microstructural characterization encompassing all length scales. Here, the hierarchical boron (B)‐induced microstructures in B‐doped Si80Ge20 alloys with different B concentrations are investigated to determine their precise effects on thermoelectric properties. By adopting a multi‐scale characterization approach, including X‐ray diffraction, scanning and transmission electron microscopy, and atom probe tomography, five distinctive B‐induced phases within Si80Ge20 alloys are identified. These phases exhibit different sizes, compositions, and crystal structures. Furthermore, their configuration is comprehensively determined according to B doping concentrations to elucidate their consequential impact on the unusual changes in carrier concentration, density‐of‐states effective mass, and lattice thermal conductivity. The study provides insights into the intricate relationship between hierarchical dopant‐induced microstructures and thermoelectric properties and highlights the importance of investigating all‐scale microstructures in excessively‐doped systems for determining the precise structure‐property relationships. [ABSTRACT FROM AUTHOR]

Herein, the influence of one‐ and two‐step preageing treatments prior to the artificial ageing step to peak age condition for three different 6xxx alloys, from low to high alloy content, is investigated. Analysis of the preaged conditions using atom probe tomography (APT) reveals a broad distribution of Mg and Si clusters, with some instances of Guinier‐Preston I zones present. Additionally, the high alloyed system exhibits a growth of precipitates toward a needle‐like shaped. These clusters formed during the preageing treatment serve as nucleation sites in the subsequent artificial ageing treatment, leading to an increase in hardness. Microstructural analysis conducted using transmission electron microscopy and APT demonstrates a reduction in the average precipitate length and a more narrow size distribution for T6 condition. This indicates that the preageing treatment results in a decreased portion of already overaged precipitates compared to the direct aged condition. Consequently, the more narrow size distribution of the precipitates leads to more effective hardening of the material, as a higher portion of precipitates is at or close to their optimum size. The investigations highlight the significant influence and positive effect of a preageing treatment at lower temperatures on the subsequent artificial ageing treatment. [ABSTRACT FROM AUTHOR]

Accessory minerals like zircon, rutile and monazite are routinely studied to inform about the timing and nature of geological processes. These studies are underpinned by our understanding of the transfer processes of trace elements and the assumption that the isotopic systems remain undisturbed. However, the presence of microstructures or Pb-bearing phases in minerals can lead to the alteration of the Pb isotopic composition. To gain insight into the relationship between Pb isotopic alterations from inclusions and microstructures, this study focused on inclusions from an ultra-high-temperature metamorphic rutile. The studied inclusions are submicrometer monazites, a common mineral rich in Pb but normally not present in rutile. The sample is sourced from Mt. Hardy, Napier Complex, East Antarctica, an ultra-high-temperature (UHT) metamorphic terrane. By applying correlative analytical techniques, including electron backscatter diffraction mapping, transmission electron microscopy (TEM), and atom probe tomography, it is shown that monazite inclusions are often in contact with low-angle boundaries and yield no preferred orientation. TEM analysis shows the monazite core has a mottled texture due to the presence of radiation damage and nanoclusters associated with the radiation damage defects that are rich in U, Pb, and Ca. Some monazites exhibit a core-rim structure. The rim yields clusters composed of Ca- and Li-phosphate that enclose Pb nanoclusters that are only present in small amounts compared to the core, with Pb likely diffused into the rutile-monazite interface. These textures are the result of two stages of Pb mobility. Initial Pb segregation was driven by volume diffusion during UHT metamorphism (2500 Ma). The second stage is a stress-induced recrystallization during exhumation, leading to recrystallization of the monazite rim and trace element transport. The isotopic signature of Pb trapped within the rutile-monazite interface constrains the timing of Pb mobility to ca. 550 Ma. [ABSTRACT FROM AUTHOR]

To detect hydrogen in materials at the atomic scale, atom probe tomography is now regularly used. In order to avoid cumbersome cryo‐preparation to suppress diffusion, often hydrogen is charged only into the finished specimen. Here, the use of hydrogen gas over electrochemical hydrogen has the advantage that the specimen is not contaminated with an electrolyte. So far, this "charging" has been done in large, expensive systems. Here, we introduce small devices that enable the exposure of atom probe specimens to hydrogen and potentially other gases, using only very small gas volumes. This enables the operation in regular laboratory environments without additional safety measures. These devices can be used to expose the specimen to hydrogen up to 10 bar/90°C. Higher temperatures may be attained with small changes. Validation of the success of charging with these setups is demonstrated through experiments employing deuterium charging of palladium atom probe tips. Research Highlights: Enabling the exposure of atom probe specimens to hydrogen and potentially other gases, using only very small gas volumes.Built setups can be assembled with little money and from freely available parts, making specimen charging much easier.Validation of the success of charging with these setups is demonstrated through experiments employing deuterium charging of palladium atom probe tips. [ABSTRACT FROM AUTHOR]

Mechanisms relating to growth and/or compositional modification of zircon occur at the atomic scale. For felsic igneous systems, processes responsible for growth patterns in zircon have previously remained elusive as the volume of material needed to analyze these compositional features using traditional in-situ methods is considerably larger than the typical sub-micron scale distribution of trace elements. To illuminate some of these driving forces, we characterize and quantify minor and trace element concentrations in igneous zircon grains by combining methods of cathodoluminescence (CL) imaging, electron microprobe microanalysis (EMPA) elemental maps for Hf, Y, Yb and U or Th, and atom probe tomography (APT). We focus on igneous zircon from the Chon Aike Silicic Large Igneous Province (Patagonia) that provide novel insights into (1) dissolution and re-crystallization during crustal anatexis, (2) crystallization to produce oscillatory zonation patterns that are typical of igneous zircons, and (3) the incorporation of trace element impurities (e.g., P, Be, and Al) at the nanoscale. Significantly, these APT volumes provide nanoscale sampling of boundaries between oscillatory growth zones in an igneous zircon to reveal compositional zoning of Y and, to a lesser extent P, which appear as high-angle, planar features. These concentration boundaries measured on the order of 10 to 12 nm are difficult to reconcile with proposed mechanisms for generating fine-scaled oscillations. Lastly, we fit diffusional profiles to measured Y concentrations to provide an estimate on the maximum timescales of zircon growth prior to eruption, as a function of the temperature at which diffusion occurred. When combined with known pressure-temperature-time paths for the magmatic system considered, these extremely short diffusion profiles that are resolvable by APT provide a powerful method to constrain timescales of crystal growth. [ABSTRACT FROM AUTHOR]

