Metallic materials with nanolamellar structures, such as pearlitic steels, exhibit high strength with appropriate ductility. Considering the potential ability of such nanolamellar structures to break the traditional strength-ductility trade-off in metallic alloys, this study aims at developing a unique nanolamellar structure with superior micromechanical properties by combining two different high-entropy alloys (HEAs). Al0.1CoCrFeNi with the face-centered cubic (FCC) structure is combined with TiZrHfNbTa with the body-centered cubic (BCC) structure using high-pressure torsion (HPT) of half discs of each phase. That way, a layered hybrid structure was formed, with layer thickness down to about 61nm. The BCC/FCC nanolamellar hybrid structure exhibits an exceptional combination of properties with an ultimate tensile strength of 2.4GPa, a maximum bending strength of 4.0GPa, and a hardness of 740 Hv, while retaining some ductility/plasticity under both tensile and bending loads. Detailed analyses by synchrotron diffraction, electron microscopy and atom probe tomography suggests that these high strength and hardness, which are superior to those of nanostructured HEAs result from: (i) extreme grain boundary strengthening from nanograins with a mean size of 22nm, (ii) presence of defects such as dislocations in FCC and BCC, stacking faults in FCC and twins in FCC, and (iii) interphase hardening from BCC/FCC nanolamellar boundaries with about 30% contribution to the total hardness. This work demonstrates that combining two HEAs using HPT into a defect-rich hybrid nanolamellar composite forms a promising synergy of ultrahigh strength and reasonable ductility/plasticity by developing defect-rich hybrid nanolamellar structures.

This study presents tensile properties of Al-Mg-Si alloys after processing by severe plastic deformation through high-pressure torsion (HPT). The alloys were fabricated so as to include excess Fe and Si with different additions of Cu as model alloys for recycling purpose. The tensile strength well exceeded 500 MPa with the total elongation more than 15% after HPT-processing under 2 GPa for 1 turn in all the model alloys. The strength further increases to more than 700 MPa with increasing addition of Cu while maintaining reasonable ductility (similar to 8%). Transmission electron microscopy confirmed that the grain size was reduced to 180 nm and further reduced to 160 nm with increasing Cu addition. Micros structural analyses using scanning transmission electron microscopy and atom probe tomography revealed that Cu was segregated at grain boundaries, contributing to the increase in the tensile strength. The high strength with enhanced ductility is discussed in terms of strain rate sensitivities measured from strain rate change tests.

Abstract Transmission electron microscopy (TEM) is a classical characterisation technique for the investigation of microstructures in metallic alloys. In-situ TEM experiments, where an external stimulus is exerted on the sample, allow the investigation of dynamic structural changes. The possibilities and the limitations of in-situ TEM for the experimental study of thermally induced boundary motion and interaction with particles are presented based on data collected for three different systems. At first, the role of nanoscaled intermetallic particles on the thermal stability of a severely deformed Al alloy is discussed. Then, the influence of the TEM sample surfaces (thin foil effect) on grain growth is illustrated with an ultrafine-grained nickel sample. Finally, the direct observation of dynamic interactions between an Al/Al 2 Cu interface and nanoscaled particles during the growth of Al 2 Cu is presented.

The influence of hydrogen on the precipitation kinetics of L12-Al3Zr ordered precipitates in an industrial Al-Zr alloy was investigated using transmission electron microscopy (TEM) and atom probe tomography (APT). Aging at 375 degrees C under 10 MPa of hydrogen led to a significant acceleration of Al3Zr precipitate growth, a larger mean precipitate size compared to aging in air, and an enhanced decomposition of the supersaturated solid solution. Fitting experimental data with a coarsening model suggests that hydrogen increases the diffusion coefficient of Zr by a factor of two, likely due to hydrogen-vacancy interactions promoting the mobility of Zr.

Austenitic stainless steels utilized in-core components of pressurized water reactors are prone to radiationinduced segregation, which leads to the degradation of microstructure and mechanical properties. To improve irradiation resistance, one possible solution is to increase the number density of point defect sinks, such as grain boundaries. For this purpose, ultrafine-grained or nanostructured microstructures are recommended due to their high density of grain boundaries. This paper investigates the microstructural changes in ultrafine-grained 316 austenitic stainless steel exposed to neutron radiation up to 3.9 dpa in irradiation conditions representative of light water reactors. The microstructure at different length scales was analyzed using electron backscattered diffraction, transmission electron microscopy, and atom probe tomography before and after neutron irradiation. The study compares its findings with those of existing literature on coarse-grained austenitic stainless steels to evaluate the benefit of ultrafine-grained 316 austenitic stainless steels regarding irradiation ageing in representative conditions of light water reactors.

