This study investigates the effect of a chloride ion-rich environment on the global corrosion behaviour of IN718 alloy fabricated via Laser Beam Directed Energy Deposition (DED-LB). Electrochemical characterization was performed using open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) in 0.6 mol L- 1 NaCl solution, and directly compared with conventionally processed IN718. Microstructural analysis revealed pronounced differences between conventional and DED-LBfabricated IN718 in transverse, longitudinal, and top orientations, which clearly influence corrosion resistance. Despite the complex electrochemical response, the additively manufactured samples showed superior corrosion performance, highlighting the potential of the DED-LB technique. The transverse (icorr = 0.027 mA cm- 2; Epitting = 1.046 V/SCE), longitudinal (icorr = 0.030 mA cm- 2; Epitting = 1.076 V/SCE), and top (icorr = 0.057 mA cm- 2; Epitting = 1.067 V/SCE) orientations all outperformed conventional IN718 (icorr = 0.058 mA cm- 2; Epitting = 1.033 V/SCE). Finally, the manufactured samples exhibited higher impedance moduli values, irrespective of the immersion duration investigated (3 or 168 h), thereby evidencing the potential of the DED-LB technique.

Magnesium alloy WE43 has emerged as a promising candidate for biodegradable implant applications due to its elastic modulus, close to that of bone, and its well-established biocompatibility. However, its limited degradation resistance in aggressive environments restricts its clinical applicability. In this study, a nanostructured Nb2O5 thin film deposited by reactive sputtering was investigated with the aim of improving both the corrosion behaviour and biological performance of WE43 alloy. Morphological and compositional analyses of the WE43 alloy were conducted by using optical microscopy (OM), atomic force microscopy (AFM), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) and transmission electron microscopy (TEM), while structural analyses were conducted by Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Global corrosion behaviour was evaluated in 0.01 mol L-1 NaCl solution by using open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) over immersion periods of up to 912 h. In addition, in vitro biological assays were carried out to assess cytotoxicity and biocompatibility. The results demonstrate that the Nb2O5 coating acts as a protective barrier, delaying the initial corrosion process and modulating the inflammatory response. These findings highlight the potential of Nb2O5 thin films as an effective surface modification strategy to enhance the performance of magnesium-based biodegradable implants.

This work employed an integrated alloy-design strategy combining theoretical modeling, compositional optimization, and experimental validation, aiming to develop Cr- and Ni-rich multicomponent alloys with enhanced solid solution strengthening. Three quinary alloys (in at

This work aims to investigate the effects of chloride ion-rich environment on the global corrosion behaviour of the IN718 alloy fabricated using the Directed Energy Deposition (DED) by open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS) in 0.6 mol L-1 NaCl solution, comparing it to the conventional IN718 alloy. The results demonstrated that the DED method could produce corrosion resistance responses that are at least equivalent (top), and potentially superior (transversal and longitudinal), to those of the traditional IN718. Such findings underscore the effectiveness of the process in replicating, and possibly enhancing, the corrosion resistance properties of the IN718/DED alloy.

Chemical short-range order (CSRO), the non-random local arrangement of atoms in solid solutions, strongly affects the phase stability and performance of medium- and high-entropy alloys (M/HEAs). Despite its importance, the fundamental nature of CSRO formation remains contested: is it a formal thermodynamic transition? Here, investigating CoCrNi as a model system, we indicate that the main CSRO transformations observed in alloys might not be classical thermodynamic transitions, but instead a kinetic arrest phenomenon analogous to the glass transition. Combining atomistic simulations and in situ synchrotron dilatometry experiments enabled the study of CSRO evolution and its structural impact across multiple length scales. For example, CSRO-driven changes in bond lengths and bond distribution significantly impact the observed lattice parameter and volume, allowing Warren-Cowley parameter values to be determined over a full experimental temperature range. We demonstrate that the degree of CSRO and the apparent transition temperatures, defined here as the komplex reaction temperatures (Tkr), are not intrinsic material constants. Rather, they are path-dependent quantities governed by thermal history and diffusional constraints, directly reflecting the frozen CSRO state. Our findings clarify the thermodynamic and kinetic mechanisms underlying CSRO evolution and establish a framework to distinguish thermodynamic transitions under kinetic constraints from genuine kinetically arrested phenomena. Understanding this distinction is crucial for controlling CSRO during alloy design and processing and provides a foundation for future investigations exploring the implications of CSRO in advanced materials.