The reactor pressure vessel (RPV) is a critical barrier in nuclear power plants, but its embrittlement during service poses a significant safety challenge. This study investigated the effects of Cu-enriched clusters on the mechanical and magnetic properties of Fe-0.9 wt.%Cu model alloys through thermal aging. Using Vickers hardness tests, Magnetic Barkhausen Noise (MBN) detection, and Atom Probe Tomography (APT), the study aimed to establish a quantitative correlation between MBN signals, Vickers hardness, and Cu-enriched clusters, facilitating the non-destructive testing of RPV embrittlement. Experimental results showed that the hardness and MBN parameters (RMS and Vpp values) changed significantly with aging time. The hardness increased rapidly in the early stage (under-aged), followed by a plateau and then a decreasing trend (over-aged). In contrast, MBN parameters decreased initially and then increased. APT analysis revealed that Cu-enriched clusters increase in size to 4.60 nm and coalesced during aging, with their number density peaking to 3.76 × 1023 m−3 before declining. An inverse linear correlation was found between MBN signals and the combined factor Nd2Rg (product of the number density squared and the mean radius of Cu-enriched clusters). This correlation was consistent across both under-aged and over-aged states, suggesting that MBN signals can serve as applicable indicators for the non-destructive evaluation of RPV steel embrittlement. [ABSTRACT FROM AUTHOR]

Herein, the potential of using the thermomechanical treatment ausforming to optimize the microstructure of PH 13‐8 Mo maraging steels is investigated. Of particular interest are the effects on the formation of β‐NiAl precipitates and reverted austenite during subsequent aging. Ausforming experiments at deformation temperatures of 400 and 600 °C and strains of 40% and 70% are conducted using a deformation dilatometer. Afterward, the samples are subjected to aging at temperatures varying from 482 to 593 °C. This is followed by a thorough microstructural characterization ranging from light optical microscopy to X‐Ray diffraction and atom probe tomography. The results demonstrate that ausforming effectively refines the microstructure, resulting in a significant increase in hardness. Moreover, it is revealed that the ausforming parameters have a noticeable influence on the number density of β‐NiAl precipitates and the amount of reverted austenite. A well‐balanced microstructure containing relatively fine precipitates and a high amount of reverted austenite can be achieved by ausforming at 600 °C with 40% strain. Overall, the results prove a promising potential of ausforming for PH 13‐8 Mo maraging steels with regard to tailoring optimized microstructures, which could ultimately benefit the aerospace industry where these alloys are used. [ABSTRACT FROM AUTHOR]

The weld cladding on the inner surface of nuclear pressure vessels due to irradiation damage and thermal effect presents to a safety issue. Unfortunately, the effect of irradiation and long-term thermal treatment on the austenitic microstructure and austenitic hardening in austenitic stainless steel weld metals (ASSWMs) remains poorly understood. In this study, the effects of irradiation and thermal treatment on the austenitic microstructures and austenitic hardening of 308L ASSWMs were investigated using nanoindentation, atom probe tomography and transmission electron microscopy. The results suggested that irradiation resulted in the formation of Ni/Si-rich clusters, voids, and Frank loops in austenite, thereby inducing austenitic hardening. Subsequently, thermal treatment decreased the size and the number of Frank loops in irradiated austenite, which had a minor effect on austenitic hardening. However, thermal treatment promoted the growth of Ni/Si-rich clusters and void formation, which have a primary effect on austenitic hardening, thereby enhancing the hardening of irradiated austenite. Furthermore, thermal treatment has little effect on the microstructure and hardening of austenite. Then, irradiation promoted the formation of Ni/Si-rich clusters, voids, and Frank loops in thermally treated austenite, resulting in austenitic hardening. The interaction of irradiation and thermal treatment can promote the formation of voids. The austenitic hardening was mainly due to the contribution of Frank loops, voids, and Ni/Si-rich clusters, which acted as short-range barriers by pin-moving dislocations.

High strength combined with sufficient toughness is a fundamental prerequisite for steel in the field of lightweight construction. Joining high-strength steels by means of welding requires the use of highly advanced filler metals and a stress-relief post-weld heat treatment (PWHT) for optimum performance of the joint. However, such a heat treatment can lead to embrittlement in the weld metal. In this context, the present work deals with the influence of different PWHT holding temperatures on the microstructure and mechanical properties of a high-strength multipass all-weld metal to reveal the embrittlement phenomena. The all-weld metal was fabricated via gas metal arc welding using a metal cored wire with a minimum yield strength of 690 MPa. Charpy V-notch impact testing and tensile testing were carried out to characterize the strength and toughness of the all-weld metal in the as-welded condition and after a 2 h stress-relief PWHT at 520 °C, 580 °C, and 620 °C. The microstructure was characterized utilizing high-resolution techniques such as atom probe tomography and high-energy X-ray diffraction. The strength and toughness of the all-weld metal both decrease after PWHT with different holding temperatures. The cause for the observed embrittlement was found to be the formation of Mn-rich cementite precipitates. These carbides increase in size and phase fraction with increasing holding temperature and lead to a brittle transcrystalline cleavage fracture. Consequently, it was concluded that a gas metal arc welded joint with the investigated filler metal should not be exposed to stress-relief PWHT at temperatures higher than 580 °C.