Ultrafine-grained aluminum alloys are of interest due to their high strength-to-weight ratio, but they usually suffer from poor uniform ductility. In this study, an Al-Au alloy with a good combination of strength and ductility is produced by the heterogeneous distribution of Al2Au nanoparticles in an aluminum matrix. To generate such heterogeneity, the alloy is synthesized by ultra-severe plastic deformation of aluminum and gold powders via the high-pressure torsion method. Reactive interdiffusion occurs during the process leading to the heterogeneous formation of intermetallic particles and a good strength-ductility synergy (200 MPa yield stress and 15% uniform elongation). Nanoparticles gradually distribute within the matrix and once a uniform nanoparticle distribution is achieved, the alloy shows no further increase in strength, but it completely loses its ductility. It is concluded that not only the presence of nanoparticles but more importantly the heterogeneity of their distribution can positively influence the strength-ductility combination in ultrafine-grained aluminum alloys. The findings of this study suggest that future studies on heterogeneous precipitation hardening can be a solution to achieve ductile precipitation-hardened alloys.

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.

The dislocation configurations of a Ti2AlC-MAX phase deformed under severe plastic deformation by surface mechanical attrition treatment have been analyzed by transmission electron microscopy. Results show that the microstructure of the deformed Ti2AlC sample is composed of numerous (a)-dislocations, which interact with each other notably with dipolar configurations. In addition, we report here (a)-dislocation dissociations in the basal plane with a dissociation distance of approximately 20 nm, following the reaction 31 (2110)<#.31 (1100) + 3 (1010). Finally, evidence of zonal dislocations is reported. These original results are discussed in the context of 1 the fundamental deformation mechanisms of nanolayered ternary alloys.

Mainly constituted of glycosaminoglycans and proteoglycans, the glycocalyx is anchored in the plasma membrane, covering, in particular, the extracellular face of the arterial endothelium. Due to its complex three-dimensional (3D) architecture, the glycocalyx interacts with a wide variety of proteins, contributing to vascular permeability, the flow of mechanotransduction, and the modulation of local inflammatory processes. Alterations of glycocalyx structure mediate the endothelial dysfunction and contribute to the aggravation of peripheral vascular diseases. Therefore, the exploration of its ultrastructure becomes a priority to evaluate the degree of injury under physiopathological conditions and to assess the impact of therapeutic approaches. The objective of this study was to develop innovative approaches in electron microscopy to visualize the glycocalyx at the subcellular scale. Intravenous perfusion on rats with a fixing solution containing aldehyde fixatives enriched with lanthanum ions was performed to prepare arterial samples. The addition of lanthanum nitrate in the fixing solution allowed the enhancement of the staining of the glycocalyx for transmission electron microscopy (TEM) and to detect elastic and inelastic scattered electrons, providing complementary qualitative information. The strength of scanning electron microscopy (SEM) was used on resin-embedded serial sections, allowing rapid and efficient large field imaging and previous correlative TEM observations for ultrastructural fine details. To demonstrate the dynamic feature of the glycocalyx, 3D tomography was provided by dual-beam focus-ion-beam-SEM (FIB-SEM). These approaches allowed us to visualize and characterize the ultrastructure of the pulmonary artery glycocalyx under physiological conditions and in a rat pulmonary ischemia-reperfusion model, known to induce endothelial dysfunction. This study demonstrates the feasibility of combined SEM, TEM, and FIB-SEM tomography approaches on the same sample as the multiscale visualization and the identification of structural indicators of arterial endothelial glycocalyx integrity.

