The low density of Mg alloys makes them advantageous in lightweight structures for transportation, reducing energy costs and CO2 emissions. However, the production of Mg alloys is energy intensive and produces large amounts of waste, weakening the advantage of Mg alloys as a green material. A solid-state recycling method incorporating spark plasma sintering (SPS) and friction stir processing (FSP) has been proposed to recycle Mg-Y-RE alloy scraps produced during the machining process. In the first step, SPS rapidly turned scraps into a consolidated disk, with coarse grains, second phases and large pores. In the following FSP step, dynamic recrystallisation refined grains to about 1.2-3.0 mu m. Large second phases were partly re-dissolved into the matrix and redistributed. Pore size and fraction were reduced and a more densified disk was then obtained. The FSPed disk exhibited a yield strength (YS) of 190.3 MPa and an elongation (El) of 3.8%. Further ageing increased the YS to 226.5 MPa, whilst decreasing the El to 2.2%. The mechanical properties of the recycled material are comparable to cast and additively manufactured counterparts. It offers a possibility of the combination use of powder metallurgy and plastic deformation to achieve solid-state recycling of Mg alloys.

Tungsten borides are a class of superhard materials known for their excellent mechanical properties. However, little information is available on their high-temperature friction and wear behavior. In this study, a dense WB coating was successfully fabricated on a tungsten substrate using powder-pack boronizing process. The tribological behavior of the coating was systematically investigated at temperature range from 400 degrees C to 800 degrees C in air, as well as at 800 degrees C in an argon atmosphere. The sliding tests revealed that, in air, the friction coefficient of WB coating increased considerably from 0.51 at 400 degrees C to 0.66 at 600 degrees C, and then decreased sharply to 0.16 at 800 degrees C. These changes were closely related to the nature of the oxidation products formed on the coating surface. At 400 degrees C, the ultrahard WB structure was preserved due to its excellent oxidation resistance, and wear primarily occurred on the counterbody. At 600 degrees C, severe oxidation led to the formation of abundant rod-shaped B2O3 and WO3 debris, which acted as abrasive particles and contributed to the increased COF. At 800 degrees C, substantial evaporation of B2O3 resulted in the formation of a WO3-rich tribolayer on the wear track and a mixed B2O3-WO3 transfer layer on the counterbody, leading to reduced friction coefficient. Meanwhile, the wear rate increased progressively from 3.7 x 10-5 mm3/N center dot m at 400 degrees C to 1.9 x 10-4 mm3/N center dot m at 800 degrees C, owing to the enlarged real contact area between the friction pairs. When friction test was conducted at 800 degrees C under flowing argon atmosphere, the oxidation of the WB coating was significantly suppressed. The formation of lubricating B2O3-WO3 layers on both the wear track-supported by the underlying hard WB coating, and the counterbody effectively prevented direct contact between the friction pairs. As a result, an ultra-low friction coefficient of 0.08 and a reduced wear rate of 7.9 x 10-5 mm3/N center dot m were achieved.

This study introduces a breakthrough in self-lubricating WS2u2013nitrogen (WSN) coatings engineered for demanding applications across industries requiring adaptive durability and high performance. Deposited via nonequilibrium reactive magnetron sputtering in N2-containing atmospheres, the WSN coatings demonstrate exceptional tribological behavior across a range of extreme conditions, including constantly discrete high temperatures, ramping temperatures either during heating or cooling and wide temperature cycling from room temperature to 400 u00B0C. The WSN coatings exhibit an extremely low coefficient of friction (CoF = 0.02) up to 400 u00B0C, with high thermal stability and superior triboperformance. Moreover, the coatings possess favorable tribo-reversibility under 400 u00B0C u2194 room temperature cycles. Transmission electron microscopy analysis verified the self-lubricating, tribologically reversible, and ultralow lubrication mechanisms of the WSN coatings. However, under high-temperature tribosliding, the WS2 layer still dynamically forms a self-organized, layered interface structure that continuously adapts to sliding conditions, ultimately enabling sustained superlubricity and tribological reversibility. Oxidation during high-temperature tribosliding actually has only a minor degrading effect on friction provided that the coatings retain sufficient sulfur to predominantly form WS2 lubricant agents. This study provides novel insights into the development of advanced tribocatings exhibiting adaptive ultralubrication under various temperature conditions.