Using atom probe tomography (APT), transmission electron microscopy (TEM), and hardness tests, the effect of Sn and Cu on the evolution of Mg:Si ratios in clusters and subsequent precipitation hardening behavior of pre-aged Al-1.0Mg-0.6Si alloys are investigated, and the underlying mechanism is revealed by density functional theory (DFT) calculation of interaction energy. It is shown that, the doping of Sn and/or Cu increases the average Mg:Si ratio in clusters. This increase is attributed to the strong interaction of Sn/Cu with Mg solutes, which enhances the binding of Mg to Si-rich clusters and results in a higher proportion of clusters with Mg:Si ratios near 1 (0.75–1.25). Consequently, the enhanced precipitation of β'' precipitates during artificial aging is observed in Sn and/or Cu doped alloys, due to the ease of clusters with Mg:Si ratios near 1 transform into β'' precipitates, leading to an improved hardening response. Notably, the combined doping of Sn and Cu exhibits the strongest aggregation tendency towards Mg solutes, yielding the most pronounced strengthening effects on precipitation and hardening response during artificial aging. Furthermore, a schematic model detailing the evolution of Mg:Si ratios in clusters is proposed, based on the APT results and DFT calculation of interaction energy.

Interactions at high temperatures between thin films and the Si substrate limit materials discovery using combinatorial processing platforms (CPPs). To overcome this, a diffusion and reaction barrier, SiO2, by thermal oxidation of Si tips is developed. The application of this diffusion barrier in CPPs for atomic‐scale investigations of new materials in atom probe tomography is reported. Thermal SiO2 layers (20 and 50 nm thick) are examined as barriers to separate coatings from Si tips. Pt is chosen as it easily forms silicides. CPPs are sequentially annealed in vacuum at 400 °C for 10 h, 600 °C for 2 h, and 800 °C for 2 h. The thermal SiO2 diffusion barrier remains stable and prevents intermixing at least up to 800 °C. Moreover, it provides improved film adhesion as dewetting of Pt on the oxide surface occurred at 800 °C instead of 600 °C without a thermal diffusion barrier. A comprehensive structural and chemical analysis of the Pt film, the thermal SiO2 layer, and their interfaces is performed using scanning and transmission electron microscopy, and atom probe tomography. As a result, the thermal SiO2 forms a stable barrier, even at the lowest thickness of 20 nm, avoiding the formation of Pt silicides, even at 800 °C. [ABSTRACT FROM AUTHOR]

In microalloyed steels, interphase precipitation involves the formation of precipitates at the ferrite/austenite interface during their transformation. The study on interphase precipitation has been ongoing since the 1970s and remains highly relevant today. While this metallurgical approach has been applied in various products of advanced steels, its application to cold‐rolled steels is still absent. This study presents a development of cold‐rolled dual‐phase (DP) steels strengthened by interphase‐precipitated carbides. A CALPHAD‐based approach is established to facilitate austenite to ferrite transformation coupled with interphase precipitation during simulated annealing for cold‐rolled DP steels. Further experimental investigations on the effects of V and Mo optimize the alloy composition, and the corresponding nano/microstructures are validated by transmission electron microscopy (TEM) and atom probe tomography. Besides, this work further addresses the impacts of interfacial segregation and microsegregation bands on the capability of interphase precipitation in the studied steels. In summary, this work charts a new pathway for the development of cold‐rolled DP steels strengthened by interphase‐precipitated carbides, advancing the realm of high‐strength steels. [ABSTRACT FROM AUTHOR]

To achieve the desired microstructural properties, the ongoing development and innovation in new structural steels require novel thermal processing. This study aims to improve the mechanical properties of a commercial spring carbon–silicon steel by tailoring its microstructure through a process involving quenching and partitioning (Q&P) followed by bainitic transformation. A two‐stage Q&P process is proposed to generate a nanoscale dispersion of stable retained austenite and carbides within the tempered martensite and bainite microstructure. The resulting tensile properties demonstrate a yield strength of 1280 MPa, an ultimate tensile strength of 1875 MPa, and a total elongation of 8.03%. These values surpass those of conventional spring 9254 steel, highlighting the effectiveness of the thermal treatment design. Microstructure analysis reveals the presence of tempered martensite, bainite sheaves, nanoscale carbides, and aggregates of retained austenite. Moreover, the resulting body‐centered cubic matrix exhibits minimal lattice tetragonality of ≈1.0051, coupled with stable retained austenite featuring a carbon concentration of ≈3.42 ± 0.5 wt%, resulting in outstanding strength–ductility properties. These findings indicate that the proposed two‐stage Q&P process, followed by bainitic transformation, significantly enhances the mechanical properties of carbon–silicon steels, making it a promising candidate for high‐performance spring applications. [ABSTRACT FROM AUTHOR]

At temperatures above about 600 °C, alkali feldspar forms a continuous solid solution between the Na and K end members. Towards lower temperatures a miscibility gap opens, and alkali feldspar of intermediate composition exsolves, forming an intergrowth of relatively more Na-rich and K-rich lamellae. During exsolution, the crystal structure usually remains coherent across the lamellar interfaces, a feature that may be preserved over geological times. Due to the compositional dependence of the lattice parameters, coherent intergrowth requires that the lamellae are elastically strained. The associated elastic strain energy counteracts exsolution, and the solvus delimiting the misciblity gap for coherent intergrowth lies below the solvus for strain free phase equilibria. To determine the coherent solvus, homogeneous gem quality alkali feldspar of intermediate composition was annealed at conditions falling into the two-phase region of the phase diagram. Thereby a coherent intergrowth of approximately 10–20 nanometers wide lamellae was produced. Lamellar compositions were determined with atom probe tomography defining points on the coherent solvus. In parallel, the coherent solvus was calculated using a thermodynamic mixing model calibrated on the same alkali feldspar as used for the exsolution experiments and accounting for the elastic strain energy associated with coherent lamellar intergrwoth. The experimentally determined and the calculated coherent solvus are in excellent agreement indicating that phase equilibria in coherent lamellar intergrowth of alkali feldspar are adequately described, providing a sound basis for the interpretation of phase relations in coherently exsolved alkali feldspar. [ABSTRACT FROM AUTHOR]

This study demonstrates the successful fabrication of a multi-material 18Ni(300) maraging steel – CoCrMo alloy using laser powder bed fusion (L-PBF), which in its as-built state, displays suboptimal mechanical performance. Addressing this, we propose different heat treatments that mutually enhance the properties of both alloys. Comparative analysis of texture development, precipitation sequence and mechanical properties of the dual structures at different scales has been conducted. The results indicate the cooperative strengthening of intragranular γ–ϵ transformation in CoCrMo, and Ni3Ti precipitation in maraging steel. Adding the solution treatment also balanced the formation of acicular Ni3Ti clusters with (Fe, Ni, Co)2(Ti, Mo) precipitates, and revealed that chemical segregation influences austenite reversion. Initial evidence of local grain variant selection has been revealed in as-built samples due to thermal cycling and austenite reversion, which generates residual stresses, recoil forces and convective flow. Surprisingly, the missing variants can also be inherited after heat treatment with insufficient solution temperatures.