Novel materials with neutron shielding property were fabricated by incorporating boron compounds into high-density polyethylene (HDPE)/Ethylene propylene diene monomer rubber (EPDM) blends. A detailed investigation on the morphological, thermal, mechanical, and neutron attenuation properties of suitable proportion of HDPE/EPDM blend with boric acid (BA), boron carbide (BC), and nano boron carbide (NBC) were performed. Morphology of the 20 wt% of EPDM shows better distribution in HDPE matrix. BA filler is localised in the HDPE phase, while NBC shows uniform distribution in HDPE/EPDM blend compared to its micro counterpart. There is a reduction in the tensile strength and modulus with the incorporation of EPDM in HDPE, whereas the ductility of HDPE is enhanced. A significant increase in the tensile toughness of the HDPE/EPDM blend with lower tensile strength and modulus is observed for BA, and BC filled composites. Moreover, HDPE/EPDM composites with NBC show only a marginal increase in the tensile toughness, tensile strength, and modulus. Comparison of the Young's modulus of the HDPE/EPDM blends with theoretical models indicates trends similar to the Coran model. The BA and BC filled composites follow the lower bound series model, whereas NBC composites show behaviour similar to the Halpin Tsai model. Total thermal neutron macroscopic cross-section (0.025 MeV energy neutrons) of 10 cm(-1) and mean free path of 0.1 cm was obtained for 20 wt% NBC HDPE/EPDM composites.

Fe–Ga alloys, containing 18, 21, and 23 at.% of Ga, were prepared in bulk form. In their as-cast state, they display a small magnetostriction, that is strongly improved after annealing at 1000 °C for 24 h, and subsequent rapid cooling. Multiple characterization techniques, such as x-ray diffraction, differential scanning calorimetry, Mössbauer spectroscopy, temperature-dependent magnetization curves, hysteresis loops, magnetic force microscopy, and magnetostriction measurements, were exploited in synergy to gain a deep understanding of the structure–property relationships in the studied alloys, before and after annealing. The A2 phase, which is favored in the lower range of compositions and is promoted at the expense of the D03 one by annealing, is responsible for characteristic dendritic and maze magnetic domains, and for the strong improvement of the magnetostriction, which almost reaches 240 ppm (transverse configuration) in the alloys with 18 at.% of Ga, after annealing.

A position-energy-sensitive detector has been developed for APT instruments in order to deal with some mass peak overlap issues encountered in APT experiments. Through this new type of detector, quantitative and qualitative improvements could be considered for critical materials introducing mass peak overlaps, such as nitrogen and silicon in TiSiN systems, or titanium and carbon in cemented carbide materials. This new detector is based on a thin carbon foil positioned on the front panel of a conventional MCP-DLD detector. According to several studies, it has been demonstrated that the impact of ions on thin carbon foils has the effect of generating a number of transmitted and reflected secondary electrons that mainly depends on both the kinetic energy and the mass of incident particles. Despite the fact that this phenomenon is well known and has been widely discussed for decades, no studies have been performed to date for using it as a mean to discriminate particles energy. Therefore, this study introduces the first experiments on a potential new generation of APT detectors that would be able to resolve mass peak overlaps through the energy-sensitivity of thin carbon foils.

In this study, the formation of a periodic microstructural pattern designed by laser powder bed fusion (LPBF), commonly called selective laser melting (SLM), of an AlSi10Mg alloy is revealed at high resolution using scanning transmission electron microscopy and atom probe tomography. Special attention is paid to the description of non-equilibrium structures and compositional fields resulting from the ultrafast cooling of the LPBF process. Observations reveal the existence of a glass state in eutectic areas, wherein short-range ordering of the diamond-Si structure is observed. The apparent very fast solidification of eutectic regions is found to involve a local strain in adjacent Al cells, which extends up to 100 nm on average. In the supersaturated aluminium solid solution retained by the LPBF process, two populations of clusters are identified, for which the potential role of the selection of hardening phases is discussed. It is proposed that the microstructure of former melt pools outside heat-affected areas is described by the repetition of a periodic microstructural pattern consisting of eutectic regions /strain-hardened Al-crystals /strain-free Al-crystals with a high density of solute-rich clusters.

Achieving a combination of high mechanical strength and high electrical conductivity in low-weight Al alloys requires a full understanding of the relationships between nanoscaled features and physical properties. Grain boundary strengthening through grain size reduction offers some interesting possibilities but is limited by thermal stability issues. Zener pinning by stable nanoscaled particles or grain boundary segregation are wellknown strategies for stabilizing grain boundaries. In this study, the Al-Ca system has been selected to investigate the way segregation affects the combination of mechanical strength and electrical resistivity. For this purpose, an Al-Ca composite material was severely deformed by high-pressure torsion to achieve a nanoscaled structure with a mean grain size of only 25 nm. X-ray diffraction, transmission electron microscopy and atom probe tomography data revealed that the fcc Ca phase was dissolved for large levels of plastic deformation leading mainly to Ca segregations along crystalline defects. The resulting microhardness of about 300 HV is much higher than predictions based on Hall and Petch Law and is attributed to limited grain boundary mediated plasticity due to Ca segregation. The electrical resistivity is also much higher than that expected for nanostructured Al. The main contribution comes from Ca segregations that lead to a fraction of electrons reflected or trapped by grain boundaries twice larger than in pure Al. The two-phase state was investigated by in-situ and exsitu microscopy after annealing at 200 degrees C for 30 min, where precipitation of nanoscaled Al4Ca particles occurred and the mean grain size reached 35 nm. Annealing also significantly decreased electrical resistivity, but it remained much higher than that of nanostructured pure Al, due to Al/Al4Ca interfaces that reflect or trap more than 85% of electrons.