An Al-Cu-Fe alloy coating was deposited on the surface of diamond microcrystals via mechanical treatment of the powder mixtures in a planetary mill. The diamond crystals were 100 mu m in size and had shapes close to truncated octahedron and cuboctahedron. The Al62.5Cu25Fe12.5 alloy was chosen as a model material to demonstrate the possibility of the coating formation from a brittle alloy on a hard substrate. The treatment was performed in steel vials with no balls added. During the treatment, fine particles of the alloy deposited selectively on the {1 1 1} facets of the diamond crystals. The material transfer from the alloy particles to the diamond facets was explained by considering the interaction of the particles with the wall of the vial.

The present study investigates the effect of nanometric L12 precipitates on the microstructure, deformation microtexture, and recrystallization behavior of a low-stacking-fault-energy (SFE) FCC Cr29.7Co29.7Ni35.4Al4Ti1.2 (at. %) alloy. Two processing routes were employed: a solution-treated condition and an aged condition tailored to form L12 nanoprecipitates prior to cold rolling. Both conditions were cold rolled to 50% thickness reduction and subsequently annealed at 900 degrees C for different times to promote recrystallization. Microstructural characterization was performed using optical, scanning and transmission electron microscopy. Electron backscatter diffraction was used for microtexture evaluation. The aged condition exhibited a finer grain size during the early stages of recrystallization, indicating that the L12 precipitates retard recrystallization. TEM analyses revealed that recrystallized grains are free of the L12 phase, whereas unrecrystallized regions retain these precipitates, confirming their role in delaying recrystallization. Deformation microtextures in both conditions were weak and characteristic of low-SFE FCC alloys, dominated by Brass-, S-, and G/B-type components. The aged sample exhibited a higher fraction of the S component after cold rolling, suggesting that the presence of precipitates influences the evolution of deformation texture. After recrystallization, both conditions developed weak textures; however, the dominant recrystallization components differed, with Brass prevailing in the aged condition and S dominating in the solution-treated condition. These results demonstrate that nanometric L12 precipitates significantly influence recrystallization kinetics and texture evolution in medium-to-low SFE FCC alloys, promoting grain refinement and texture randomization without markedly affecting the final grain size or hardness after complete recrystallization.

This study develops a multifunctional porous quasicrystalline (QC) material from an Al-Cu-Fe-Cr alloy for efficient adsorption and catalytic degradation of Congo Red. By optimizing alkaline leaching conditions, the material's porosity, surface chemistry, and functional performance were tailored. An Al85Cu6Fe3Cr6 (at%) alloy produced by spray forming was leached in 10 M NaOH for 0.5-48 h to selectively dissolve aluminum and expose active sites. A systematic investigation of the structural evolution and surface properties was conducted, and the adsorption capacity and catalytic behavior of the prepared alloys were also evaluated. After 30 min of controlled leaching, an optimal macroporous structure was produced with 10.9% porosity and a positive surface charge of 7.2 mV. This enhances the electrostatic adsorption of CR, achieving 70% removal within 24 h while maintaining QC phases and accessible active sites. The material also demonstrated effective catalytic activity, achieving complete azo-bond cleavage in under 10 min, favored by oxidized Fe/Cr/Cu species.