Metal matrix alloying is an effective modification strategy to introducing an interfacial carbide at the Cu/diamond interface for improving thermal conductivity of Cu/diamond composite. However, the distribution and diffusion of C and alloying elements in Cu/diamond composite are still unclear. Here, transmission electron microscopy was utilized to characterize the microstructure of Cu/diamond interface and an atom probe tomography nanotip of the Cu–B/diamond composite was successfully prepared. For the first time, we give a clear distribution of C and alloying elements in a Cu–B/diamond composite. The formation of B 4 C is the consequence of C and B atoms diffusing to the Cu/diamond interface. The solubility of B in Cu is confirmed to be 0.06 at.% at room temperature. The extremely low solubility (<4.8 ppm) of C in Cu limits the reaction between C and B, and thus a B-rich and C-free area is formed between Cu and B 4 C. The residual C and B atoms are accumulated at the Cu boundaries, forming carbides after the Cu matrix solidifies. The presence of solid-solution atoms and carbides at the Cu boundaries decreases the thermal conductivity of the Cu matrix and further the Cu–B/diamond composite. The findings provide insights into the formation of interfacial carbide and the regulation of thermal conductivity in Cu/diamond composite modified by metal matrix alloying methods. [ABSTRACT FROM AUTHOR]

Garnet is a common rock‐forming mineral that occurs in a variety of rock types and over a wide range of pressure (P)–temperature (T) conditions in the Earth's lithosphere. Because garnet is considered a high‐strength mineral stable across an extensive range of conditions (1–25 GPa, <300–2000°C), it is generally accepted that garnets can retain their microstructures and chemical composition during deformation and metamorphism. Therefore, garnet is commonly used as a geothermobarometer and geochronometer to provide P–T and timing constraints on tectonic events. Herein, we study garnet from an eclogite facies mylonite (central Australia) to investigate the mechanisms of element mobility during high‐strain deformation under relatively dry, lower crustal conditions. Electron backscatter diffraction (EBSD) and electron channelling contrast imaging (ECCI) reveal evidence of crystal plasticity associated with brittle deformation in the form of heterogeneous misorientation patterns and low‐angle grain boundaries developed over length scales of 20–50 μm in the rims of garnet porphyroclasts. Atom probe tomography (APT) analysis of a low‐angle grain boundary within a highly strained portion of a clast shows Ca enrichment and Mg depletion along dislocations, whereas APT data along the rim of a mostly undeformed clast reveal a homogeneous distribution of garnet major components in the specimen matrix with the exception of Ca, Fe and Mg enrichment within a healed microfracture. The above‐mentioned results suggest that under relatively dry conditions, crystal plasticity enhances bulk element mobility via pipe diffusion, highlighting the importance of deformation‐induced microstructures on element mobility, with important implications for the robust and reliable use of garnet as a petrological tool. [ABSTRACT FROM AUTHOR]

The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0–10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and Mn levels. Sn enrichment at the free surface was insensitive to the Mn alloy concentration, which was partially attributed to the opposing effects of Mn on segregation thermodynamics and kinetics: Mn increases the driving force for Sn segregation via reducing Sn solubility in Fe but also reduces the effective Sn diffusivity by increasing the austenite volume fraction. This insensitivity was exacerbated by the depletion of solute Mn near the surface due to the selective oxidation of Mn. Thus, Sn segregation occurred in regions with a local Mn concentration lower than the nominal bulk composition of the alloys suggested. Sn enrichment at the metal/external oxide interface was reduced compared to the free surface and decreased with increasing bulk Mn content, which was attributed to changes in the external oxide morphology and metal/internal oxide interfaces acting as Sn sinks. [ABSTRACT FROM AUTHOR]

We investigate the microscopic behaviour of hydrogen‐containing species formed on the surface of III‐N semiconductor samples by the residual hydrogen in the analysis chamber in laser‐assisted atom probe tomography (APT). We analysed AlGaN/GaN heterostructures containing alternate layers with a thickness of about 20 nm. The formation of H‐containing species occurs at field strengths between 22 and 26 V/nm and is independent of the analysed samples. The 3D APT reconstruction makes it possible to map the evolution of the surface behaviour of these species issued by chemical reactions. The results highlight the strong dependence of the relative abundances of hydrides on the surface field during evaporation. The relative abundances of the hydrides decrease when the surface field increases due to the evolution of the tip shape or the different evaporation behaviour of the different layers. [ABSTRACT FROM AUTHOR]

The behavior of catalytic particles depends on their chemical structure and morphology. To reveal this information, the characterization with atom probe tomography has huge potential. Despite progresses and papers proposing various approaches towards the incorporation of particles inside atom probe tips, no single approach has been broadly applicable to date. In this paper, we introduce a workflow that allowed us to prepare atom probe specimens from Ga particles in suspension in the size range of 50 nm up to 2 μm. By combining dielectrophoresis and electrodeposition in a suitable way, we achieve a near‐tip shape geometry, without a time‐consuming FIB lift‐out. This workflow is a simple and quick method to prepare atom probe tips and allows for a high preparation throughput. Also, not using a lift‐out allowed us to use a cryo‐stage, avoiding melting of the Ga particles, while ensuring a mechanical stable atom probe tip. The specimen prepared by this workflow enable a stable measurement and low fracture rates. Research Highlights: Enabling cryo‐preparation of (nano)particles for the atom probe.Characterization of surface and bulk elemental distribution of GaPt model SCALMS. [ABSTRACT FROM AUTHOR]

