Muscle is a hierarchical composite material, and that architecture is the key to the new framework. At the smallest level sit myofibrils, the contractile protein threads built from repeating sarcomeres, each containing Z-disks, A-bands, and H-bands. Myofibrils bundle together into muscle fibers, wrapped in a thin collagenous sheath called the endomysium. Fibers in turn group into bundles encased in a thicker connective tissue layer, the perimysium. Connective tissues form a continuous network that reinforces the muscle and transmits force between fibers and bundles. Because each level contributes to the whole, the team hypothesized that macroscopic texture could be quantitatively predicted if the mechanical properties of the microscopic components and their volume fractions were known.

Testing that hypothesis required measuring mechanics at scales where no conventional test can operate. The researchers turned to atomic force microscopy, or AFM, a technique in which an ultrasharp silicon nitride tip, with a radius of just a few nanometers, is pressed against a sample while the force of contact is recorded. Fitting the resulting force-indentation curves with the Derjaguin-Muller-Toporov contact model, which accounts for both elastic deformation and van der Waals adhesion, yields the local Young’s modulus. The team applied this to myofibrils isolated from pork tenderloin, beef tenderloin, and chicken breast, as well as to extracted endomysium and perimysium, measuring both dried and hydrated samples. Hydration mattered enormously: dried myofibrils showed moduli in the gigapascal range, while wet samples dropped by one to two orders of magnitude into the tens of megapascals, a reminder that data from dried biological materials can have limited relevance to real food.

The nanoscale maps revealed striking patterns. In raw myofibrils, stiffness followed a consistent spatial order across all three species: the Z-disk was stiffest, the A-band intermediate, and the H-band softest, echoing earlier AFM studies on rabbit and rat muscle. Species differences were also clear. In the hydrated raw state, pork myofibrils were the stiffest at roughly 50 megapascals, beef followed at about 47, and chicken was softest at around 34. Cooking reshuffled the dried-state landscape, erasing the species-specific sarcomere structures as proteins denatured and aggregated, but the wet cooked myofibrils preserved the same hierarchy, with pork highest at about 75 megapascals and chicken lowest at about 45. The collagenous membranes told their own story: the perimysium was consistently slightly stiffer than the endomysium, and both stiffened after cooking, likely through heat-induced collagen denaturation and aggregation.

With the microscopic inputs in hand, the team built a two-level analytical model based on the classical Reuss series scheme from composite mechanics. Under transverse compression, a single muscle fiber was treated as myofibrils embedded in an endomysium matrix, and a fiber bundle as equivalent fibers in series with the perimysium. The effective modulus of each level is the volume-fraction-weighted combination of its phases, with the phase fractions measured from scanning electron microscope images of fiber cross-sections. Running the numbers, the model predicted bundle moduli that ranked pork highest, beef intermediate, and chicken lowest, and predicted a significant increase after cooking, trends that mirror the myofibril data feeding into it. Notably, the predicted bundle modulus correlated strongly with the myofibril and endomysium moduli but not with the perimysium modulus, suggesting that in this low-connective-tissue muscle system, the bundle stiffness is governed primarily by the fibers themselves.

The validation step came from macroscopic compression tests on cubes of raw and cooked meat using a texture analyzer, with the compression axis carefully aligned perpendicular to the muscle fibers to match the orientation of the nanoscale measurements. The stress-strain curves were strongly nonlinear, stiffening as strain increased, so the team fitted them with two constitutive models. A combined logarithmic-polynomial hyperelastic model, originally developed for liver tissue, captured the general shape but showed systematic deviations, particularly for chicken. A logistic model, adapted from work on passive spinal muscle mechanics, performed far better, with coefficients of determination above 0.997 for every sample. Its parameters carried clear physical meaning: an initial modulus reflecting the relaxed response of the microscopic components, a hardening increment describing nonlinear stiffening, a hardening rate, and a critical strain at which stiffening accelerates.

The correlation analysis tied the scales together. The logistic model’s initial modulus correlated strongly with the linear modulus measured from the first five percent of strain, and both correlated with the multiscale model’s predicted bundle modulus and, through it, with the myofibril and endomysium properties. In other words, the initial stiffness of a piece of meat is largely written into its myofibrils. The nonlinear parameters told a different story. Beef showed the largest hardening increment, which the authors attribute to its denser network of mature collagen crosslinks and the pronounced nonlinear hardening behavior of the perimysium observed in the AFM force curves, potentially explaining why beef is chewier than pork or chicken. Bound water content correlated positively with the initial stiffness parameters, while free water correlated negatively with the hardening rate, hinting that water acts as a lubricant that smooths the structural response under compression.