The Ti-6Al-4V alloy is widely used in orthopedic and dental implants due to its excellent mechanical, corrosion, and biological properties. However, it exhibits several limitations that can compromise its performance in clinical applications. Notably, the alloy suffers from a high coefficient of friction, which can lead to increased wear and reduced longevity of implants under relative movement conditions. Additionally, Ti-6Al-4V shows susceptibility to localized corrosion in physiological environments, particularly in the presence of bodily fluids that may result in the formation of pitting. These challenges underscore the need for surface modifications that can enhance the alloy’s tribological performance, thereby improving its overall efficacy and durability as a biomaterial in medical settings. In this context, the manuscript presents applied and innovative research that assesses the impact of implementing nanostructured Nb2O5 coatings through the reactive sputtering technique on the wear performance of Ti-6Al-4V alloy under both air and artificial saliva (AS) solution conditions using a Pin-on-Disk apparatus. The nanostructured Nb2O5 coating demonstrated the ability to reduce the wear rate and volume by up to 88% without inducing any modifications to the Ra and Rt of Ti-6Al-4V, a feature that is desirable for applications in implantable devices. The reduction in wear can be attributed to the shift from adhesive wear mechanisms on uncoated surfaces to abrasive mechanisms on coated surfaces. This research highlights the strategic advantage of utilizing Brazil’s abundant niobium resources to advance biomaterial technology and facilitate applications that benefit public health.

Friction stir welding (FSW) has emerged as an alternative to conventional joining processes for high-strength metal alloys, offering advantages in material efficiency and cost-effectiveness. However, the microstructural changes induced by FSW influence the mechanical and corrosion properties of aluminium alloys. To address these issues, anticorrosive coatings based on niobium pentoxide (Nb2O5) deposited via the physical vapour deposition (PVD) technique appear as a promising strategy to mitigate corrosion in the FSW-affected regions. This study aims to understand the corrosion behaviour of the 2198-T8 alloy post-FSW (nugget zone - NZ) and evaluate the protective efficacy of Nb2O5 coatings. Global electrochemical analyses, including open circuit potential (OCP), potentiodynamic polarisation curves (PPc), and electrochemical impedance spectroscopy (EIS), were conducted in 0.6 mol L- 1 NaCl solution for the 2198-T8, 2198-T8/FSW, and 2198-T8/FSW/Nb2O5 specimens. A comparative analysis of the uncoated samples revealed that the NZ exhibited reduced corrosion resistance compared to the base material (BM). However, the Nb2O5 coating produced using the PVD technique was able to delay the appearance of pitting on the surface of the 2198-T8/FSW alloy in 0.6 mol L- 1 NaCl solution. The results demonstrate the efficacy of Nb2O5 coatings in safeguarding the 2198-T8/FSW aluminium alloy against aggressive chloride environments, thereby enabling a more effective application of innovative joining techniques such as the FSW process.

To enhance interaction with the host tissue and protect the metal surface, various surface treatments can be applied to dental implants. This study aimed to produce layer-by-layer (LbL) films by alternated immersion of the titanium sample into polyacrylic acid (PAA) and chitosan solutions, obtaining a PAA/chitosan bilayer architecture, seeking to improve the corrosion resistance. For this purpose, 03 experimental groups (n = 05) were performed: Ti-Cp (as control), Ti-Cp+8 bilayers PAA/chitosan, and Ti-Cp+12 bilayers PAA/chitosan. The corrosion behavior was assessed by using open-circuit potential (OCP), potentiodynamic polarization curves (PPcs) and electrochemical impedance spectroscopy (EIS) techniques, conducted in 0.9 wt% NaCl solution at a controlled temperature of 25 ± 1 °C. The samples were characterized morphologically and structurally by atomic force microscope (AFM), scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), and X-ray diffraction (XRD) techniques before and after the corrosion tests. The electrochemical results significantly highlight the beneficial influence of coatings based on PAA/chitosan in enhancing the corrosion resistance of titanium. These findings not only corroborate the feasibility of using alternative materials for the protection of titanium but also open new possibilities for the development of innovative coatings that can be applied within the biomedical sector, serving as mediators for medicinal purposes, particularly in osteoconductive interventions.