Ion irradiation combined with nanoindentation is a promising tool for studying irradiation-induced hardening of nuclear materials, including reactor pressure vessel (RPV) steels. For RPV steels, the major sources of hardening are nm-sized irradiation-induced dislocation loops and solute atom clusters, both representing barriers for dislocation glide. The dispersed barrier hardening (DBH) model provides a link between the irradiation-induced nanofeatures and hardening. However, a number of details of the DBH model still require consideration. These include the role of the unirradiated microstructure, the proper treatment of the indentation size effect (ISE), and the appropriate superposition rule of individual hardening contributions. In the present study, two well-characterized RPV steels, each ion-irradiated up to two different levels of displacement damage, were investigated. Dislocation loops and solute atom clusters were characterized by transmission electron microscopy and atom probe tomography, respectively. Nanoindentation with a Berkovich indenter was used to measure indentation hardness as a function of the contact depth. In the present paper, the measured hardening profiles are compared with predictions based on different DBH models. Conclusions about the appropriate superposition rule and the consideration of the ISE (in terms of geometrically necessary dislocations) are drawn. [ABSTRACT FROM AUTHOR]

High‐strength steels are susceptible to H‐induced failure, which is typically caused by the presence of diffusible H in the microstructure. The diffusivity of H in austenitic steels with face‐centered cubic (fcc) crystal structure is slow. The austenitic steels are hence preferred for applications in the hydrogen‐containing atmospheres. However, the fcc structure of austenitic steels is often stabilized by the addition of Ni, Mn, or N, which are relatively expensive alloying elements to use. Austenite can kinetically also be stabilized using C. Herein, an approach is applied to a commercial cold work tool steel, where C is used to fully stabilize the fcc phase. This results in a microstructure consisting of only austenite and M7C3 carbide. An exposure to H by cathodic hydrogen charging exhibits no significant influence on the strength and ductility of the C‐stabilized austenitic steel. While this material is only a prototype based on an existing alloy of different purposes, it shows the potential for low‐cost H‐resistant steels based on C‐stabilized austenite. [ABSTRACT FROM AUTHOR]

Through its capability for 3D mapping of Li at the nanoscale, atom probe tomography (APT) is poised to play a key role in understanding the microstructural degradation of lithium‐ion batteries (LIB) during successive charge‐ and discharge cycles. However, APT application to materials for LIB is plagued by the field induced delithiation (deintercalation) of Li‐ions during the analysis itself that prevents the precise assessment of the Li distribution. Here, we showcase how a thin Cr‐coating, in‐situ formed on APT specimens of NMC811 in the focused‐ion beam (FIB), preserves the sample's integrity and circumvent this deleterious delithiation. Cr‐coated specimens demonstrated remarkable improvements in data quality and virtually eliminated premature specimen failures, allowing for more precise measurements via. improved statistics. Through improved data analysis, we reveal substantial cation fluctuations in commercial grade NMC811, including complete grains of LiMnO. The current methodology stands out for its simplicity and cost‐effectiveness and is a viable approach to prepare battery cathodes and anodes for systematic APT studies. [ABSTRACT FROM AUTHOR]

β-titanium (β-Ti) alloys are useful in diverse industries because their mechanical properties can be tuned by transforming the metastable β phase into other metastable and stable phases. Relationships between lattice parameter and β-Ti alloy concentrations have been explored, but the lattice parameter evolution during β-phase transformations is not well understood. In this work, the β-Ti alloys, Ti-11Cr, Ti-11Cr-0.85Fe, Ti-11Cr-5.3Al, and Ti-11Cr-0.85Fe-5.3Al (all in at.%), underwent a 400 °C aging treatment for up to 12 h to induce the β-to-ω and β-to-α phase transformations. Phase identification and lattice parameters were measured in situ using high-temperature X-ray diffraction. Phase compositions were measured ex situ using atom probe tomography. During the phase transformations, Cr and Fe diffused from the ω and α phases into the β matrix, and the β-phase lattice parameter exhibited a corresponding decrease. The decrease in β-phase lattice parameter affected the α- and ω-phase lattice parameters. The α phase in the Fe-free alloys exhibited α-phase c/a ratios close to those of pure Ti. A larger β-phase composition change in Ti-11Cr resulted in larger ω-phase lattice parameter changes than that for Ti-11Cr-0.85Fe. This work illuminates the complex relationship between diffusion, composition, and structure for these diffusive/displacive transformations. [ABSTRACT FROM AUTHOR]

Abstract Interactions at high temperatures between thin films and the Si substrate limit materials discovery using combinatorial processing platforms (CPPs). To overcome this, a diffusion and reaction barrier, SiO2, by thermal oxidation of Si tips is developed. The application of this diffusion barrier in CPPs for atomic‐scale investigations of new materials in atom probe tomography is reported. Thermal SiO2 layers (20 and 50 nm thick) are examined as barriers to separate coatings from Si tips. Pt is chosen as it easily forms silicides. CPPs are sequentially annealed in vacuum at 400 °C for 10 h, 600 °C for 2 h, and 800 °C for 2 h. The thermal SiO2 diffusion barrier remains stable and prevents intermixing at least up to 800 °C. Moreover, it provides improved film adhesion as dewetting of Pt on the oxide surface occurred at 800 °C instead of 600 °C without a thermal diffusion barrier. A comprehensive structural and chemical analysis of the Pt film, the thermal SiO2 layer, and their interfaces is performed using scanning and transmission electron microscopy, and atom probe tomography. As a result, the thermal SiO2 forms a stable barrier, even at the lowest thickness of 20 nm, avoiding the formation of Pt silicides, even at 800 °C.