The authors are careful about scope. The AFM-derived moduli of the isolated connective tissues represent effective properties of collagen-rich fractions rather than absolute in situ values, and the constitutive models describe rate-independent behavior at a single loading speed rather than the full viscoelastic response of muscle. Validation was performed on three relatively lean, low-connective-tissue muscles, so extending the framework to collagen-rich cuts such as tendon-laden muscles remains future work. The link between micro- and macroscale is also framed as a parametric correlation rather than a direct numerical equivalence, with microscopic stiffness serving as the physical foundation for macroscopic structural stiffness rather than substituting for it one-to-one.

Even with those caveats, the implications are broad. The study delivers a quantitative, bottom-up route from nanoscale protein mechanics to the texture a consumer actually perceives, clarifying which hierarchical structures dominate which aspects of the mechanical response. For the booming plant-based meat industry, where replicating the fibrous architecture and anisotropic mechanics of real muscle remains the central challenge, the framework offers something like a design blueprint: a way to specify the stiffness and volume fraction of the protein and matrix phases needed to hit a target bite. More broadly, it demonstrates that with enough care at the nanoscale, even something as familiar and complex as the texture of dinner can be reduced to physics you can measure, model, and ultimately engineer.

Subject of Research: Multiscale mechanical modeling linking AFM nanomechanics of myofibrils and connective tissue to the macroscopic compressive texture of meat

Article Title: Predicting the compression mechanical properties of muscle from microscale indentation mechanics using multiscale mechanical models

Article References: Zhao, C., Jiang, R., Zhang, Z., Jia, J., Nishinari, K., & Yang, N. (2026). Predicting the compression mechanical properties of muscle from microscale indentation mechanics using multiscale mechanical models. Current Research in Food Science, Article 101577. https://doi.org/10.1016/j.crfs.2026.101577

Image Credits: AI Generated

DOI: 10.1016/j.crfs.2026.101577

Keywords: meat texture, atomic force microscopy, myofibrils, multiscale modeling, connective tissue, food science, compression mechanics, plant-based meat, collagen, constitutive models, Reuss model, nanoindentation

The technique at the heart of the study is diffusion bonding, a solid-state joining process in which two polished metal surfaces are pressed together under a modest load of roughly 70 kilopascals and heated to 900 degrees Celsius, well below the melting point of either metal, for four hours inside a vacuum furnace. At that temperature, atoms begin to migrate across the boundary between the two plates, weaving a metallurgical bond without ever liquefying the materials. The specimens, cut from sheets of the workhorse titanium alloy Ti-6Al-4V and pure vanadium, were then rapidly cooled in a helium quench, locking in whatever microstructures and internal stresses the bonding process had created. The team chose bonding parameters of 900 degrees for four hours after testing a range of temperatures and times, because this window produced an interface free of delamination, with minimal pores and a broad transition zone ideal for analysis.

Why vanadium? The choice is far from arbitrary. Vanadium is one of the very few elements that forms solid solution alloys with both titanium and iron across wide composition ranges, which means it suppresses the formation of brittle intermetallic compounds that plague direct titanium-to-steel joints. Those intermetallic phases are the classic villains of dissimilar metal joining: they create hard, brittle regions that crack and delaminate under load. The long-term goal of the research program is to bond titanium directly to stainless steel, and vanadium is being evaluated as an interlayer, a metallurgical diplomat that stands between two metals that would otherwise wage war on each other’s crystal structures. Understanding the titanium-vanadium interface is therefore the essential first step toward a much more ambitious joining technology.

Using electron backscatter diffraction and energy dispersive spectroscopy, the researchers discovered that the interface is not a sharp line but a layered landscape of four distinct microstructural regions. On the titanium side sit the fine primary alpha-titanium grains, averaging about 10.6 micrometers, arranged in the banded texture typical of rolled sheet. Moving toward the vanadium, they found a thin transformation structure of alpha-titanium laths, then a broad zone of large body-centered cubic beta-titanium grains, and finally the coarse vanadium grains, roughly three times larger than their titanium counterparts at about 31.3 micrometers. Energy dispersive spectroscopy line scans traced the compositional gradients across these zones, showing titanium and aluminum concentrations gradually declining and then dropping abruptly to zero at the edge of the beta-titanium region, while vanadium showed the mirror-image trend.

