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Chemical analysis of shape memory alloys (SMAs) is critically important to characterization due to the high compositional sensitivity of shape memory properties. Chemical analytical techniques must be carefully planned and implemented as they may alter the sample or skew the analysis. Characterization with a complex technique, such as atom probe tomography (APT) used for a nontrivial material like NiTiHf SMAs, is uniquely challenging when determining accuracy of 3D compositional data. APT is a high-resolution alternative for measuring nano-scale compositions and only a few studies have used this technique to examine the 3D nanoscale features of H-phase precipitates within NiTiHf systems. In this study, a Ni 50.5 Ti 34.5 Hf 15 SMA was aged to characterize the H-phase nanoprecipitates and to discuss the influence of aging temperature to promote Ni-enriched H-phase, which is much greater than previously determined within Ni-rich compositions. [Display omitted] [ABSTRACT FROM AUTHOR]

Grain boundary segregation of solute elements is known to be strongly influenced by boundary characters. In this study, the equilibrium segregation of phosphorus at ferrite grain boundaries was quantitatively evaluated using three-dimensional atom probe after annealing a high-purity iron-phosphorus binary alloy with a low phosphorus content of 0.011 mass% at 873 K for 86.4 ks. The results of multiple grain boundaries with various characters, as analyzed using electron backscatter diffraction combined with characterization of the grain boundary plane orientation, reveal that the amount of phosphorus segregation increases with the increment in boundary misorientation angle, with especially large scatter existing in the case of high-angle grain boundaries. Further analysis via the decomposition of boundary misorientation into the contributions of tilt and twist angles indicates that the enlargement in tilt component has a relatively larger promoting effect on phosphorus segregation than the twist counterpart. [Display omitted] [ABSTRACT FROM AUTHOR]

Creep deformation at intermediate temperatures and high-stress conditions in a second-generation Ni-based superalloys occurs by continuous shearing of γ and γ' phases that lead to the formation of a high number density of stacking faults (SFs). Solute segregations to these faults highlight that their diffusivities play a critical role as creep rate limiting solutes. Although most of the earlier works focus on solute segregations to SFs inside γ', in this work, we show evidence of Re and W segregation at the SFs in the γ matrix phase by atomic-scale analysis using atom probe tomography. Based on the observations, we derive possible solute diffusion mechanisms along the SFs that contribute to a new understanding of creep deformation and their dependence on the specific solutes, especially Re and W in the alloy. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydrogen (H) embrittlement in high-strength steels can be mitigated by introducing H traps into the microstructure. The co-precipitation model steel in this work contains intermetallic ß-NiAl and secondary Cr-carbides, which provide abundant trapping sites. Needle-shaped specimens are prepared for atom probe tomography (APT) and electro-chemically charged in a solution of 0.1 M NaOH in D 2 O to introduce deuterium (D). D is located at the finely dispersed Cr-carbides even after specimen transfer at room temperature (RT), which shows that nano-sized Cr-carbides are strong H traps. This is in contrast to previous studies of weak traps where cryogenic transfer was needed to detect any D. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal gyrations inherent to metal additive manufacturing (AM) result in complex microstructural heterogeneities that are linked to the process parameters, geometry, and alloy composition. AM 17–4 precipitation hardened (PH) stainless steel displays heterogeneities due to its multi-phase microstructure where different as-built phases have been reported. These phases include austenite, martensite, and ferrite, as well as varying degrees of AM induced Cu clustering and/or precipitation. To enable a systematic study of the evolution of these strengthening phases, we utilize a non-standard concentric scan strategy to achieve variations in thermal conditions across a build. Using atom probe microscopy and thermal modeling, we show that the response of Cu varies across the build from no clustering at the outer regions to an increased tendency for Cu precipitation towards the center. Our results will enable the tuning of processing parameters to achieve homogenous Cu precipitation, and thus improve mechanical properties of AM 17–4 PH. [Display omitted] [ABSTRACT FROM AUTHOR]