This investigation examined the efficacy of Nb₂O₅-based coatings, deposited by using the reactive sputtering technique, on the corrosion and corrosion-fatigue behaviour of 2198-T8 aluminium alloy used as aircraft material. Global corrosion behaviour was accessed by Open Circuit Potential (OCP), Potentiodynamic Polarization curves (PPc) and Electrochemical Impedance Spectroscopy (EIS) techniques in 0.6 mol L⁻1 NaCl solution. Fatigue crack growth (FCG) tests were conducted under controlled loading conditions in both air and saline environments. Comprehensive structural and morphological characterisations were performed using advanced microscopy and spectroscopy techniques, including Atomic Force Microscopy (AFM), Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDX), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Electron Backscatter Diffraction (EBSD). The results unequivocally demonstrated the protective nature of the coating, significantly enhancing the alloy's durability as evidenced by corrosion and fatigue-corrosion tests. These findings underscore the substantial potential of Nb₂O₅ coatings in extending the service life of 2198-T8 aluminium alloy when subjected to aggressive environments, thereby providing invaluable data for aerospace engineering applications.

This study investigates the impact of laser surface remelting (LSR) on enhancing the corrosion resistance of 316L stainless steel (SS), focusing on the mitigation of manganese sulfide (MnS) inclusions. Optimized LSR parameters, including an energy density of 2000 J/cm2 and power levels of 150 W and 300 W, effectively modify and solubilize coarse and acicular MnS inclusions, leading to a refined and homogeneous microstructure. The remelted samples exhibit a thicker, uniform chromium-oxygen-rich passive layer, particularly Cr2O3, significantly enhancing resistance to pitting corrosion. Electrochemical analyses, supported by the Power Law model and polarization curves, reveal that LSR improves passive film properties, with high resistivity values (rho delta) indicating superior electrochemical performance. The elemental redistribution of key alloying elements such as chromium and molybdenum further reduce micro-galvanic coupling effects. The results emphasize the synergistic effects of higher energy densities and power levels in restoring the corrosion resistance of the surface to be able forming protective passive films with increased uniformity and thickness. By demonstrating the ability to recover and optimize corrosion resistance, LSR emerges as a transformative surface engineering strategy for advancing material performance in environments prone to aggressive corrosion, providing valuable insights for demanding industrial applications.

The present work investigates the range of critical cooling rates required to form icosahedral quasicrystals during the solidification of an Al90Cu4Fe2Cr4 (

Besides solid solution strengthening, microstructural refinement is another approach that can enhance the mechanical strength of high entropy alloys. This can be achieved using the high cooling rates inherent to the laser surface remelting process. In this work, the surface of a novel arc-melted Cr35Mn5Fe5Co5Ni50 (

It is well known that microstructural refinement, a key strengthening mechanism in metallic alloys, can be enhanced by the high solidification rates inherent to laser surface treatment techniques. However, the influence of laser power on the microstructural evolution and hardness response of CoCrNi-based medium-entropy alloys remains insufficiently explored. In this study, the surface of arc-melted Cr45Co27.5Ni27.5 (at

5A06-O and 2219-T87 aluminum alloys are promising candidates for propellant tanks. In this study, refill friction stir spot welding (refill FSSW) with a 0.1 mm offset was applied to produce defect-free 5A06-O/2219-T87 welds. A Box-Behnken method and statistical analysis were used to optimize the processing parameters, by determining the influence of welding parameters on lap shear strength (LSS). Plunge depth was the most influential parameter on LSS. All joints failed through the weld seam, including those tested at -55 degrees C. Microhardness measurements showed a slight increase in the 5A06 sheet over time, while the 2219 sheet exhibited significant hardness reduction. Microstructural analysis revealed typical features of refill FSSW, including a heat-affected zone, thermo-mechanically affected zone, stir zone, hook, and joint-line remnants. Novel findings include the identification of an onion structure in the welds, characterized by fine equiaxed grains and nanoprecipitates that contribute to weld's hardness. This unique microstructure, formed under the thermal and mechanical conditions of the FSSW process, strengthens the material and enhances its mechanical performance. Stop-action tests provided insights into material flow and microstructural evolution during welding. While conventional refill FSSW could not produce defect-free welds, the findings highlight the potential of the 0.1 mm offset refill FSSW to enhance weld quality, supporting its application in aerospace components requiring high mechanical integrity across extreme temperature ranges.

