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Metallurgy

This collection highlights some of the experimental and theoretical work published in Nature Communications on the science and engineering of load-bearing materials. Explore the latest research on high entropy alloys, bulk metallic glasses, grain boundaries, phase transitions, and crystal growth, and processing, defects, and mechanical properties

High entropy alloys

In dual-phase Cantor-like high entropy alloys, how local chemistry affects enhanced deformation mechanisms remains unclear. Here, the authors image 3D stacking fault networks formation and show they both impede dislocations and facilitate phase transformations via local chemical composition variations.

Article | Open Access | | Nature Communications

Multi-principal-element alloys have been assumed to have the configurational entropy of an ideal solution. Here, the authors use atomistic simulations to show that instead NiCoCr exhibits local chemical order, raising the activation barriers of dislocation activities to elevate mechanical strength.

Article | Open Access | | Nature Communications

The identification of high entropy alloys is challenging given the vastness of the compositional space associated with these systems. Here the authors propose a supervised learning strategy for the efficient screening of high entropy alloys, whose hardness predictions are validated by experiments.

Article | Open Access | | Nature Communications

Medium entropy alloy CoCrNi has better mechanical properties than high entropy alloys such as CrMnFeCoNi, but why that is remains unclear. Here, the authors show that a nanostructured phase at lattice defects in CoCrNi causes its extraordinary properties, while it is magnetically frustrated and suppressed in CrMnFeCoNi.

Article | Open Access | | Nature Communications

Exploration of high entropy alloy phases where little experimental data exists is still challenging. Here, the authors develop an approach where parameters from first principle simulations are incorporated into Monte Carlo simulations to reproduce phase evolution of aluminium-containing high entropy alloys.

Article | Open Access | | Nature Communications

Twinning has been experimentally seen in high-entropy alloys, but understanding how it operates remains a challenge. Here, the authors show that twinning can be a primary deformation mechanism in three well-known medium- and high-entropy alloys that have unstable face-centered cubic lattices.

Article | Open Access | | Nature Communications

Producing in situ composite materials with superior strength and ductility has long been a challenge. Here, the authors use lamellar microstructure inherited from casting, rolling, and annealing to produce an ultrafine duplex eutectic high entropy alloy with outstanding properties.

Article | Open Access | | Nature Communications

Materials that show twinning-induced plasticity can offer unusual combinations of strength and ductility. Here, authors study deformation twinning and dislocation behaviour in a medium-entropy alloy CrCoNi and find a three-dimensional (3D) hierarchical twin network that forms from the activation of three twinning systems.

Article | Open Access | | Nature Communications

CrMnFeCoNi high entropy alloys have high fracture toughness at cryogenic temperatures due to deformation twinning but twinning is not active in this alloy at room temperature. Here authors optimize composition and thermomechanical treatments to introduce non-recrystallized grains, producing high yield strength while maintaining good ductility.

Article | Open Access | | Nature Communications

Whether a polymorphic transition exists in high entropy alloys or not remains unclear since discovery of these alloys more than a decade ago. Here authors report an irreversible polymorphic transition fromfcc to hcp in the prototype FeCoCrMnNi high entropy alloy and provide evidence for fccphase being more stable than hcp phase only at high temperatures.

Article | Open Access | | Nature Communications

High-entropy alloys represent a new strategy for the design of materials with properties superior to those of conventional alloys, but are largely limited to simple phases of cubic symmetry. By applying high pressures on CrMnFeCoNi, here authors demonstrate synthesis of a hexagonal close-packed phase.

Article | Open Access | | Nature Communications

High-entropy alloys derive their properties from being multi-element systems that can crystallize as a single phase. Here, the authors examine a medium-entropy alloy, CrCoNi, which displays strength-toughness properties exceeding those of high-entropy alloys and resulting from steady strain hardening.

Article | Open Access | | Nature Communications

Radiation tolerance is a property determined both by materials structure and defect dynamics. Here authors demonstrate enhancement of radiation tolerance at elevated temperatures in equiatomic single-phase concentrated solid solution alloys and propose an underlying mechanism.

Article | Open Access | | Nature Communications

In high entropy alloys a mix of a large number of five or more principal atomic elements is used to tune the properties. Here, the authors present a solution to the problem of predicting the properties of the huge number of potential alloys by developing an efficient screening approach based on automated calculations.