Improving hydrogen embrittlement resistance is a prerequisite for expanding the application of high-strength steels. A high-strength deformed pearlitic steel exhibits excellent hydrogen embrittlement resistance presumably because strong hydrogen trapping sites induced by deformation prevent hydrogen accumulation at potential crack initiation sites. This work reports the conclusive identification of the strong hydrogen trapping site in the deformed pearlitic steels. Thermal desorption spectroscopy showed a distinct hydrogen desorption peak at high temperature of ∼ 600 K solely in the deformed pearlite. Scanning transmission electron microscopy and atom probe tomography analyses revealed that the deformation resulted in strain localization at the ferrite/cementite interfaces, together with the formation of a large number of dislocations, leading to the strong segregation of deuterium, a natural isotope of hydrogen, at the interface. Therefore, hydrogen trapping in the deformed pearlitic steels is attributed to the strained ferrite/cementite interface. [Display omitted] [ABSTRACT FROM AUTHOR]

Laser surface remelting can be used to manipulate the microstructure of cast materials. Here, we present a detailed analysis of Fe 2 VAl following laser surface remelting. Within the melt pool, elongated grains grow nearly epitaxially from the heat-affected zone. These grains are separated by low-angle grain boundaries with 1°–5° misorientations. Segregation of vanadium, carbon, and nitrogen at grain boundaries and dislocations is observed using atom probe tomography. The local electrical resistivity was measured by an in-situ four-point-probe technique. A smaller increase in electrical resistivity is observed at these low-angle grain boundaries compared to high-angle grain boundaries in a cast sample. This indicates that grain boundary engineering could potentially be used to manipulate thermoelectric properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The role of elemental partitioning between β and ω phase in embrittling an originally ductile ω-containing Ti–12Mo (wt.%) model alloy was studied using transmission electron microscopy and atom probe tomography. It is revealed that the embrittlement of this alloy already occurs after aging at 400 °C for as short as 10 min, when the size, inter-particle spacing and volume fraction of the ω particles remain almost unchanged. The origin of the aging-induced embrittlement is attributed to the significant rejection of Mo (>5 at.%) from the ω particles during aging, which leads to remarkable increase in the shear modulus (>30 GPa) of the ω particles, promoting intense plastic flow localization and facilitating crack nucleation prior to macroscopic yielding. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The influence of high magnetic field (HMF) during aging on the precipitation behavior of co-precipitates consisted of Cu-rich precipitates and Ni(AlMn) precipitates in multicomponent nano-precipitated steels was carefully investigated. It was indicated that HMF promoted the construction of hierarchical structures of Cu-rich and Ni(AlMn) co-precipitates. It was thought that HMF increased nucleation rates of secondary co-precipitates during aging because of the thermodynamics change, thus refining the secondary precipitates. Meanwhile, HMF increased the Ostwald ripening rate of primary particles during the further aging after tempering because of increasing diffusion of Cu, thus accelerating the coarsening process. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The mechanism of inverse precipitation of γ-like shells forming around primary γ' leading to heteroepitaxial recrystallization after thermomechanical processing was studied. The wrought nickel-based AD730™ alloy was subjected to a sub-solvus heat treatment at 1050°C and cooled at 5°C/min in order to form heteroepitaxial γ-like shells on primary γ'. Electron backscattered diffraction analysis confirmed no measurable crystal misorientation between the γ-like shells and primary γ'. Atom probe tomography revealed segregation of Cr, Co and Fe at dislocations within the primary γ', while the γ-like shell was found enriched in these solutes compared to the γ matrix. A mechanism rationalizing the inverse precipitation of γ-like shells is proposed aiming to better understand the nucleation process of heteroepitaxial recrystallization in polycrystalline Ni-based superalloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