Fe-Cr alloys serve as model alloys for the investigation of radiation induced effects in ferritic-martensitic steels which are candidate structural materials for future fusion reactors. In this work the effect of Cr segregation and/or agglomeration in 490 keV Fe+ ion irradiated Fe-10at%Cr alloys in the form of thin films is investigated. The irradiations took place at 300 °C at doses ranging from 0.5 to 20 displacements per atom (dpa). Polarized Neutron Reflectivity (PNR) measurements were used for the determination of the solute Cr concentration in the Fe-Cr matrix. Cr depletion from the Fe-Cr matrix up to 2.4 at% was found. This is related to solute Cr decrement as the accumulated dose increases. After the damage of 4 dpa, solute Cr reaches the asymptotic value of 8.4 at%, close to that of the thermodynamic equilibrium in Fe-Cr. Atom Probe Tomography (APT) measurements showed that after irradiation Cr accumulates into clusters the majority of which is co-located with oxygen.

In reactor pressure vessel materials, the formation of Mn- and Ni-rich nanoclusters is a major cause of neutron irradiation embrittlement. The segregation of these solute atoms into dislocation loops has attracted attention as a mechanism to accelerate solute clustering. In this study, the behaviors of solute Mn and Ni atoms in Fe-0.6wt.%Ni, Fe-1.4wt.%Mn, and Fe-1.4wt.%Mn-0.6wt.%Ni alloys irradiated at 400 °C up to 3 dpa were analyzed using three-dimensional atom probe tomography. Solute atom clusters were observed in all materials, and their shapes were spherical, flat, and torus in FeNi, FeMn, and FeMnNi, respectively. In ternary alloy FeMnNi, Mn and Ni atoms were concentrated in the sample in the form of arcs, and the orientation of the plane containing the arcs was estimated by comparing field desorption images. The size, number density, and orientation of this structure were found to be in good agreement with those of both types of dislocation loops, namely, b = 1/2 〈111〉 and b = 〈100〉, identified in a previous study using the same material. The positions of Ni and Mn enrichment did not fully overlap. Ni atoms tended to be concentrated more in the inner part of the loop than the Mn atoms. Mn atoms were enriched only in the vicinity of the dislocation loops, whereas Ni atoms showed a higher concentration inside the dislocation loops than in the bulk.

Oxide dispersion strengthened steels are key alloys used in nuclear installations. Steels with chromium content of up to 10 wt % are suitable due to their advantageous properties and these alloys are used for the construction of technological devices in the primary circuit of nuclear power plants. From other studies, it can be concluded that chromium has anti-corrosive properties due to the formation of a passivation layer, which results in reduced activation of the material by thermal neutrons. Macroscopic properties are determined by their microstructure, and therefore, the description of the microstructure is important. Transmission Mössbauer spectroscopy and atom probe tomography were used to characterise the material. This provides information about the physical and/or chemical environment of the resonant atoms can be obtained. Obtained spectral parameters reach saturation values from which the solubility limit of chromium in iron can be determined. In Cr-rich phase, the solubility limit can be estimated from the value of spectral parameters of the single-line in the spectrum annealed for the longest time. The suggested procedures are subsequently applied to the case studies of stainless steels suitable for the construction of various components of the III+/IVth generation of nuclear reactors (including fast and fusion reactors).

Co-precipitation of γ′ and γ′′ is the main strengthening mechanism that provides superior high-temperature strength in directly aged Alloy 718 aerospace parts. Control of their morphology, fraction, and configuration might allow exposure to more demanding operation environments in next-generation aircraft engines. The density of geometrically necessary dislocations introduced during hot deformation has been shown to significantly affect the co-precipitate morphology of γ′ and γ′′ in materials free of the δ-phase. However, the combined effects of geometrically necessary dislocation density and lower Nb content due to higher δ-phase fractions on co-precipitation behaviour and strengthening remain unknown. We verify these effects by hardness testing as a proxy for high-temperature strength in materials with 4.1 % δ-phase fraction. Deformation at 950 °C yields a remarkable increase of 12 % in hardness after direct ageing, explained by the prevalence of complex co-precipitate configurations. Deformation at 1000 °C decreases the δ-phase fraction and geometrically necessary dislocation density but achieves up to 19 % volume fractions of γ″, leading to a predominance of monoliths and duplet co-precipitates and a better direct ageing response. Atom probe microscopy reveals the flux of elements during co-precipitation. We recommend a δ-annealing treatment before the final forging step for manufacturing stronger Alloy 718 aerospace parts.

The precipitation of grain boundary (GB) κ-carbides critically influences the damage-tolerance ability of high-Mn high-Al lightweight steels, particularly in harsh environments (cryogenic and H environments). The formation and growth behavior of these carbides thus need to be understood. In this work, we use atom probe tomography and four-dimensional scanning transmission electron microscopy to study the formation mechanisms of GB κ-carbides in a Fe-28Mn-8Al-1.3C (wt.%) steel that is aged at 550°C, a temperature at which GB κ-carbide formation is often believed to be delayed or avoided. We observe that the formation of GB κ-carbides results from spinodal decomposition of grain interior (GI) κ-carbides and their further interaction with GB planes rather than from heterogeneous GB nucleation, as has been formerly proposed. However, the subsequent growth of GB κ-carbides shows different kinetics in comparison to GI κ-carbides. The underlying reason and its implications for future microstructure design of such steels are discussed.

The effect of cobalt on the precipitation hardening behavior of the maraging stainless steels was studied. The hardness test indicated that cobalt addition could advance peak aging time and generate a higher peak hardness. The statistical results of nano-size precipitates distribution demonstrated that cobalt increased the density of precipitates, thus resulting in a stronger precipitation hardening contribution. Based on the first-principles calculations and atom probe tomography (APT) results, a possible mechanism has been proposed to reveal the underlying mechanism: cobalt promotes the nucleation of precipitates by decreasing the diffusion activation energy of Ni and Ti.