The beta-titanium zone is the star of the show, and its existence tells a subtle metallurgical story. Vanadium is a beta-stabilizer, an element that lowers the temperature at which titanium’s crystal structure transforms and allows the high-temperature beta phase to survive at room temperature. As vanadium atoms diffused into the titanium alloy during bonding, they stabilized a layer of beta-titanium grains that were retained during cooling. A parent grain reconstruction, a computational technique that mathematically reverts the low-temperature microstructure back to its high-temperature ancestor, revealed that the alpha-titanium transformation structure nucleated directly from these retained beta grains rather than from the primary alpha-titanium. The transformation structure thus marks the approximate frontier where vanadium diffusion ran out of steam, a fossil record of the bonding process frozen in crystal structure.

Crucially, the energy dispersive spectroscopy results confirmed that no brittle intermetallic phases formed anywhere along the interface, exactly the outcome the vanadium interlayer strategy is designed to achieve. Only a scattering of small pores appeared in select areas. This is a genuine victory for the multi-material joining community, because it demonstrates that a titanium alloy and a refractory metal can be joined cleanly through solid-state diffusion, setting the stage for titanium-to-steel joints that would be impossible without such a buffer.

But a clean bond is only half the story. Advanced manufacturing methods that join dissimilar metals inevitably leave behind residual stresses, internal forces locked into the material that can cause geometric distortion or outright part failure over time. These stresses arise from several sources: the mismatch between body-centered cubic and hexagonal crystal structures, differences in thermal expansion between the joined materials, dislocations piling up at the interface, and the lattice strain caused by vanadium atoms, which are slightly smaller than titanium atoms, squeezing into substitutional positions in the titanium matrix. Measuring these hidden forces, however, turns out to be nearly as difficult as creating the bond in the first place.

The team attacked the problem with three complementary techniques. Cross-correlation electron backscatter diffraction compares diffraction patterns from within individual grains against a reference pattern chosen as the least strained in each grain, detecting pattern shifts with a sensitivity of about one part in ten thousand to map local elastic strains and stresses. Nanoindentation, using a Berkovich tip pressed into the sample two hundred times across the interface, estimated stresses from how hardness changes under load, following the Suresh-Giannakopoulos methodology. Finally, X-ray diffraction with the sin-squared-psi method averaged stress over a larger beam footprint on the sample surface. The results painted a nuanced picture: the beta-titanium region showed the highest stresses, with nanoindentation yielding average tensile values of about 522 megapascals there and 265 megapascals in vanadium, while X-ray diffraction found tensile stresses of roughly 96 to 241 megapascals in the titanium region and no significant stress in vanadium. Kernel average misorientation maps independently confirmed that lattice curvature, a proxy for dislocation density and plastic strain, was highest around the alpha-titanium transformation structure and at the beta-titanium-vanadium boundaries.

Yet the study’s most instructive finding may be about the measurement techniques themselves. The nanoindentation results in the fine-grained primary alpha-titanium region produced stress values far above the alloy’s yield strength, numbers the authors frankly describe as not feasible. The culprits are instructive: the tiny titanium grains mean indents often landed on or near grain boundaries, small amounts of beta phase mixed into the alpha region meant some indents were compared against the wrong reference material, and the method’s dependence on a stress-free reference becomes treacherous across a compositional gradient. The beta-titanium phase posed a particular dilemma, since it is metastable and its composition varies across the interface, making a true stress-free reference specimen nearly impossible to create experimentally. The authors suggest that computational methods could supply theoretical references at each measurement point, a hybrid experimental-computational approach that may become standard practice.

The implications ripple outward across aerospace, automotive, and medical engineering, where dissimilar metal joints promise weight savings, cost reduction, and design flexibility that single-material parts cannot match. This work demonstrates that vanadium can broker a clean, intermetallic-free union between titanium and a future steel partner, while also delivering a candid assessment of how compositional gradients complicate quantitative stress analysis. As multi-material manufacturing accelerates, from additively manufactured functionally graded components to hybrid aerospace structures, the ability to predict and measure the invisible stresses lurking at dissimilar metal interfaces will determine whether these ambitious parts fly, drive, and heal safely. The titanium-vanadium seam, once an obscure metallurgical curiosity, is now a well-lit window into that future.