An Al-Si-Cu-based cast alloy was modified with transition metal elements Zr, V and Ti to achieve enhanced mechanical performance at elevated temperatures. Multiple microstructural characterization techniques were used to investigate the solidification segregation behavior of these transition metal elements and their partitioning to the primary intermetallic phases and secondary precipitates. Three transition metal elements were shown to segregate into the dendrite center to varying degrees. Two primary intermetallic phases enriched with different amounts of transition metal elements were identified as D0 22 and D0 23 phases. Zr was observed to concentrate much more than V and Ti in the nano-size secondary L1 2 precipitates, which formed in the matrix during post-solidification heat treatment. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Phase stability of a nanocrystalline CrCoNi alloy is investigated using the combinatorial processing platform approach, which enables synthesis, processing and direct atomic-scale characterizations of alloys by atom probe tomography and transmission electron microscopy. Phase decomposition with formation of CoNi-rich phase occurs faster in the smaller (10 nm) grain-sized region than the larger one (20 nm), both being present in the same sample. Chemical analyses indicate that diffusion of Co and Cr plays an important role in phase decomposition. Comparison of phase stability between CrMnFeCoNi and CrCoNi implies that elemental segregation may promote phase decomposition by providing an additional chemical driving force for it. [ABSTRACT FROM AUTHOR]

High-strength Al-Zn-Mg-Cu alloys are highly susceptible to stress corrosion cracking (SCC) which severely limits their lifetime. Reversion and re-aging (RRA) temper provides a higher SCC resistance at no loss in strength, yet the microstructural origins of these enhanced properties remain elusive. In an Al-Zn-Mg-Cu alloy, we show that the fine precipitate dispersion in the grain interiors is similar in the peak aged and RRA tempers. However, upon RRA, precipitates inside the grains are enriched in Cu, lowering the Cu matrix content, and reducing the relative difference in the Cu precipitate composition between bulk and grain boundaries. This study enriches the current understanding on the critical role of Cu related to SCC resistance in Al-Zn-Mg-Cu alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The behavior of solute atoms in an undersaturated Fe-3.3 at.%Ni model alloy upon heavy and light particle irradiations was investigated by Atom Probe Tomography. Whereas first irradiations, performed using 27 MeV Fe ions at 400 °C, highlight significant Ni enrichment on point defect clusters, solute-rich features detected after 2.8 MeV H + ion (400 °C) and 1 MeV electron (320 °C) irradiations are only associated with pre-existent microstructural defects. Nanoindentation tests show no hardening in light particle irradiated samples, strongly suggesting that no dislocation loop formed. These observations put forward the importance of point defect clusters resulting from displacement cascades in Ni clusters' formation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Misfits of γ-γ' based Al 10 Co 25 Cr 8 Fe 15 Ni 36 Ti 6 and its Mo- and Hf-variations are studied up to a temperature of 980 °C and compared with Ni- and Co-based superalloys. The trace elements decrease (Hf) or increase (Mo) the edge radii of the γ' cuboids without changing their sizes. Atom probe measurements revealed that the Hf alloy prefers the γ' phase while Mo prefers the γ matrix, leading to a lattice parameters enhancement of both phases, as could be revealed by synchrotron X-ray diffraction. The misfit is influenced in opposite ways: Hf increases the positive misfit, while Mo reduces it at all investigated temperatures. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We report achievement of non-Cu-matrix critical current density (J c) in internally-oxidized Nb 3 Sn superconductors that surpasses the best state-of-the-art Nb 3 Sn and the J c specification of the Future Circular Collider. We then explore the mechanism of the improvement, which was believed to be caused by refined grain size. However, our experiment showed that even with similar grain size, internally-oxidized wires had significantly higher J c than non-oxidized wires. This, combined with transmission electron microscopy and atom probe tomography studies which showed a high density of intragranular nano-precipitates with suitable sizes as pinning centers in internally-oxidized wires, demonstrates a significant contribution from the nano-precipitates. Image, graphical abstract [ABSTRACT FROM AUTHOR]