Article | Open Access | | Nature Communications

Bulk metallic glasses

While metallic glasses are expected to have tunable structures, these have rarely been demonstrated. Here, the authors combine temperature and pressure to show a two-way structural tuning in rare earth-based metallic glasses beyond the nearest-neighbor atomic shells.

Article | Open Access | | Nature Communications

The coarsening of amorphous metallic nanoparticles remains poorly understood. Here, the authors combine high resolution microscopy and atomistic simulations to show the disordered structure of amorphous nanoparticles makes them coarsen faster than crystalline ones.

Article | Open Access | | Nature Communications

Thermal annealing of metallic glasses is known to cause a universal increase of the relaxation time with sample age. Here, however, the authors show how a mechanical stress disrupts this universal response, leading to highly non-monotonous structural dynamics with time.

Article | Open Access | | Nature Communications

Conventional crystal growth models assume crystals grow into a structure-less liquid, even though liquid metals have shown evidence of structural ordering. Here, the authors show crystal growth can be influenced by the presence of thermodynamically unstable local structural order in the liquid.

Article | Open Access | | Nature Communications

Producing ultrastable metallic glasses has always been associated with substrates heated close to the glass transition temperature. Here, the authors show that reducing the deposition rate of the metallic glass on a cold substrate produces ultrastable metallic glasses with remarkably improved stability.

Article | Open Access | | Nature Communications

Directly relating the mechanical properties of metallic glasses to their atomic structure remains a challenge. Here, the authors use high resolution microscopy to show many mechanical properties of metallic glasses depend on a single structural parameter, the characteristic length of spatial heterogeneity.

Article | Open Access | | Nature Communications

Deforming metallic glasses can rejuvenate them to higher energy states, but only in the shear bands where deformation is usually concentrated. Here, the authors use a notched setup to suppress shear banding and promote significant bulk softening of a zirconium-based metallic glass.

Article | Open Access | | Nature Communications

An anomalous exothermal calorimetric peak far below crystallization temperatures in prototypical Pd-Ni-P glasses has been recognized for four decades. Here authors use neutron and high-energy X-ray diffraction to find evidence for a polyamorphous phase transition where medium-range order undergoes large changes while short-range order changes little.

Article | Open Access | | Nature Communications

The crystal formation waiting time of a homogeneous supercooled liquid exhibits a pronounced minimum depending on temperature, and this minimum is a measure of glass forming ability. Here, the authors propose an expression for this minimum for all metallic glasses that depends only on two fitting parameters.

Article | Open Access | | Nature Communications

The atomic structure of metallic glasses is related to their properties such as the ability of materials to form glasses. Here, the authors develop a new approach to model the atomic structure of metallic glasses, to enable a better connection between atomic structure and glass properties.

Article | Open Access | | Nature Communications

Phases and phase transitions

Aluminium alloys can naturally age and form microstructural clusters that affect their mechanical properties. Here, the authors show that nanosized samples do not under undergo natural aging because diffusion-controlled clustering processes are inhibited.

Article | Open Access | | Nature Communications

Imaging deformation twins in three dimensions is difficult and they are usually viewed as two-dimensional ellipsoids. Here, the authors statistically analyze more than two hundred deformation twins in magnesium observed in three different views and show lateral twin expansion is faster than forward propagation.

Article | Open Access | | Nature Communications

Commercial alloys contain trace solutes that segregate at grain boundaries but have been difficult to directly image due to electron beam damage. Here, the authors use atomic-resolution energy dispersive X-ray spectroscopy at lower electron voltage to image segregation at magnesium alloy twin boundaries.

Article | Open Access | | Nature Communications

Little is known about diffusion along metal/ceramic interfaces even though it controls the physical behavior and lifetimes of many devices (including batteries, microelectronics, and jet engines). Here, the authors show that diffusion along a nickel/sapphire interface is abnormally fast due to nickel vacancies and generalise their findings to a wide-range of metal/ceramic systems.

Article | Open Access | | Nature Communications

Classifying crystal structures using their space group is important to understand material properties, but the process currently requires user input. Here, the authors use machine learning to automatically classify more than 100,000 simulated perfect and defective crystal structures.

Article | Open Access | | Nature Communications

Exactly how hydrogen renders metals brittle is still unclear, and it remains a challenge to predict component failure due to hydrogen embrittlement. Here, the authors identify a class of grain boundaries in a nickel superalloy that deflects propagating cracks and improves alloy resistance to hydrogen.