Subject of Research: Microstructure and residual stress characterization at a diffusion bonded vanadium to Ti-6Al-4V interface

Article Title: Microstructure and residual stress at diffusion bonded interface between vanadium and Ti-6Al-4V

Article References: Adams, C. L., Gaskey, B., Wilkins, M. C. D., Carpenter, J., & Field, D. P. (2026). Microstructure and residual stress at diffusion bonded interface between vanadium and Ti-6Al-4V. Journal of Materials Science: Metallurgy, 1(1), Article 4. https://doi.org/10.1007/s44492-026-00005-1

Image Credits: AI Generated

DOI: 10.1007/s44492-026-00005-1

Keywords: diffusion bonding, dissimilar metal joining, Ti-6Al-4V, vanadium, residual stress, electron backscatter diffraction, nanoindentation, X-ray diffraction, beta-titanium, intermetallic phases, microstructure, aerospace materials

The appeal is obvious. Commercial multiwell plates are inexpensive enough at small scale, but custom formats, unusual geometries, and specialized fixtures for microscopy or mechanical testing are either unavailable or prohibitively costly. As 3D printers have proliferated in wet laboratories, researchers have increasingly printed jigs, holders, and even culture chambers on demand. The catch is that a printed object is not automatically a culture device. It must survive sterilization, remain mechanically stable, and, crucially, prove non-toxic to living cells. Those three requirements, the new work shows, do not always travel together.

The team, led by Sergio Noé and Núria Gavara of the Universitat de Barcelona with collaborators at the Universitat Politècnica de Catalunya-BarcelonaTech, focused on two of the most common 3D printing materials: Poly-Lactic Acid (PLA) filament, the workhorse of fused filament fabrication, and Acrylonitrile Butadiene Styrene (ABS)-like photopolymer resins used in vat photopolymerization. Specimens printed from each material were subjected to the three sterilization methods most familiar to cell biologists: ultraviolet light exposure, immersion in ethanol, and steam autoclaving. The researchers then interrogated the treated samples at both macroscopic and nanoscopic scales, using tensile testing to measure bulk mechanical behavior and nanoindentation to probe local stiffness and surface integrity.

The results revealed a striking material-specific pattern of vulnerability. ABS-like resin, which measured 0.31 ± 0.07 GPa in stiffness in its baseline state, remained mechanically viable after UV illumination, which actually raised its measured modulus to 1.19 ± 0.02 GPa, and after autoclaving, at 0.36 ± 0.05 GPa. Ethanol, however, proved catastrophic: submerged specimens deteriorated to a modulus of just 0.01 ± 0.00 GPa, effectively losing their structural integrity. For a material that otherwise tolerates heat and radiation, this solvent sensitivity is a decisive limitation, since ethanol immersion is one of the simplest and most ubiquitous sterilization methods in any laboratory.

Mechanical survival, however, turned out to be only half of the story. Even when ABS-printed devices were successfully sterilized by methods they could tolerate, they proved toxic to cultured cells. Switching to Formlabs Grey resin, an inert photopolymer, did not rescue the situation; the cytotoxic effect persisted. This finding carries a cautionary message for the growing community of laboratory makers: a printed device can pass every mechanical test and still quietly kill the cells it is meant to house. Residual monomers, unreacted photoinitiators, or surface chemistry introduced during printing and post-processing may leach into culture medium in ways that standard material characterization does not detect.

PLA told a different story. Untreated PLA specimens measured 1.22 ± 0.09 GPa and remained essentially unchanged after ethanol immersion, at 1.23 ± 0.15 GPa, and after UV exposure, at 1.21 ± 0.01 GPa. The autoclave, however, was its undoing: steam sterilization dropped the modulus to 0.75 ± 0.20 GPa, a substantial degradation consistent with the hydrolytic and thermal sensitivity of PLA at autoclave temperatures. Here the researchers found an elegant workaround. By switching to Heat-Treated PLA, or HTPLA, a filament that has been thermally annealed to improve its thermal and dimensional stability, the autoclave problem disappeared. HTPLA specimens retained a stiffness of 1.07 ± 0.13 GPa after autoclaving, remaining well within the range compatible with structural use in a culture device.