It is critical to control the electrical resistivity of alloys used for wires in harsh environment, e.g. for implanter bio-devices. As-drawn and aged MP35N wires were investigated, exhibiting increasing resistivity with aging time and temperature, in contrast to precipitate-forming alloys. We reveal Cr segregation to deformation twin boundaries upon aging, which effectively facilitates electron scattering and increases the resistivity. Since the diffusion of Cr atoms to these fault planes is rather fast, the larger increment of resistivity occurs very quickly, especially at elevated temperatures. This mechanism is likely active in a wide range of non-dilute alloys that form extended fault planes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A novel Fe–Cr–Ni–Mo weld metal containing different V content was designed and fabricated by gas metal arc welding and post-weld heat treatment. The excellent mechanical properties with a combination of high strength and good toughness were obtained by synergistic effect of nanoscale carbides, high-density dislocations and small subgrains. The discrete nanoscale carbides were characterised by transmission electron microscopy and atom probe tomography. Moreover, it was firstly found that the precipitation sites of nanoscale carbides were mainly located at inter-dendritic regions instead of dendritic core regions owing to the heterogeneous distribution of alloying elements. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We have studied the large-scale plasticity assisted topological inversion in a Ni-based superalloy after creep at 850 °C. Multi-scale characterization from the micro- to the near-atomic scale was used to unravel the processes governing topological inversion of a Ni-based single crystal superalloy and reconstruct the resulting three-dimensional microstructure. A plasticity assisted redistribution of interacting solutes mechanism, where shearing dislocations mass-transport solutes, is proposed to explain the transition from a rafted to intricately interconnected (inverted) structure. The interplay between microstructural evolution and mechanical behavior is discussed in terms of applied stress and microstructural features, relating atomic-scale processes to macro-scale behavior. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Fe 2 VAl exhibits promising properties for thermoelectric applications. Here, we investigated the microstructure of melt spun Fe 2 VAl using electron microscopy, atom probe tomography and field ion microscopy. We observe platelet-shaped VC x N y precipitates in the vicinity of antiphase boundaries (APB) oriented along the {100}-plane. The mean distance between these precipitates is (140 ± 40) nm. This distance is shorter than the mean free phonon path at room temperature in Fe 2 VAl. Thus, these VC x N y precipitates, combined with the APB may efficiently lower the thermal conductivity of the alloy. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A new set of half-Heusler high-entropy alloys Ti 2 NiCoSn 1-x Sb 1+ x (x = 0.5, 1), with a valence electron count higher than 18, were investigated for thermoelectric applications. Vacuum arc melting was employed for synthesis. Atom probe analysis confirmed single-phase at atomic level. The alloys were subsequently ball milled for 1 h followed by spark plasma sintering for consolidation. In 1 h BM cases, the alloy with x = 0.5 exhibited a low lattice thermal conductivity of 2.48 Wm−1K−1, and a ZT of 0.29 at 873 K. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Industrial scale single crystal (SX) Ni-base superalloys contain numerous low angle grain boundaries inherited from the solidification process. Here, we demonstrate that low angle grain boundaries in a fully heat-treated SX model Ni-base superalloy are strongly segregated with up to 12 at% Re. Some Re-rich dislocations forming this grain boundary are found located inside γ, others close to a γ/γ′ interface. Although these segregated Re atoms lose their solid-solution strengthening effect, they may enhance the creep resistance by pinning the low angle grain boundaries and slowing down dislocation reactions. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Atom Probe Tomography is used to show that the α 2 phase (Ti 3 Al) forms upon ageing Ti–7Al at 550 °C with as little as 500 wppm oxygen. Notably, it is found that oxygen consistently partitions away from the α 2 precipitates to the α matrix. The role of aluminium concentration and oxygen solubility on oxygen partitioning preference is also investigated. Based on our observations, we propose a mechanism by which oxygen encourages α 2 formation despite partitioning away from it. Furthermore, nanohardness systematically measured with respect to ageing time and oxygen concentration suggests that α 2 precipitation is not the dominant hardening mechanism during ageing. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Based on our recently-developed combinatorial processing platforms for accelerated investigations of phase evolution in multinary alloys, a novel correlative atom probe tomography and transmission electron microscopy approach is proposed to study phase stability in a nanocrystalline CrMnFeCoNi alloy. We observed that the material can decompose at 250 °C for 5 h or 300 °C for 1 h, having the same decomposed products as in its coarse-grained counterpart after annealing at 500 °C for 500 days. A low apparent activation energy for the diffusion of Ni in the nanocrystalline alloy is derived and explains the fast kinetics of phase decomposition in nanocrystalline alloys. [ABSTRACT FROM AUTHOR]