Titanium alloys have been gaining importance in various industries due to their advantageous combination of strength, low density, excellent corrosion/oxidation resistance, and superior mechanical properties at elevated temperatures. Recently, eutectoid Ti–Cu alloys have been explored as promising candidates for advanced processes. This work investigates the effects of Fe and Al on a Ti-5.9Cu alloy using multi-scale characterization techniques. While Fe acts as a β-stabilizing element (despite being a sluggish eutectoid former), Al acts as an α-stabilizer. This work focuses on the effects of combined addition of these elements, studied in different heat treatment conditions. The results show that a fine, equiaxed microstructure is obtained in the binary Ti-5.9Cu alloy, whereas the addition of 2 wt% Fe, or 2 wt% Fe combined with 2 wt% Al to the Ti-5.9Cu alloy deteriorates the effect of grain refinement and coarse, columnar grains result and a small amount of β-phase is retained. Further, the microstructure resulting from the eutectoid decomposition is altered dramatically from a lamellar pearlitic in the binary alloy to a lath-like α-phase with diverse decomposition products in the ternary and quaternary alloys accompanied by increasing hardness values. Evaluation of the α misorientation suggests that a substantial amount of non-Burgers α is present in the Ti-Cu alloy in contrast to the results of the ternary and quaternary alloys. The observed Cu-rich intermetallic compound was identified as Ti2Cu phase with off-stoichiometric composition. Results obtained explain how adding either Fe or Fe and Al leads to substantial hardening.

The reactor pressure vessel (RPV) is a critical barrier in nuclear power plants, but its embrittlement during service poses a significant safety challenge. This study investigated the effects of Cu-enriched clusters on the mechanical and magnetic properties of Fe-0.9 wt.%Cu model alloys through thermal aging. Using Vickers hardness tests, Magnetic Barkhausen Noise (MBN) detection, and Atom Probe Tomography (APT), the study aimed to establish a quantitative correlation between MBN signals, Vickers hardness, and Cu-enriched clusters, facilitating the non-destructive testing of RPV embrittlement. Experimental results showed that the hardness and MBN parameters (RMS and Vpp values) changed significantly with aging time. The hardness increased rapidly in the early stage (under-aged), followed by a plateau and then a decreasing trend (over-aged). In contrast, MBN parameters decreased initially and then increased. APT analysis revealed that Cu-enriched clusters increase in size to 4.60 nm and coalesced during aging, with their number density peaking to 3.76 × 1023 m−3 before declining. An inverse linear correlation was found between MBN signals and the combined factor Nd2Rg (product of the number density squared and the mean radius of Cu-enriched clusters). This correlation was consistent across both under-aged and over-aged states, suggesting that MBN signals can serve as applicable indicators for the non-destructive evaluation of RPV steel embrittlement.

Understanding the early stages of interactions between oxygen and material surfaces—especially at very high spatial resolutions—is highly beneficial for fields ranging from materials degradation, corrosion, geological sciences, forensics, and catalysis. The ability of in situ atom probe tomography (APT) is demonstrated to track the diffusion of oxygen and metal ions at nanoscale spatial resolution during the early stages of oxidation of a model Fe–Cr–Ni alloy. Using 18O isotope tracers in these in situ APT experiments and complementary ex situ multimodal microscopy, spectroscopy, and computational simulations allows to precisely analyze the kinetics of oxidation and determine that outward cation diffusion to oxide/air interface is the primary mechanism for intragranular oxide growth in this alloy at 300 °C. This unique in situ isotopic tracer APT approach and the insights gained can be highly beneficial for studying early stages of gas–surface reactions in a broad array of materials.

In this work, the nanostructure of oxide dispersion-strengthened steels was studied by small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and atom probe tomography (APT). The steels under study have different alloying systems differing in their contents of Cr, V, Ti, Al, and Zr. The methods of local analysis of TEM and APT revealed a significant number of nanosized oxide particles and clusters. Their sizes, number densities, and compositions were determined. A calculation of hardness from SANS data collected without an external magnetic field, or under a 1.1 T field, showed good agreement with the microhardness of the materials. The importance of taking into account two types of inclusions (oxides and clusters) and both nuclear and magnetic scattering was shown by the analysis of the scattering data. [ABSTRACT FROM AUTHOR]

This work aims at understanding the formation of a beneficial thin continuous aluminum (Al)-rich interfacial layer with uniform distribution of fine equiaxed Fe-Al crystals formed at the substrate/coating interface during the initial stages of interfacial reactions as well as hindrance of Fe dissolution in Zn layer as soon as copper (Cu) pre-coated high-strength steel substrate is immersed into the molten zinc (Zn) bath containing 0.2 wt.% Al. Pre-coated Cu does not allow the immediate interaction and interdiffusion of Fe and Zn because of the positive heat of mixing between Fe and Cu. As the Cu dissolves in liquid Zn, counter-diffusion of Al and Zn toward the steel interface allows Fe to react with Al and Zn forming the thin Fe-Al inhibition layer with finer equiaxed grains. Moreover, dissolved Cu in the Zn layer would also prevent Fe diffusion in Zn in the time span during dipping, which is beneficial. Atom probe tomography (APT) analysis at the substrate/coating interface location reveals the presence of 56.22 ± 1.36 at.% Al, 35.01 ± 1.31 at.% Fe, 6.33 ± 0.66 at.% Zn, and 0.032 ± 0.01 at.% Cu, similar to the intermetallic compound of Fe2Al(5-x)Znx, as well Cu in the Zn layer supporting the above reasoning. [ABSTRACT FROM AUTHOR]

The mineral zircon is used widely to constrain the age of rocks and the processes that formed them. Although zircon is robust to a range of physical and chemical processes, it may show evidence for rapid re-equilibration that is generally considered to reflect interaction with hydrous fluids. Here, we show that zircon grains that crystallized from melt produced during the catastrophic meltdown of the Chernobyl nuclear reactor exhibit re-equilibration textures that occurred in an environment without free water. The process of re-equilibration involved a melt-mediated interface-coupled dissolutionreprecipitation that took place over a few days to produce textures that are commonly observed in igneous and anatectic systems. Thus, the composition of zircon can be modified even in the absence of hydrous fluids in a short time frame. Through this process, zircon crystals may track the timing of the last silicate melt they interacted with. [ABSTRACT FROM AUTHOR]

