FeCrAl alloys are among the best and most mature accident tolerant fuel cladding candidates produced to date, due to their superior combination of mechanical properties and stability at elevated temperatures. For fuel cladding applications, these materials are drawn into tubes with plugs welded to the ends. The mechanical properties of such welds and the impact on cladding performance have not been fully investigated. A novel mesoscale mechanical test and a variety of microscale tests were performed to evaluate a range of properties including nanoindentation hardness, compression and shear yield strengths, and tensile strengths and elongations. Micromechanical testing generally matched the trends of the larger mesoscale testing, with nanoindentation reproducing the trend the best, although some discrepancies existed in regions with low dislocation content. Mesoscale tensile testing showed good correlation with macroscale tests and revealed that the plug heat-affected zone possessed the lowest strength and ductility. This indicated that failure would occur first in or near this region.

Depth-sensing transmission electron microscopic (TEM) in situ mechanical testing has become widely utilized for understanding deformation in irradiated materials. Until now, compression pillars have primarily been used to study the elastic properties and yield of irradiated materials. In this study, we utilize TEM in situ compression pillars to investigate plastic deformation in two ion-irradiated alloys: Fe–9% Cr oxide dispersion strengthened (ODS) alloy and nanocrystalline Cu–24% Ta. We develop an algorithm to automate the extraction of instantaneous pillar dimensions from TEM videos, which we use to calculate true stress–strain curves and strain hardening exponents. True stress–strain curves reveal intermitted plastic flow in all specimen conditions. In the Fe–9% Cr ODS, intermitted plastic flow is linked to strain bursts observed in TEM videos. Low strain hardening or strain softening is observed in all specimen conditions. TEM videos link the strain softening in irradiated Fe–9% Cr ODS to dislocation cross-slip, and in Cu–24% Ta to grain boundary sliding.

Soyarslan et al. [J. Mater. Res. 33(20), 3371 (2018)] proposed a beam-finite element model for the computation of effective elastic properties of nanoporous materials, where the ligament diameter along the skeleton is determined with the biggest sphere algorithm. Although this algorithm is often used in the literature, it is known that it systematically overestimates the diameter in network structures. Thus, the need for further stiffening of the junction zones as proposed by the authors is in contradiction to the literature. Furthermore, the factor 40 appears to be one order of magnitude too high. We show that the 3D microstructures generated from random Gaussian fields contain features that are violating the assumption of circular cross-sections and, therefore, cannot be captured by the biggest sphere algorithm. Consequently, the authors required an unphysically high value of 40 to compensate this hidden effect.

In the past decade, the emergence of high-entropy alloys (HEAs) and other high-entropy materials (HEMs) has brought about new opportunities in the development of novel materials for high-performance applications. In combining solid-solution (SS) strengthening with grain-boundary strengthening, new material systems—nanostructured or nanocrystalline (NC) HEAs or HEMs—have been developed, showing superior combined mechanical and functional properties compared with conventional alloys, HEAs, and NC metals. This article reviews the processing methods, materials, mechanical properties, thermal stability, and functional properties of various nanostructured HEMs, particularly NC HEAs. With such new nanostructures and alloy compositions, many interesting phenomena and properties of such NC HEAs have been unveiled, for example, extraordinary microstructural and mechanical thermal stability. As more HEAs or HEMs are being developed, a new avenue of research is to be exploited. The article concludes with perspectives about future directions in this field.

The materials chosen to make thermal engines, spacecrafts, or human implants cannot fail in an unpredictable way to guarantee the users' well-being. These applications can benefit from the use of ceramics because of their temperature resistance, corrosion resistance, or hardness. Although parts based on ceramic matrix composites and zirconia are already in use, a more recent ceramic with a structure inspired from seashells provides an attractive combination of ease of processing, high strength, and high toughness. These nacre-like aluminas are made of aligned micron-sized monocrystalline platelets joined together by a mix of mineral secondary phase and nanoparticles. The review's first objective is to provide a picture of what these newly developed bioinspired ceramics are capable of within today's ceramic and nacre-inspired composites landscape. I will also extract from the results the links between process/microstructure/performance to better understand the potential of these materials in terms of toughness and strength increase. Finally, I will present the challenges that are ahead to eventually reproduce the exceptional fracture behavior observed in nacre.

Uranium–35 wt.% zirconium (U–35 wt.% Zr) alloy was annealed for 1 h and 24 h at 650 °C and characterized to understand the early-stage microstructure evolution. Dendritic microstructure with fine (∼300 nm in length) α-U precipitates clustered between dendrite branches were observed in the 1-h annealed sample. After 24-h annealing at 650 °C, the α-U precipitates coarsened, and the dendritic microstructure disappeared because of microstructure homogenization. Furthermore, microchemical homogenization observed with energy-dispersive X-ray spectroscopy analysis suggests that α-U precipitates are approaching thermodynamic equilibrium in the 24-h annealed sample. The findings from this study have potential impacts on the manufacturing and computer modeling of metallic nuclear fuel.

Concentrated solid-solution alloys (CSAs) demonstrate excellent mechanical properties and promising irradiation resistance depending on their compositions. Existing experimental and simulation results indicate that their heterogeneous structures induced by the random arrangement of different elements are one of the most important reasons responsible for their outstanding properties. Nevertheless, the details of this heterogeneity remain unclear. Specifically, which properties induced by heterogeneity are most relevant to their irradiation response? In this work, we scrutinize the role of heterogeneity in CSAs played in damage evolution in different aspects through atomistic simulations, including lattice misfit, thermodynamic mixing, point defect energetics, point defect diffusion, and dislocation properties. Our results reveal that structural parameters, such as lattice misfit and enthalpy of mixing, are generally not suitable to assess their irradiation response under cascade conditions. Instead, atomic-level defect properties are the keys to understand defect evolution in CSAs. Therefore, tuning chemical disorder to tailor defect properties is a possible way to further improve the irradiation performance of CSAs.

The breakdown of the columnar grains and lamellar α + β colony microstructure in two-phase Ti alloys during conversion of ingot to billet is critical to the development of desired combination of mechanical properties. Colony breakdown occurs during a series of thermomechanical processing steps in the α + β phase field. However, fundamental knowledge of the microstructural dependence of this transformation is limited, particularly its dependence on the initial orientation of the α + β colony relative to the imposed strain-path. In this study, the viscoplastic self-consistent polycrystal plasticity model is used to examine deformation behavior as a function of crystal loading direction. Criteria were developed to predict relative globularization rates; it was found that both slip system activities in the α phase and relative crystal rotations of each phase must be considered. Predictions are demonstrated to be consistent with literature and suggest that further experimental investigation of relative globularization rates is necessary.