The microstructure and magnetic properties of three face-centered cubic (FCC) FeCoNiCrCu(x) high entropy alloys (HEAs) (x = 0, 0.5, 1) are investigated. Interestingly, addition of the nonmagnetic element Cu to FeCoNiCr HEA is found to enhance exchange interactions and low temperature saturation magnetization. The paramagnetic to ferromagnetic Curie transition temperature increases from 85 K for FeCoNiCr to 118 K for FeCoNiCrCu. This is counterintuitive since Cu is nonmagnetic; however, atom probe tomography revealed Cu rich clusters containing 5 at% Ni and 1 at% each of Fe, Co, Cr, within FCC matrix, these clusters altered the matrix composition and consequently its magnetic properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The solute partitioning under dynamic strain-induced austenite reversion in a Fe-11Mn-1Al-0.07C (in wt.%) steel was studied by atom probe tomography. It was found that the concentrations of Mn and Al fluctuate in austenite at the nanoscale during warm deformation at 650 °C, leading to less stable chemical zones. It is proposed that stored energy in ferrite can change the thermodynamic equilibrium, leading to the formation of austenite with lower Mn and higher Al contents. This paper reveals evidence that stored strain can deviate the thermodynamic equilibrium, and hence could be a new path for engineering the nanostructures in austenite. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The nanostructure of an Fe0.65Cr0.35 alloy has been investigated by atom probe tomography after high-precision thermal treatments close to the upper limit of the miscibility gap (MG). It is found that the wavelength of the decomposed ferrite between Cr- and Fe-rich regions grows exponentially when approaching the upper limit of the MG. Furthermore, the nanostructure change is gradual with temperature indicating a narrow metastable region and a diffuse transition out of the spinodal regime. Atomistic modelling near the limit of instability further supports the experimental observations. The findings are discussed in relation to the Cahn-Hilliard theory. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A nano-scaled shuffle-induced modulated structure and heating-induced ordering have been characterized in a metastable β-titanium alloy, Ti-5Al-5Mo-5V-3Cr, and their inter-relationship was investigated through in-situ and ex-situ conventional and aberration-corrected scanning/transmission electron microscopy and atom probe tomography. The nano-scaled O′ phase with a disordered orthorhombic-modulated structure formed by the { 011 } < 01 1 ¯ > β transverse phonon was characterized for the first time to be stable from room temperature to ∼200°C. The O″ phase with an ordered orthorhombic structure formed from the β phase during aging above the O′ phase solvus temperature, where Al segregation in nano-scaled regions led to ordering of every third {011} planes. Image, graphical abstract [ABSTRACT FROM AUTHOR]

It is often assumed that internal oxidation cannot occur at temperatures below 400 °C. However, in the present work, internal oxidation was observed in a 20% cold-worked Fe-17Cr-12Ni stainless steel (SS) after exposure to simulated primary water of a pressurized water reactor at 340 °C and not in a similarly tested sample without prior cold-work. The formation of discrete Cr-oxide precipitates and the role of cold-work are discussed. The internal oxidation model is also proposed as a plausible stress corrosion cracking mechanism of Fe-17Cr-12Ni SS at that temperature. Unlabelled Image [ABSTRACT FROM AUTHOR]