this paper presents experimental short-circuit aging tests of a 600V GaN (Gallium nitrite) GIT (Gate Injection Transistor). The short circuit aging tests effect under the drain voltage equal to 35V and the three short-circuit durations (1ms, 2ms and 4ms) are investigated. The evolution of the electrical characterizations is well shown in this paper. A microscopic analysis, related the degradation mechanism, is proposed in the paper.

Intergranular segregation in a Fe-P-C model alloy after thermal ageing at 650 degrees C has been examined using Atom Probe Tomography (APT) and Auger Electron Spectroscopy (AES). The specimens were prepared using site-specific method combining focused ion beam (FIB) and Transmission Kikuchi Diffraction (TKD). Grain boundary's five macroscopic degrees of freedom (DOFs) were determined from the TKD map supplemented by 3D APT reconstruction. The phosphorus intergranular segregation values obtained using APT and AES techniques were in excellent agreement and equal to 1.6 +/- 0.7 at/nm(2) and 1.4 +/- 0.5 at/nm(2), respectively. The two techniques are complementary for a fully quantitative description.

Low-dose (2 at.%) Fe implantation in 6H-SiC (0001), followed by high-temperature annealing, is investigated with the aim of obtaining a diluted magnetic semiconductor (DMS). The effects of rapid thermal annealing on the microstructure were examined by atom probe tomography. The study shows the evidence of the formation of nanoclusters after annealing, some of which are magnetic. The structural study is correlated with the magnetic properties in order to determine the optimum conditions for fabricating a DMS.

Ageing tests through thermal storage at high temperature (240 degrees C) are carried out on commercial Schottky diodes in TO220 package, in "derating mode" operational conditions. The analysis revealed a failure mechanism, resulting into vaporization of the moisture present in significant quantity in the resin/sole interface. As a consequence, a degradation of the resin, freeing up space, caused the solder to spread under the chip. The X-ray analyses, acoustic microscopy SAM, optical and electron microscopy are used to describe the failure mechanism. We note that the resin package has undergone a strong degradation. Investigations show that this phenomenon is fully responsible for the degradation process taking place in derating mode use. Most components behave similarly with respect to the ageing; however, an atypical and unusual result is revealed for one component after the ageing process. Thus, the specific case is presented as a potentially decisive case for the validation of a failure analysis, so that technical solution can be formed.

Scanning electron microscopes (SEM) equipped with focused ion beam (FIB) column are nowadays dual platform instruments commonly used in various micro sample preparation processes. While the mainstream of FIB usage remains within the semiconductor industry, it has expanded to a wide range of materials in metallurgical research. In particular, FIB milling capabilities are today used in the area of advanced materials for nuclear applications, involving in most cases the manipulation of activated samples. Sputtering of radioactive materials is far from trivial and numerous questions remain still open to guarantee the user safety even if small volumes of matter are generated by FIB milling [1]. For instance, where does the FIB sputtered matter accumulate in the SEM chamber? Angular distributions of FIB sputtered atoms have been investigated for 0°, 30° and 54° ion beam incidence. FIB patterns have been milled on a nanocrystalline Nickel alloy using a 30 keV Ga + ion bombardment in a scanning electron microscope (Fig 1a). Sputtered matter is collected on a silicon planar collector. The thickness of the deposit on the collector is measured by means of Z‐contrast imaging and two dimensional spatially resolved thickness maps are drawn (Fig 1b and Fig 1c). Angular distributions of sputtered atoms, in a plane containing the primary ion beam, are deduced from the maps (Fig 3). Our experimental data show that, at oblique incidence, sputtering matter is emitted in two main emission directions, normal to the target surface and towards the FIB column. For normal incidence, all the sputtered matter is projected towards the FIB column. The microstructure of the deposit, at normal incidence, has been studied by Transmission Electron Microscopy and Atom Probe Tomography (Fig 2).