Article | Open Access | | Nature Communications

Sulfur at nickel grain boundaries can cause catastrophic failure, but the mechanisms behind that embrittlement remain poorly understood. Here, the authors image and model bipolar sulfur–nickel structures at amorphous-like and bilayer-like facets of general grain boundaries that cause embrittlement.

Article | Open Access | | Nature Communications

Displacive martensitic transformations through lattice distortion usually involve a change from one crystal structure to another. Here however, the authors “melt” metastable Ti alloys during cooling and show that a martensitic transformation can lead to the formation of an intragranular amorphous phase.

Article | Open Access | | Nature Communications

The atomic structure of grain boundary phases remains unknown and is difficult to investigate experimentally. Here, the authors use an evolutionary algorithm to computationally explore interface structures in higher dimensions and predict low-energy configurations, showing interface phases may be ubiquitous.

Article | Open Access | | Nature Communications

Understanding how individual crystals share load inside a polycrystal is crucial to improve component lifetime, but remains difficult to measure. Here, the authors show that the crystal orientation of a grain and that of its neighbours can surprisingly cause stress relaxation in zirconium and titanium under load.

Article | Open Access | | Nature Communications

Conventional grain growth models assume the velocity of a grain boundary is proportional to its curvature but cannot account for the many deviations observed experimentally. Here, the authors present a model that connects grain growth directly to the disconnection mechanism of grain boundary migration and can account for these deviations.

Article | Open Access | | Nature Communications

Coherent twin boundaries (CTBs) in face-centered cubic metals are usually considered unable to slide at room temperature. Here, the authors use in situ transmission electron microscopy and molecular dynamics to show CTB sliding in copper nanopillars when leading and trailing partial dislocations have similar Schmid factors.

Article | Open Access | | Nature Communications

One way of tuning mechanical properties of alloys lies in utilizing athermal phase transitions. Here authors report a complexion-mediated martensitic transformation in Ti alloys yielding a nanolaminate structure of martensite bounded by planar complexions, promising new strategies for the design of high strength Ti alloys.

Article | Open Access | | Nature Communications

In magnetic shape memory Heusler alloys, the premartensite phase is believed to be a precursor state of the martensite phase with preserved austenite phase symmetry. Here, the authors show that the premartensite is a stable phase with its own crystallographic symmetry resulting from the stepped growth of Bain distortions in the lattice.

Article | Open Access | | Nature Communications

Solid–solid phase transition via an intermediate liquid state has been identified in colloidal systems, but the universality of the phenomenon at atomic scales has not yet been proved. Pogatscher et al.observe a similar transition in a metallic glass system using fast differential scanning calorimetry.

Article | Open Access | | Nature Communications

Defects and mechanical properties

Adding minute amounts of rhenium to Ni-based single crystal superalloys extends their high temperature performance in engines, but the reasons behind that are still unclear. Here, the authors combine high resolution imaging and modelling to show that rhenium enriches and slows down partial dislocations to improve creep performance.

Article | Open Access | | Nature Communications

Understanding the interactions between solute atoms and crystalline defects is essential for determining alloy properties. Here the authors use a linear regression model to propose a quantitative correlation between local electronic structure descriptors and the solute-defect interaction energies in bcc refractory alloys.

Article | Open Access | | Nature Communications

Incorporating and dispersing dense nanoparticles into metals remains a challenge. Here, the authors use nanocomposite powders containing very dense nanoparticles to print an aluminium nanocomposite with one of the highest specific modulus and yield strength among all structural materials.

Article | Open Access | | Nature Communications

Understanding fast phenomena that happen in hot and opaque environments, such as during metal foaming, remains a challenge. Here, the authors use ultra-fast imaging of more than 200 three-dimensional volumes per second to explore bubble coalescence in an aluminium alloy.

Article | Open Access | | Nature Communications

3D printing pore-free complex metal parts remains a challenge. Here, the authors combine in-situ imaging and simulations to show thermocapillary force can eliminate pores from the melt pool during a laser powder bed fusion process.

Article | Open Access | | Nature Communications

Inkfree multi-material printing is a common challenge in 3D printing. Here, the authors introduce electrohydrodynamic redox printing, a method that enables the deposition of multiple metals and their alloys with nanoscale resolution and thus the synthesis of materials with locally tuned properties.