Partitioning of C during tempering of quenched Fe-9.6Ni-0.5C-0.6Mn-0.6Mo-0.7Cr-0.1V (at.%) steel is determined by atom probe tomography and the resulting microstructure is described. The precipitated austenite size, together with its C and Ni content control its thermal stability and these can vary differently with tempering time and temperature. Thus, both austenite and strong carbide formers compete for the available C early in the process. Due to widely different transport kinetics, C likely plays a dominant role early but is either fully consumed or its role diminishes by dilution, and Ni partitioning eventually takes over as the austenite stability-controlling species. Unlabelled Image [ABSTRACT FROM AUTHOR]

The successful development of advanced materials such as nanostructured ferritic alloys (NFA) for next generation nuclear reactor concepts and ultra-supercritical steam power plants requires information on long term thermal creep. To support this initiative, this work examines the NFA MA957 (Fe-14Cr-1.0Ti-0.3Mo + 0.3Y 2 O 3 in wt%) crept to 61,251 h at 825 °C and 70 MPa, the longest creep test available to date for this material. Using atom probe tomography and electron microscopy, it is shown that the grain size and nanoprecipitate size/composition are unaffected following this 7 yr creep test, although significant porosity is noted throughout the microstructure attributed to microvoid coalescence and growth. Unlabelled Image [ABSTRACT FROM AUTHOR]

The structure and chemistry of the orthorhombic O′ phase after quenching of a Ti-23 at.%Nb-2 at.%O was measured using aberration-corrected transmission electron microscopy and atom probe tomography. The nanosized O′ phase, formed in the vicinity of ω, is enriched with oxygen and slightly depleted in Nb. Upon annealing, ω dissolves and the O′ phase develops in β up to 350 °C, above which temperature it transforms to colonies of fine α phase. Another needle-like form of α with lower Nb content is thought to nucleate from Nb-lean regions related to spinodal decomposition of β. Unlabelled Image [ABSTRACT FROM AUTHOR]