With a material that could survive the full sterilization arsenal in hand, the team assembled complete glass-bottomed multiwell devices and subjected them to a sequential sterilization protocol combining autoclaving, ethanol treatment, and UV illumination. The resulting platforms were then validated in the most direct way possible: by growing cells on them. Using A549 human lung epithelial cells, the researchers confirmed that the sterilized HTPLA devices supported healthy long-term culture. Cell morphologies appeared normal, and the cells proliferated with a doubling time of 21.06 ± 4.66 hours, a figure consistent with expectations for this cell line in standard culture vessels. The devices also proved compatible with immunostaining workflows, extending their utility beyond simple culture to fixed-cell imaging and molecular labeling experiments.

The combination of a glass optical bottom with a printed polymer body is central to the design’s value. Glass remains the gold standard surface for high-resolution microscopy, offering optical clarity, low autofluorescence, and well-characterized cell adhesion properties that many printed polymers cannot match. By bonding standard glass coverslips into printed well frames, the researchers created devices that behave optically like commercial glass-bottom dishes while retaining the geometric freedom of additive manufacturing. Laboratories can now print multiwells with custom well counts, spacings, or integrated features tailored to specific microscopes, assays, or experiments, and sterilize them with equipment already present in the facility.

The broader significance of the work lies in its systematic approach. Rather than assuming that any sterilization method will suit any printing material, the study provides quantitative mechanical data across a matrix of material-sterilization combinations, exposing failure modes that would otherwise be discovered the hard way, through warped devices, failed cultures, or unexplained cell death. It also demonstrates that the sterilization protocols already standard in cell biology laboratories, UV light, ethanol, and autoclaving, can be applied directly to 3D-printed materials when the material is chosen wisely. The authors frame their contribution as a set of open designs and protocols: in-house 3D-printing and assembly instructions for glass-bottomed multiwells based on HTPLA, paired with optimized sterilization sequences validated for long-term culture and immunostaining.

For laboratories weighing the cost of specialized culture formats, the message is empowering but disciplined. A few hundred euros of printer and filament can replace custom-machined or commercially unavailable devices, but only if researchers respect the material science underneath. Ethanol will destroy ABS-like resins; the autoclave will weaken standard PLA; and even a mechanically sound, sterilized resin print may still poison cells. Heat-treated PLA, processed through a deliberate sequence of autoclave, ethanol, and UV sterilization, currently offers the most reliable path from the printer bed to the incubator. As 3D printing continues its march into wet laboratories, studies like this one supply the evidence base that turns a promising workshop trick into dependable laboratory practice, allowing researchers to print, sterilize, and culture with confidence that their custom devices will protect, not compromise, the cells within.

Subject of Research: Design and sterilization of 3D-printed glass-bottomed multiwell devices for cell culture and immunostaining

Article Title: Design and sterilization of 3D-printed glass-bottomed multiwells for cell culture and immunostaining

Article References: Noé, S., Barberá-Flichi, F., Sanz-Fraile, H., Padilla, J. A., Jorba, I., Buj-Corral, I., Xuriguera, E., Jiménez-Piqué, E., & Gavara, N. (2026). Design and sterilization of 3D-printed glass-bottomed multiwells for cell culture and immunostaining. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-14032-4

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14032-4

Keywords: 3D printing, cell culture, sterilization, HTPLA, PLA, ABS-like resin, glass-bottomed multiwells, immunostaining, additive manufacturing, biomaterials, nanoindentation, autoclaving

High-entropy alloys are unusual materials made by blending several principal elements in near-equal proportions, which boosts configurational entropy, suppresses brittle intermetallic phases, and confers remarkable combinations of strength and toughness. The CrMnFeCoNi alloy, often called the Cantor alloy, is the archetype of the class. Conventionally, such alloys are produced by melting and casting, or by powder metallurgy routes such as spark plasma sintering and hot pressing, which require elevated temperatures. Those thermal steps frequently cause grain coarsening, oxidation, and elemental segregation, degrading the fine microstructures that give nanostructured metals their exceptional properties.

In the new work, the team pre-compacted gas-atomized CrMnFeCoNi powder, with particles ranging from 15 to 53 micrometers, into a small pellet and then subjected it to HPT at a rotation speed of one revolution per minute. Density measurements with helium pycnometry revealed a dramatic jump: the pre-compacted pellet was only 81.6 percent dense, but after a single HPT turn the compacted disk reached about 99.5 percent of the theoretical density of 7.964 grams per cubic centimeter, edging up to 99.7 percent by 15 turns. The sheer intensity of plastic shear between individual powder particles drives this near-complete consolidation without any added heat.

