Atomic-Scale Simulations Reveal How High-Entropy Alloy Coatings Shield Copper From Wear

At the scale of individual atoms, a scratch is not a scratch. It is a rolling storm of dislocations, stacking faults, and shattered crystal lattices, and how that storm unfolds determines whether a coated component survives years of service or fails within months. A team of researchers at Hung Yen University of Technology and Engineering in Vietnam has now mapped this atomic storm in unprecedented detail, using molecular dynamics simulations to trace exactly what happens when a sharp indenter drags across a polycrystalline CuCrCoFeNi high-entropy alloy coating deposited on a copper substrate. Their study, published in the Journal of Materials Science, offers some of the clearest evidence yet that these exotic five-element alloys act as remarkably effective sacrificial armor, absorbing the vast majority of deformation damage before it can reach the softer metal beneath.

High-entropy alloys have fascinated materials scientists since the early 2000s precisely because they break the rules that govern conventional metallurgy. Instead of building a metal around one dominant element with minor alloying additions, they mix four, five, or more principal elements in roughly equal proportions, producing a single disordered crystalline phase whose atoms jostle for position on a shared lattice. The resulting lattice distortion, chemical chaos, and sluggish atomic diffusion give these alloys extraordinary combinations of strength, ductility, wear resistance, and corrosion tolerance. When deposited as thin coatings on cheaper, softer substrates such as copper, they promise a way to upgrade the surface performance of everyday engineering components without the cost of building entire parts from expensive alloy systems.

The Vietnamese team, led by Thanh-Nga Trinh and corresponding author Anh-Son Tran, focused on the CuCrCoFeNi system, a canonical face-centered cubic high-entropy alloy that has become a workhorse for computational studies of deformation. Rather than simplifying their model to a single perfect crystal, the researchers constructed a genuinely polycrystalline coating, complete with grain boundaries and the complex internal architecture that real coatings possess. This choice matters enormously. Grain boundaries act as barriers that block, trap, and redirect dislocations, and a simulation that ignores them can dramatically misrepresent how a material responds to contact. The team used the LAMMPS simulation engine, the Atomsk toolkit for building the atomic model, Voronoi tessellation to generate realistic grain structures, and OVITO for visualizing and analyzing the resulting defect evolution.

The virtual experiment itself was elegantly simple in concept. A rigid spherical indenter was pressed into the coated copper and then dragged laterally across the surface, mimicking the nanoscratching tests that tribologists perform in the laboratory to measure friction and wear at ultrasmall scales. The researchers systematically varied two of the most important processing and service parameters: the scratching velocity and the depth to which the indenter penetrated the coating. By tracking the forces on the indenter, the friction coefficient, the pile-up of displaced material around the groove, and the evolving population of crystal defects, they could connect macroscopic tribological quantities directly to the atomic mechanisms that produce them.

The first headline finding concerns friction. The coefficient of friction, the dimensionless ratio that engineers use to characterize resistance to sliding, increased only slightly as the scratching velocity rose across the simulated range. This modest velocity sensitivity suggests that the alloy’s deformation response is dominated by rate-independent plasticity mechanisms rather than by thermally activated processes that would make friction strongly speed-dependent. In contrast, the coefficient of friction climbed sharply and significantly as the scratch depth increased. Deeper penetration forces the indenter into contact with a larger volume of material, engages more grain boundaries, and demands more extensive plastic flow to accommodate the moving tool, all of which translate into greater resistance to sliding and more severe near-surface damage.

Beneath the numbers, the simulations revealed a rich and evolving defect landscape. At shallow depths and moderate velocities, the primary response of the high-entropy alloy was the formation of an extensive network of stacking faults, the thin ribbons of misaligned atomic planes that characterize plastic deformation in face-centered cubic metals. These stacked fault structures wove through the grains of the coating, interconnecting and intersecting in ways that distributed the imposed strain across a broad volume rather than concentrating it along a single catastrophic shear band. This delocalization is a hallmark of why high-entropy alloys resist wear so effectively: the energy of the scratch is shared among countless small defect events instead of being funneled into a few large ones.