Homogeneous distribution of the constituent elements at the atomic scale in high entropy oxides (HEOs) was demonstrated for the first time by atom probe tomography (APT). Three different single-phase HEOs having rocksalt, fluorite, and perovskite type crystal structures were synthesized using nebulized spray pyrolysis process. The as-synthesized powders were compacted into pellets under high pressure of 6 GPa. Both as-synthesized and compacted powders were investigated by X-ray diffraction and transmission electron microscopy. APT results showed that the constituent cations in all three HEO systems were homogenously distributed with no significant segregation or concentration fluctuation even at the atomic scale. Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract We demonstrated the use of three-dimensional (3D) atom-probe tomography (APT) for analyzing the electrochemical lithiation/delithiation in the composite cathodes of all-solid-state batteries (ASSBs). 3D APT provides direct determination of the Li-ion contents, having difficult by X-ray excitation. Compared with various cathodes, they showed a significant variation in the Li-ion concentration during lithiation/delithiation because of the poor solid-to-solid interfaces, which is an inherent problem in ASSBs. In addition, the loss of transition-metal content was quantitatively verified. We have confirmed that our APT can be effectively applied to ASSB systems and it would be provide a deeper understanding of electrochemistry in ASSBs. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract It is well known the effectiveness of ausforming on increasing the dislocation density of fresh martensite. This work demonstrates, using atom probe tomography, that this increase in the dislocation density has a strong influence on the nucleation of nanoprecipitates during tempering. Therefore, ausforming might be a powerful processing route for the two-fold improvement of ferritic/martensitic steels where creep resistance is of paramount importance. Firstly, ausforming refines the martensitic microstructure (high strength and toughness), and secondly, it increases the number density of thermally stable nanoprecipitates (creep resistance). Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract The high-entropy alloy (HEA) composite Al 0.3 CoCrFeMnNi based on the face-centered-cubic (FCC) system and reinforced with 0–3 vol% Y 2 O 3 was processed by mechanical alloying followed by spark plasma sintering (SPS). The compressive yield strength of the Al 0.3 CoCrFeMnNi high-entropy alloy (HEA) increased phenomenally, from 0.98 GPa (0 vol% Y 2 O 3) to 1.76 GPa (3 vol% Y 2 O 3). A quantitative analysis by atom probe tomography (APT) suggested the in-situ formation of complex oxide resulting from the reaction of Y 2 O 3 with the HEA matrix during processing, enhancing the strength. Using the dispersion-barrier hardening model, the strengthening by dispersoids in Al 0.3 CoCrFeMnNi with Y 2 O 3 was calculated, and closely matched the experimental results. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Ingress of hydrogen is often linked to catastrophic failure of Ti-alloys. Here, we quantify the hydrogen distribution in fully β and α + β Ti Mo alloys by using atom probe tomography. Hydrogen does not segregate at grain boundaries in the fully β sample but segregates at some α/β phase boundaries with a composition exceeding 20 at.% in the α + β sample. No stable hydrides were observed in either sample. The hydrogen concentration in β phases linearly decreases from ~13 at. % to ~4 at. % with increasing Mo-content, which is ascribed to the suppression of hydrogen uptake by Mo addition. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Atom Probe Tomography (APT) was used to obtain a direct evidence of chlor segregation and cobalt diffusion at the grain boundaries (GBs) of polycrystalline coatings deposited by moderate temperature chemical vapor deposition (MT-CVD) on a WC-Co cemented carbide substrate. Reasons behind segregations are discussed, and its effects are correlated to the micromechanical properties of Ti(C,N) and Zr(C,N). It is concluded that chlorine segregation is a relevant factor for explaining the low cohesive strength at the GBs of Ti(C,N) leading to intergranular failure during micro-compression testing, while its absence in Zr(C,N) along with Co diffusion contribute to grain boundary strengthening. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Using a combination of numerical simulations and atom-probe tomography experiments, we determine the interfacial energy of Cu nanocrystals precipitated within the amorphous matrix of FINEMET (molar composition Fe 72.89 Si 16.21 B 6.90 Nb 3 Cu 1). Specifically, we use the Langer-Schwartz model implemented in the software Thermocalc to carry out parametric simulations of growth and coarsening of Cu clusters for different interface energies. We have carried out atom-probe tomography (APT) experiments to determine the interface energy as the value for which the simulated particle size distribution best matches the experimental data. This combination of APT and precipitation modeling can be applied to other nanocrystals precipitated within amorphous matrices. Graphical abstract Description: Cu cluster size distributions simulated for different values of the interface energy γ (curves), compared with the distribution obtained from APT (blue histogram). Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract The alloying elements partitioning from martensite to austenite during quenching and partitioning was analysed by coupling in situ High Energy X-Ray Diffraction experiments and 3D atom probe tomography. A rapid and significant carbon partitioning from martensite to austenite without any partitioning of both Mn and Si was highlighted while the interface was immobile. After a relatively short time at 400 °C, a clear Mn partitioning occurs at the vicinity of the α′/γ interface. The analysis conducted indicates that manganese equilibrates its chemical potential during partitioning and raises the issue of the Constrained Carbon Equilibrium model applicability throughout the partitioning process. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Oxide dispersion strengthened (ODS) FeCrAl alloy (Fe-12Cr-5Al wt%) was neutron irradiated to 1.8 displacements per atom (dpa) at 215, 357, and 557 °C to investigate (Y,Al,O) nano-oxide stability and Cr-rich α ′ precipitate formation using atom probe tomography. The nano-oxide sizes remain unchanged after irradiation, but the compositions are dependent on irradiation temperature due to competition between ballistic dissolution and precipitate reformation. Cr-rich clusters observed after 357 °C irradiation have lower Cr contents (61 at.%) than equilibrium α ′, with a lower number density than wrought FeCrAl alloys. This suggests a suppression of α ′ precipitation due to the high sink strength of ODS FeCrAl. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract The effect of phosphorous on the microstructure of a powder-processed, high Nb-content, Ni-based superalloy was studied and compared to a P-free variant. The P-doped sample had a lower incipient melting temperature, forming a (Ni, Co, Cr, P) 2 (Nb, Mo) laves phase along the grain boundaries. Transmission electron microscopy and atom probe tomography were used to identify the crystal structure, assess phase compositions, and determine any elemental segregation to phase boundaries. The results revealed strong partitioning of P to the laves phase and a slight Mo gradient towards the γ′ phrase. Finally, a simplified laves phase was successfully modeled via density functional theory calculations. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Carbide precipitates are pivotal for strengthening steels and improving their resistance to hydrogen-embrittlement. Combining aberration-corrected high-resolution transmission electron microscopy and atom probe tomography, this work provides an atomic-scale evidence for the precipitation mechanism from embryo cluster to nano-precipitate in ferritic steels. Carbide precipitation begins with disc-shaped embryo clusters of several atom layers thick, which are fully coherent with the ferrite matrix. As the diameter increases, the embryo clusters grow into clusters that are analogous to the Guinier-Preston zone in Aluminium alloys. With further increase in size, particularly in thickness, clusters transform into a new phase with NaCl-structure. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract We report on the full three-dimensional compositional partitioning among the features of a planar imperfection comprising a superlattice intrinsic stacking fault (SISF) with its leading and trailing partials, as well as the antiphase boundary (APB) in the wake of the trailing partial formed in the L1 2 -ordered γ′ phase of a CoNi-based single crystal superalloy. The partial dislocations and the APB are found to be Cr/Co rich relative to the surrounding γ′ and richer in W/Ta/Ti compared to the γ matrix phase. Solute diffusion mechanisms are derived from the compositional gradients in the vicinity of the imperfection. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Zircaloy-4 (Zr-1.5%Sn-0.2%Fe-0.1%Cr wt%) was electrochemically charged with deuterium to create deuterides and subsequently analysed with atom probe tomography and scanning transmission electron microscopy to understand zirconium hydride formation and embrittlement. At the interface between the hexagonal close packed (HCP) α-Zr matrix and a face centred cubic (FCC) δ deuteride (ZrD 1.5–1.65 ), a HCP ζ phase deuteride (ZrD 0.25–0.5 ) has been observed. Furthermore, Sn is rejected from the deuterides and segregates to the deuteride/α-Zr reaction front. [ABSTRACT FROM AUTHOR]