Transmission electron microscopy showed a fully consolidated microstructure free of visible pores, with equiaxed grains of about 30 nanometers at both the disk center and its edge, comparable to the finest grain sizes achieved by HPT processing of cast Cantor alloy. Elemental mapping confirmed that the alloy remained a single face-centered cubic phase. However, the analysis also revealed subtle chemical heterogeneities: thin, elongated bands enriched in chromium, cobalt, and nickel persisted at the disk center, remnants of compositional variations in the original powder particles. At the disk edge, where the accumulated shear strain reaches roughly 600, those inhomogeneities had been dissolved or fragmented into a uniform solid solution, demonstrating how intense shear homogenizes the material.

Not everything survived the processing unscathed. An oxide phase, the spinel compound MnCr2O4, was detected at the disk edge, larger than 200 nanometers, reflecting the oxygen and nitrogen picked up during powder atomization. Manganese and chromium readily form oxides in this alloy system. Still, outside these contamination regions, the compositional analysis showed near-equiatomic distributions of all five metals, underscoring that the room-temperature route preserves chemical integrity to a remarkable degree.

Mechanical testing painted an equally striking picture. Vickers microhardness measurements across the disk diameter rose with processing turns and saturated at 507 plus-or-minus 5, above 500, in a homogeneous distribution, in close agreement with the 510 to 520 hardness values reported for the same alloy when cast and then HPT-processed. Nanoindentation with a Berkovich diamond tip at strain rates from 1.25 times ten to the minus four to one times ten to the minus three per second captured the flow behavior in detail. Early-stage compacts, after one or two turns, showed wider scatter in load-displacement curves, revealing residual microstructural inhomogeneity that disappeared by 15 turns.

One of the most consequential findings concerns temperature. Friction between powders and internal friction in the consolidating bulk generate heat during HPT, but existing models for bulk samples underestimated the powder route’s thermal behavior. The experiments showed a rapid temperature increase during the first roughly 100 to 200 seconds, followed by a steady, essentially linear rise through 900 seconds of processing, reaching more than 25 kelvin. The team therefore proposed a new empirical model, adding a linear-in-time term to the established exponential saturation equations, capturing both the swift early heating of the powder compact and the sustained rise thereafter. This thermal evolution matters because even modest heating can activate diffusion processes that shape the final nanostructure.

X-ray diffraction analysis using classical and modified Williamson-Hall methods quantified the lattice defects driving the strengthening. Crystallite size dropped from about 843 nanometers in the initial powder to roughly 20 nanometers after a single HPT turn, with dislocation densities exceeding ten to the fifteenth per square meter and microstrain roughly doubling; these parameters then stayed nearly constant through 15 turns. The refined dislocation analysis accounted for strain anisotropy around dislocations, a hallmark of severely deformed face-centered cubic metals, and yielded lattice parameters consistent with microscopy observations.

The nanoindentation data also revealed what actually controls plastic flow in the nanostructured alloy. Strain-rate sensitivity remained in the range of about 0.03 to 0.04, while activation volumes of roughly 5 to 6.5 cubic Burgers vectors indicated that deformation is governed by diffusion-mediated dislocation activity along grain boundaries — essentially grain boundary sliding accommodated by boundary diffusion. From these measurements, the researchers estimated grain boundary diffusivities during indentation-induced plastic flow at room temperature that are far higher than thermal values measured by tracer techniques in coarse-grained material, corresponding to apparent activation energies of 85 to 93 kilojoules per mole. This apparent acceleration reflects stress-assisted boundary diffusion and the high density of nonequilibrium grain boundaries created by severe deformation, running counter to the sluggish diffusion reputation of high-entropy alloys in their nanostructured state.

Together, the results establish high-pressure torsion powder metallurgy as a viable, single-step, room-temperature route to bulk nanostructured high-entropy alloys with densities near theoretical limits and hardness rivaling the best thermally processed material. By eliminating the high-temperature consolidation steps that plague conventional powder metallurgy and additive manufacturing, the approach sidesteps grain growth, oxidation, and segregation. As the team notes, further work is needed across wider ranges of turns, alloy compositions, and rotation speeds, but the demonstration that loose powder can become a dense, 30-nanometer-grained, exceptionally hard metal through pressure and shear alone opens a striking new chapter in metal processing.