Article | Open Access | | Nature Communications

Hydrogen contamination in metals during sample preparation for high-resolution microscopy remains a challenge, especially when hydrogen itself is being investigated. Here, the authors show that using cryogenic milling significantly reduces hydrogen pick-up during sample preparation of titanium and titanium alloys.

Article | Open Access | | Nature Communications

3D printing of titanium alloys today is based on known alloy compositions that result in anisotropic structural properties. Here, the authors add lanthanum to commercially pure titanium and exploit a solidification path that reduces texture and anisotropy.

Article | Open Access | | Nature Communications

Solution treatment and quenching can strengthen magnesium-lithium-aluminium alloys, but this strength decreases with ageing. Here, the authors show this is due to semi-coherent nanoparticle precipitation followed by coarsening, and control the lattice mismatch to stabilise the microstructure.

Article | Open Access | | Nature Communications

Detrimental serrated plastic flow via dynamic strain aging (DSA) in conventionally processed nickel superalloys usually occurs during high temperature deformation. Here, the authors suppress DSA via a unique microstructure obtained using additive manufacturing and propose a new dislocation-arrest model in nickel superalloys.

Article | Open Access | | Nature Communications

Metals deformed at very high rates experience a rapid increase in flow stress due to dislocation drag. Here, the authors stabilise a nanocrystalline microstructure to suppress dislocation velocity and limit drag effects, conserving low strain-rate deformation mechanisms up to higher strain rates and temperatures.

Article | Open Access | | Nature Communications

While metallic nanosized objects are stronger than their macroscopic counterparts, they rarely reach the metal’s maximum theoretical strength. Here, the authors produce faceted nickel nanoparticles and show that their strength under compression matches the theoretically predicted strength in the literature.

Article | Open Access | | Nature Communications

Identifying atomic defects during deformation is crucial to understand material response but remains challenging in three dimensions. Here, the authors couple X-ray Bragg coherent diffraction imaging and atomistic simulations to correlate a strain field to a screw dislocation in a single copper grain.

Article | Open Access | | Nature Communications

Quasicrystal precipitation in alloys should be favored at dislocations, which break crystal symmetry, but almost all precipitates at dislocations are periodic. Here, the authors show rare quasicrystal formation along dislocations in a magnesium zinc alloy with atomic resolution.

Article | Open Access | | Nature Communications

Most current methods for additive manufacturing of complex metallic 3D structures are limited to a resolution of 20–50 µm. Here, the authors developed a lithography-based process to produce 3D nanoporous nickel nanolattices with octet geometries and a resolution of 100 nm.

Article | Open Access | | Nature Communications

Twin nucleation in face-centered cubic metals with high twin-fault energies should theoretically be unfavourable, but instead twinning is very often observed. Here, the authors report a new twinning route in nanocrystalline platinum that bypasses the high twin-fault energy barrier using closely spaced partial dislocations.

Article | Open Access | | Nature Communications

Research in new alloy compositions and treatments may allow the increased strength of mass-produced, intricately shaped parts. Here authors introduce a superplastic medium manganese steel which has an inexpensive lean chemical composition and which is suited for conventional manufacturing processes.

Article | Open Access | | Nature Communications

Replacing steel or aluminium vehicle parts with magnesium would result in reduced emissions, but shaping magnesium without cracking remains challenging. Here, the authors successfully extrude and roll textured magnesium into ductile foil at low temperatures by activating intra-granular mechanisms.

Article | Open Access | | Nature Communications

Growing large single crystals cheaply and reliably for structural applications remains challenging. Here, the authors combine accelerated abnormal grain growth and cyclic heat treatments to grow a superelastic shape memory alloy single crystal to 70 cm.

Article | Open Access | | Nature Communications

Nanocrystalline metals often exhibit high strength yet suffer from poor ductility. Here, the authors employ grain boundary engineering to overcome this problem by introducing amorphous intergranular films, which enables superior mechanical properties in copper-zirconium alloys.

Article | Open Access | | Nature Communications

Due to its high diffusivity, hydrogen is considered a weak inhibitor or even a promoter of dislocation movements in metals and alloys. Here the authors quantitatively demonstrate that after exposing aluminium to hydrogen, mobile dislocations can lose mobility, due to segregation of hydrogenated vacancies to dislocations.

Article | Open Access | | Nature Communications