The influence of grain boundary Cr carbides on the intergranular oxidation behavior of a Ni-16Cr alloy is considered using atomistic-to-mesoscale model and atom probe tomography. Cr carbide strongly perturbs the collective reactive dynamics of oxidizing species and alloy elements in the intergranular region. Strong attractive interactions between oxygen and carbide create a driving force for Cr and Ni accumulation in the grain boundary adjacent to the carbide, and for the depletion of Cr and Ni ahead of the oxidation front beyond the carbide. The results shed light on the mechanism of carbide-assisted protection of the alloy against grain boundary corrosion/oxidation. [ABSTRACT FROM AUTHOR]

Mg alloys containing long-period stacking ordered (LPSO) structures are strong and ductile compared to conventional Mg alloys. We study here the compositional evolution of LPSO structures in a Mg97Y2Zn1 (at.%) alloy upon annealing at 500 °C using atom probe tomography. In the material annealed for 2.5 h, the Zn/Y ratio of the building blocks in the interdendritic LPSO phase (0.73) is close to the stoichiometric composition of Y 8 Zn 6 L1 2 clusters while that in plate-type LPSO structures (0.66) slightly deviates from the ideal value. The Y/Zn enrichment in LPSO structures in the α-Mg matrix slightly decreases with increasing annealing time. [ABSTRACT FROM AUTHOR]

The characteristics of grain boundaries and their influence on the mechanical properties have become key issues in recent research on structural materials. Especially in molybdenum, grain boundary segregation plays a significant role regarding ductility and strength. In this study as-sintered conditions of technically pure as well as boron and carbon doped molybdenum were mechanically characterized by bending tests and correspondingly analyzed by atom probe tomography to understand the differences in mechanical behavior after alloying. Strategies for improving the ductility of molybdenum are discussed with special focus on grain boundary segregation. [ABSTRACT FROM AUTHOR]