Subject of Research: Room-temperature consolidation and nanostructuring of CrMnFeCoNi high-entropy alloy powder by high-pressure torsion, including microstructure evolution and deformation mechanisms

Article Title: Severe plastic deformation of powder-metallurgy CrMnFeCoNi alloy: Microstructure evolution and deformation mechanisms

Article References: Bhatta, L., Roush, B., Koledin, T. D., Norton, J. D., Lee, S.-Y., Jang, J.-I., Santala, M. K., Liss, K.-D., & Kawasaki, M. (2026). Severe plastic deformation of powder-metallurgy CrMnFeCoNi alloy: Microstructure evolution and deformation mechanisms. Journal of Materials Science: Metallurgy, 1(1), Article 13. https://doi.org/10.1007/s44492-026-00014-0

Image Credits: AI Generated

DOI: 10.1007/s44492-026-00014-0

Keywords: high-entropy alloy, CrMnFeCoNi, high-pressure torsion, severe plastic deformation, powder consolidation, nanostructure, grain refinement, nanoindentation, grain boundary diffusion, microhardness, X-ray diffraction, deformation mechanisms

The research team, led by Nafiz Ahmed Badhan and S M Yeasin Habib of Lamar University together with colleagues at Idaho National Laboratory and Clemson University, synthesized two alloys by vacuum arc melting: the four-element base alloy AlMoNbTi and its five-element counterpart AlCrMoNbTi, with chromium added in equimolar proportion. Both ingots were remelted at least five times to homogenize their chemistry and then subjected to hot isostatic pressing at 1200 degrees Celsius under 100 megapascals of pressure for four hours, a treatment designed to eliminate the casting porosity that plagues arc-melted refractory alloys. By removing such artifacts before testing, the authors ensured that the hardness values and corrosion currents they measured reflected the intrinsic character of each composition rather than flaws introduced during processing.

Microstructural analysis told the first part of the story. Backscattered electron imaging in the scanning electron microscope revealed that both alloys share a three-region architecture: a grey matrix, white island-like features, and black precipitates. Adding chromium enlarged the grey regions and increased the density of black, titanium-rich particles. Energy-dispersive X-ray spectroscopy mapping showed that aluminum dissolves relatively uniformly, while the white regions are enriched in aluminum, molybdenum, and niobium, the grey regions concentrate titanium and chromium, and the black particles are titanium-rich precipitates. Crucially, the alloy remains body-centered cubic with an ordered B2 superlattice, a structure long associated with the room-temperature brittleness of aluminum-containing refractory high-entropy alloys. The chromium addition did not dismantle this framework, but it did intensify elemental segregation within it, a change with profound consequences for how the material deforms and corrodes.

Nanoindentation, performed with a Hysitron TI 980 Triboindenter and a Berkovich tip at a maximum load of 20 millinewtons, captured the mechanical fingerprints of that segregation. The base AlMoNbTi alloy displayed hardness values ranging from 9.97 to 14.41 gigapascals, with a single, well-defined peak in the hardness distribution near 12.25 gigapascals. The chromium-containing alloy behaved very differently: its hardness distribution became bimodal, with one peak near 12.25 gigapascals and a second near 9.25 gigapascals, and its load-displacement curves scattered far more widely. Of 66 analyzed indents, roughly 42 percent landed on the softer phase. The overall average hardness of AlCrMoNbTi fell to 10.81 gigapascals, an 11.68 percent decrease relative to the base alloy, even as the reduced modulus rose modestly by about 3.1 percent to 200.57 gigapascals.

The authors trace this localized softening to a subtle disruption of crystallographic order. In the B2 structure of AlMoNbTi, aluminum and molybdenum preferentially occupy one sublattice while niobium and titanium occupy the other, and this long-range order strengthens the material by forcing dislocations to glide in paired super-dislocations across anti-phase boundaries. Drawing on prior work showing that chromium-enriched, titanium-depleted regions wet B2 domains with a more disordered A2-like phase, the team argues that chromium locally destabilizes the B2 superlattice and promotes a softer, chemically homogeneous A2 body-centered cubic phase. That loss of anti-phase-boundary strengthening, rather than the formation of hard Laves phases, which appear only in small volume fractions, best explains the bimodal hardness and the 11.68 percent softening. Notably, both alloys remain considerably harder than many other body-centered cubic high-entropy alloys reported in the literature.