Face-centered cubic (FCC) Cr-Co-Ni multi-principal element alloys are among the toughest materials ever designed. The optimal trade-off between strength and ductility shown by these materials is tied with their deformation evolution. Typically, their plastic deformation starts with dislocation slip, followed by mechanical twinning (i.e., twinning induced plasticity, TWIP) and, as strain levels further increase, phase transformation induced by plasticity (TRIP). This work evaluates the deformation substructure of a highly strained (achieved with high-pressure torsion) Cr40Co30Ni30 (at%) alloy with and without carbon alloying. After processing, the carbon-free alloy developed a typical substructure observed in FCC Medium/High-entropy alloys at later stages of straining, characterized by the presence of nanotwins and HCP lamellae, resulting in a 5.9 GPa hardness. In contrast, carbon addition induced grain refinement and suppression of the TWIP and TRIP effects. Notably, the Cr39.6Co30Ni30C0.4 alloy developed networks of stacking faults with partial dislocations and Lomer-Cottrell locks, which primarily contributed to a stronger hardening capability, resulting in an increased hardness of 7.3 +/- 0.8 GPa, 22 % (1.3 GPa) higher than the base alloy. These findings have important implications for better understanding the deformation substructure evolution of FCC multi-principal element alloys and can pave the way forward in regard to the design approaches for carbon-alloying in these materials.

In this work, the microstructure and sliding wear behavior of a spray-formed Al90Cu4Fe2Cr4 (at%) alloy was studied. Mechanical properties under compression and Vickers microhardness were also evaluated. The microstructure of the spray-formed material consisted of an alpha-Al matrix reinforced with two complex intermetallic phases, lambda-Al13Fe4 and Al13Cr2, which are binary based intermetallic structures, with significant amounts of the other elements of the alloy. The dry-sliding wear resistance of the composites was evaluated using a pin-on-disk test configuration, with normal loads ranging from 10 to 20 N and sliding velocities of 0.05-0.2 m.s-1. Alumina spheres were used as counter-bodies in these tests. The samples exhibited a high sliding wear resistance and showed almost no variation in the specific wear rates for all test parameters used, with values ranging from 7x10- 4 to 8x10- 4 mm3/N.m. The coefficient of friction also remained almost constant, around 0.4, and the main wear mechanism was the delamination of intermetallic particles. The results indicate an improved drysliding wear resistance at high normal loads compared to previously fabricated Al-matrix composites reinforced with quasicrystals and complex intermetallic phases. The mechanical properties of this alloy, fabricated in a single-step process, was in the same range as found for previous studies, of Al-matrix reinforced with micronsized quasicrystals and intermetallics, prepared by more complex processing techniques. The simplicity of the one-step preparation process used in this study contributes to the development of more efficient and costeffective tribological materials for various applications.

In this work an Al90Cu4Fe2Cr4 spray-formed alloy, originally consisting of an α-Al matrix with two crystalline intermetallic phases, Al13Cr2 and λ-Al13Fe4, was subjected to laser surface remelting. Different sets of parameters, including combinations of laser power, table displacement speed and laser beam diameter, were used. The laser track with the best combination of track geometry and microstructural refinement was selected for a detailed microstructural characterization, using transmission electron microscopy coupled with diffraction analysis. The mechanical properties were assessed by dynamic indentation tests. The surface remelted sample showed a microstructure consisting of refined icosahedral quasicrystals, with average dispersoid size below 1 μm, embedded in an Al-FCC matrix. This is the first time quasicrystal formation is reported for this composition. Additionally, the laser remelted material presented a substantial increase in the microhardness value compared to the substrate, from 167 to 205 kgf/mm2.