The precipitation of grain boundary (GB) κ-carbides critically influences the damage-tolerance ability of high-Mn high-Al lightweight steels, particularly in harsh environments (cryogenic and H environments). The formation and growth behavior of these carbides thus need to be understood. In this work, we use atom probe tomography and four-dimensional scanning transmission electron microscopy to study the formation mechanisms of GB κ-carbides in a Fe-28Mn-8Al-1.3C (wt.%) steel that is aged at 550°C, a temperature at which GB κ-carbide formation is often believed to be delayed or avoided. We observe that the formation of GB κ-carbides results from spinodal decomposition of grain interior (GI) κ-carbides and their further interaction with GB planes rather than from heterogeneous GB nucleation, as has been formerly proposed. However, the subsequent growth of GB κ-carbides shows different kinetics in comparison to GI κ-carbides. The underlying reason and its implications for future microstructure design of such steels are discussed. We originally report that grain boundary κ-carbides can result from spinodal decomposition rather than conventional heterogeneous nucleation and refute the possibility of avoiding their precipitation by controlling aging parameters. [ABSTRACT FROM AUTHOR]

In this work, hardness and micro- and nano-structure of W–10Cr–0.5Y alloy, which is a promising material for fusion reactors, before and after irradiation with Fe ions with an energy of 5.6 MeV at 500°C were studied. Nanoindentation for hardness measurement and transmission electron microscopy and atom probe tomography for structural changes were used. A formation of Cr clusters with the concentration of Cr in clusters of 52 ± 2 and 77 ± 3 at % for radiation doses of 1 and 10 displacement per atom (dpa), respectively, was detected. An increase in the hardness with increasing the irradiation dose from 1 to 10 dpa was found, which correlates with the increase in the Cr concentration in clusters. [ABSTRACT FROM AUTHOR]

Solid solution strengthening is a well‐known strengthening mechanism for Al (Mg, Si) alloys. The distribution of solute atoms plays an important role in the enhancement of the mechanical properties. As‐quenched, dilute, Al alloys are analysed by atom probe tomography (APT) and mechanical testing (microhardness, tensile testing) and these data have been employed in order to assess the 3D distribution of solute atoms in the solid solutions. An innovative approach is to abstain from the conventional logic of binary versus ternary alloys in data analysis in favor of a less‐concentrated versus more‐concentrated strategy. This approach enables for the first time that the integration of first‐principles Condon–Morse atomic interaction effects, APT, and mechanical testing, and first principles effects (field, proximity, chemical, and atomic size), which results in a novel empirical singleton‐cluster plot. The plot allows differentiation between singletons, solute clusters, and coclusters as well as between the less‐concentrated and more‐concentrated alloys. The plot also allows determination of the maximal yield strengths from cluster strengthening and from singletons in the absence of clustering. Most critically, this new approach in data analysis allows for the first time the determination of the dmax (maximal distance between solutes in a cluster) based on experimental results. [ABSTRACT FROM AUTHOR]

The mechanical property and microstructures of the 15-5PH stainless steel aged at 500 °C for different times have been studied in detail by using transmission electron microscopy and atom probe tomography. The precipitation-hardening effect is significant during aging and the peak hardness occurs at 2 h, but prolonged aging decreases the hardness significantly. The peak hardness is attributed to the formation of a large number of Cu-rich precipitates of 3-6 nm in diameter, with the Ni and Mn atoms segregating around the Cu-rich precipitates and forming a core–shell structure. The over-aging process increases the size of Cu-rich precipitates and causes Si and Nb atoms to segregate to the vicinity of Ni and Mn atoms, forming Nb-rich and NbN-rich particles. The formation of various phase precipitates, including possible G-phase particles, and their effects on mechanical property are discussed. [ABSTRACT FROM AUTHOR]

Micrometeorites (MMs) recovered from the Earth's surface may have undergone significant changes prior to their collection, including weathering while residing in the terrestrial environment. These alteration processes, such as the precipitation of hydrous phases, may overprint both primary and atmospheric entry features, obscuring pre-existing material properties. In addition, weathering exerts a prominent control on the geochemical interactions, such as species mobility, between extraterrestrial material and the terrestrial environment, particularly in Antarctica. In this study, we have characterised the textural and compositional consequences of weathering on an unmelted, fine-grained, Antarctic MM, which includes the mapping of nanometre-scale features using atom probe tomography. In particular, we investigate geochemical behaviour across textural boundaries in the MM and observe nanoscale elemental heterogeneity within complex alteration assemblages. In one sample region, a compositional boundary is highlighted by distinct elemental differences, consistent with a weathering encrustation of mixed mineralogies, while analyses in other targeted regions show evidence for nanoscale elemental networks, as well as a grain boundary adjacent to a carbon-rich region. We discuss our findings in the context of terrestrial weathering as a dominant cause for the nanoscale features observed. Weathering processes responsible for these features include the leaching of extraterrestrial material, precipitation of secondary alteration products with associated layering, and the influence of mechanical stress on pre-existing weaknesses. From these results, we derive a weathering sequence to explain the formation of the alteration product assemblage and highlight the controls on MM geochemistry in the terrestrial environment. Our observations show that nanoscale carbonaceous material may be preserved in oxy-hydroxides under icy conditions, which can also act as tracers for local environmental changes. [ABSTRACT FROM AUTHOR]

The metallurgy, mechanical properties, and corrosion of Cu, proposed as the corrosion barrier for Canadian used fuel containers (UFCs) for use in a deep geological repository (DGR), have been studied for decades. Bulk properties have been reported, and the knowledge applied to strengthen the performance of Cu produced by electrodeposition and cold spray. Despite this success, many degradation mechanisms are unclear from bulk testing, which cannot capture nanoscale phenomena driving degradation. This study provides examples using state‐of‐the‐art microscopy to understand mechanisms of Cu degradation, specifically for UFCs. Subtle changes in the electrodeposited Cu microstructure due to oxygen segregation are observed using atom probe tomography (APT). In aggressive sulfide‐containing environments, corrosion of the cold‐sprayed Cu occurs along particle–particle interfaces, likely inherent to the manufacturing process. Microscale tensile testing at particle–particle interfaces confirms brittle cracking in the cold‐sprayed Cu. Although experiments are not consistent with DGR conditions, results do warrant further study on the performance of the cold‐sprayed Cu in particular. [ABSTRACT FROM AUTHOR]