The corrosion story is where chromium truly earns its reputation. Using electrochemical impedance spectroscopy in a 3.5 weight percent sodium chloride solution, the same brine concentration that approximates seawater, the researchers found that the chromium-containing alloy exhibited a 4.5 percent higher charge transfer resistance, meaning ion exchange at the metal-electrolyte interface slowed. More striking were the changes in the dielectric properties of the surface: effective double-layer capacitance dropped by 75.8 percent, and the phase-shift exponent moved 10.7 percent closer to the ideal capacitive value. Under the Helmholtz model, lower capacitance corresponds to a thicker protective layer, indicating that chromium promotes the growth of a denser, more ideal passive film on the alloy surface.

Potentiodynamic polarization tests reinforced the picture. The corrosion potential shifted positively from minus 403 to minus 356 millivolts versus the saturated silver-silver-chloride reference electrode, and the corrosion current plummeted by 44.2 percent, from 52 to 29 nanoamperes per square centimeter. Pitting potentials exceeded 1 volt versus the reference in both alloys, evidence of excellent resistance to passive film breakdown, though the chromium-bearing alloy showed a distinct secondary passivation region at potentials above 1.7 volts relative to its corrosion potential. This secondary passivation, the authors explain, is the signature of chromium’s celebrated repassivation ability: when the protective chromium oxide film breaks down at high anodic potentials, dissolved trivalent chromium ions hydrolyze inside incipient pits to form a chromium hydroxide barrier that stifles the pit and allows a new chromium-rich passive layer to reform.

Surface imaging after the polarization experiments made the improvement visible to the eye. The base AlMoNbTi alloy corroded in clustered, non-uniform patches, consistent with preferential attack along galvanically coupled, aluminum-rich pathways in the ordered sublattice network. The chromium-containing alloy, by contrast, showed a far more random and even distribution of pits, suggesting that chromium’s disruption of the ordered structure created a chemically more homogeneous surface with fewer weak points. Quantitative image analysis with ImageJ revealed that the average pitted area, as a percentage of the surface, fell from 20.02 percent to 12.28 percent, a reduction of approximately 38.66 percent attributable to chromium addition.

The authors ground these observations in thermodynamics and strengthening theory. Chromium raises the alloy’s valence electron concentration from 4.5 to 4.8, still comfortably within the body-centered cubic regime, and its smallest atomic radius in the five-element group increases lattice distortion and the atomic size mismatch parameter, which helps explain the heightened segregation. Calculations of solid-solution strengthening show that chromium itself contributes the largest single increment, roughly 1112 megapascals, more than aluminum at 705 megapascals, and that the total solid-solution strengthening of the disordered A2 phase reaches about 2060 megapascals. Combined with an estimated 68 megapascals from Orowan-type precipitation strengthening by the titanium-rich particles, the calculated hardness of the soft phase, about 7 gigapascals, lands reasonably close to the measured 9.15 gigapascals, with the residual gap attributed to grain and phase boundary strengthening and impurity effects.

The broader significance of the study lies in its demonstration that alloying additions in high-entropy systems cannot be judged by a single metric. Chromium simultaneously strengthens the passive film, enables self-healing repassivation, redistributes and suppresses pitting, and yet softens the load-bearing matrix by eroding B2 order. For engineers contemplating refractory high-entropy alloys for marine, chemical, or high-temperature service, the message is that composition must be tuned against the full property envelope. The research, funded by the U.S. National Science Foundation under award number 2138674, provides both a rigorous experimental baseline and a mechanistic framework for that tuning, showing that even within a family of famously complex metals, a single element can rewire the balance between durability and strength.

Subject of Research: Chromium alloying effects on the mechanical and corrosion properties of the AlMoNbTi high-entropy alloy

Article Title: Effects of Cr addition on the mechanical and corrosion properties of the AlMoNbTi high-entropy alloy

Article References: Badhan, N. A., Habib, S. M. Y., Fan, Z., Fan, X., Zhang, X., & Sun, C. (2026). Effects of Cr addition on the mechanical and corrosion properties of the AlMoNbTi high-entropy alloy. Journal of Materials Science: Metallurgy, 1(1), Article 18. https://doi.org/10.1007/s44492-026-00018-w

Image Credits: AI Generated

DOI: 10.1007/s44492-026-00018-w

Keywords: high-entropy alloy, AlMoNbTi, chromium addition, nanoindentation, corrosion resistance, electrochemical impedance spectroscopy, potentiodynamic polarization, pitting corrosion, B2 ordering, passive film, refractory alloy, segregation