Multiple origins of extra electron diffractions in fcc metals.

Diffuse intensities in the electron diffraction patterns of concentrated face-centered cubic solid solutions have been widely attributed to chemical short-range order, although this connection has been recently questioned. This article explores the many nonordering origins of commonly reported features using a combination of experimental electron microscopy and multislice diffraction simulations, which suggest that diffuse intensities largely represent thermal and static displacement scattering. A number of observations may reflect additional contributions from planar defects, surface terminations incommensurate with bulk periodicity, or weaker dynamical effects.

Kink bands promote exceptional fracture resistance in a NbTaTiHf refractory medium-entropy alloy.

Single-phase body-centered cubic (bcc) refractory medium- or high-entropy alloys can retain compressive strength at elevated temperatures but suffer from extremely low tensile ductility and fracture toughness. We examined the strength and fracture toughness of a bcc refractory alloy, NbTaTiHf, from 77 to 1473 kelvin. This alloy's behavior differed from that of comparable systems by having fracture toughness over 253 MPa·m, which we attribute to a dynamic competition between screw and edge dislocations in controlling the plasticity at a crack tip.

Exceptional fracture toughness of CrCoNi-based medium- and high-entropy alloys at 20 kelvin.

CrCoNi-based medium- and high-entropy alloys display outstanding damage tolerance, especially at cryogenic temperatures. In this study, we examined the fracture toughness values of the equiatomic CrCoNi and CrMnFeCoNi alloys at 20 kelvin (K). We found exceptionally high crack-initiation fracture toughnesses of 262 and 459 megapascal-meters (MPa·m) for CrMnFeCoNi and CrCoNi, respectively; CrCoNi displayed a crack-growth toughness exceeding 540 MPa·m after 2.

Magnetically driven short-range order can explain anomalous measurements in CrCoNi.

The presence, nature, and impact of chemical short-range order in the multi-principal element alloy CrCoNi are all topics of current interest and debate. First-principles calculations reveal that its origins are fundamentally magnetic, involving repulsion between like-spin Co-Cr and Cr-Cr pairs that is complemented by the formation of a magnetically aligned sublattice of second-nearest-neighbor Cr atoms. Ordering models following these principles are found to predict otherwise anomalous experimental measurements concerning both magnetization and atomic volumes across a range of compositions.

On the Origins of Fracture Toughness in Advanced Teleosts: How the Swordfish Sword's Bone Structure and Composition Allow for Slashing under Water to Kill or Stun Prey.

The osseous sword of a swordfish () is specialized to incapacitate prey with stunning blows. Considering the sword's growth and maturation pattern, aging from the sword's base to the tip, while missing a mechanosensitive osteocytic network, an in-depth understanding of its mechanical properties and bone quality is lacking. Microstructural, compositional, and nanomechanical characteristics of the bone along the sword are investigated to reveal structural mechanisms accounting for its exceptional mechanical competence.

Osteocyte-Intrinsic TGF-β Signaling Regulates Bone Quality through Perilacunar/Canalicular Remodeling.

Poor bone quality contributes to bone fragility in diabetes, aging, and osteogenesis imperfecta. However, the mechanisms controlling bone quality are not well understood, contributing to the current lack of strategies to diagnose or treat bone quality deficits. Transforming growth factor beta (TGF-β) signaling is a crucial mechanism known to regulate the material quality of bone, but its cellular target in this regulation is unknown.

Bioinspired Hydroxyapatite/Poly(methyl methacrylate) Composite with a Nacre-Mimetic Architecture by a Bidirectional Freezing Method.

Using a bidirectional freezing technique, combined with uniaxial pressing and in situ polymerization, "nacre-mimetic" hydroxyapatite/poly(methyl methacrylate) (PMMA) composites are developed by processing large-scale aligned lamellar ceramic scaffolds. Structural and mechanical characterization shows "brick-and-mortar" structures, akin to nacre, with interesting combinations of strength, stiffness, and work of fracture, which provide a pathway to making strong and tough lightweight materials.