As the researchers pushed the simulation to higher velocities or greater depths, however, that elegant fault network began to break down. The stacked fault architecture gradually fragmented, giving way to a new population of defects that the team catalogued in detail: dislocation rings, ladder-like dislocation structures resembling the rungs of a nanoscale scaffold, and localized amorphous regions where the crystal lattice lost its ordered arrangement entirely and melted into a disordered glassy state. Far from being purely destructive, this fragmentation serves a protective purpose. Each of these defect structures dissipates a portion of the mechanical energy injected by the indenter, converting it into stored defect energy and localized atomic disorder rather than allowing it to propagate as a crack or as deep plastic flow toward the substrate.

Perhaps the most practically important result of the study is the fate of the copper substrate itself. Across the simulated conditions, the high-entropy coating withstood the overwhelming majority of the deformation, confining dislocations, faults, and amorphization to the coating layer and shielding the copper beneath from direct damage. Strikingly, this protective function persisted even when the scratch depth approached the full thickness of the coating, a regime in which one might expect the indenter to punch through and gouge the substrate. The coating’s ability to absorb and redistribute deformation right up to its own limits underscores why high-entropy alloy films are attracting attention as protective layers for copper components in electrical contacts, heat exchangers, and other applications where the underlying metal’s excellent conductivity must be paired with a far tougher surface.

The work also fits into a rapidly growing body of atomistic research on high-entropy alloy tribology. Recent simulations have explored how grain size and temperature govern the wear of CrCoNi medium-entropy alloy coatings, how crystallographic orientation shapes the scratching response of FeNiCrCoCu films, how L12 precipitates interact with dislocations during the nanoscratching of Al0.3CoCrFeNi, and how graphene reinforcement can further toughen these already remarkable materials. By extending this effort to a genuinely polycrystalline coating on a realistic substrate, and by isolating the specific roles of scratch velocity and depth, the Vietnamese team has filled in a piece of the puzzle that single-crystal and freestanding-film studies could not address. Their earlier work on the mechanical response and friction of CuCrCoFeNi coatings on copper provided the foundation; the new study adds the dynamic, depth-resolved picture of how damage evolves as the indenter moves.

For engineers, the practical message is clear and actionable. Because friction rises steeply with scratch depth while remaining comparatively insensitive to velocity, the priority in designing coated copper components should be ensuring that service loads never drive contact conditions deep enough to approach the coating thickness. Within that safe envelope, the coating’s internal defect machinery, stacking faults at low severity, fragmenting fault networks, dislocation rings, and amorphous pockets at higher severity, acts as a self-organizing energy-absorption system that no single-phase conventional coating can easily match. As molecular dynamics tools grow more powerful and interatomic potentials for multi-element alloys grow more accurate, studies of this kind are moving from academic curiosity toward genuine design guides, allowing researchers to screen coating compositions, thicknesses, and microstructures computationally before a single experimental sample is synthesized. The atomic storm inside a scratch, once invisible, is becoming a map that engineers can actually read.

Subject of Research: Molecular dynamics simulation of nanoscratching deformation mechanisms in polycrystalline CuCrCoFeNi high-entropy alloy coatings on copper substrates

Article Title: Nanoscratching behaviour and deformation mechanisms of polycrystalline CuCrCoFeNi high-entropy alloy coatings on Cu substrates: a molecular dynamics study

Article References: Trinh, T.-N., Tran, A.-S., Nguyen, A.-T., Chu, V.-T., & Vu, T.-Q. (2026). Nanoscratching behaviour and deformation mechanisms of polycrystalline CuCrCoFeNi high-entropy alloy coatings on Cu substrates: a molecular dynamics study. Journal of Materials Science, 61(43), 34198-34224. https://doi.org/10.1007/s10853-026-13785-7

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13785-7

Keywords: high-entropy alloy, CuCrCoFeNi, molecular dynamics, nanoscratching, coatings, tribology, friction coefficient, stacking faults, dislocations, copper substrate, wear resistance, deformation mechanisms