Commonly used metallic biomaterials exhibit significant disadvantages, including releasing toxic metallic ions from CoCrMo alloy and the insufficient wear resistance of Ti-based alloys. This underscores the need for enhanced metallic materials for orthopedic applications. The optimal material must exhibit superior mechanical properties, high corrosion resistance, biocompatibility, and, crucially, exceptional tribocorrosion resistance. High Entropy Alloys (HEAs) are promising for fulfilling these requirements due to their remarkable combination of features that may be customised for individual purposes. The Ti27.78Zr27.78Hf27.78Nb8.33Ta8.33 at% HEA has garnered interest as a promising candidate for orthopedic applications. This alloy demonstrates outstanding electrochemical performance. However, a comprehensive investigation into its tribocorrosion behaviour has yet to be conducted. The current study employed the Electrochemical Noise (EN) technique to analyze the tribocorrosion behaviour of the alloy in simulated body fluid at 37 degrees C. The findings indicate that the alloy demonstrates similar tribocorrosion performance when compared to its competitors. Additionally, the examination of the surface status after performing the tribocorrosion tests revealed a marked decrease in corrosion resistance.

This study introduces a breakthrough in self-lubricating WS2-nitrogen (WSN) coatings engineered for demanding applications across industries requiring adaptive durability and high performance. Deposited via nonequilibrium reactive magnetron sputtering in N2-containing atmospheres, the WSN coatings demonstrate exceptional tribological behavior across a range of extreme conditions, including constantly discrete high temperatures, ramping temperatures either during heating or cooling and wide temperature cycling from room temperature to 400 degrees C. The WSN coatings exhibit an extremely low coefficient of friction (CoF = 0.02) up to 400 degrees C, with high thermal stability and superior triboperformance. Moreover, the coatings possess favorable tribo-reversibility under 400 degrees C <-> room temperature cycles. Transmission electron microscopy analysis verified the self-lubricating, tribologically reversible, and ultralow lubrication mechanisms of the WSN coatings. However, under high-temperature tribosliding, the WS2 layer still dynamically forms a self-organized, layered interface structure that continuously adapts to sliding conditions, ultimately enabling sustained superlubricity and tribological reversibility. Oxidation during high-temperature tribosliding actually has only a minor degrading effect on friction provided that the coatings retain sufficient sulfur to predominantly form WS2 lubricant agents. This study provides novel insights into the development of advanced tribocatings exhibiting adaptive ultralubrication under various temperature conditions.

304 stainless steel (304 SS) was coated with poly(aniline/vinylalcohol/aminophenol) as a bond coat, graphene nanoplates as a reinforcement agent, gabapentin as an inhibitor, and acrylic as a top layer to increase its anti-pitting durability in a chloride-contaminated medium. Long-term localized corrosion was evaluated using electrochemical noise measurement (ENM), shot noise theory, Hilbert, Weibull, and Gumbel functions. The polyaniline composite coating increased the noise resistance of 304 SS by more than 100 times after 1 month of exposure to the NaCl 3.5 wt% as a corrosive medium. Reinforcement of poly(aniline/vinylalcohol/aminophenol) coating with graphene and gabapentin has reduced the pit initiation rate and the maximum pit radius of 304 SS by more than 25 % and 43 %, respectively. The Hilbert spectra discovered the vital role of gabapentin on pitting suppression. In addition, the simultaneous presence of graphene and gabapentin shifted the transients to the higher frequencies at all times, indicating more tendency to uniform corrosion than localized. Finally, theoretical calculations revealed that graphene and gabapentin increased coating interaction/adsorption on 304 SS by ∼9 % (strong barrier). Consequently, excellent localized corrosion durability of 304 SS has been achieved thanks to the poly(aniline/vinylalcohol/aminophenol) reinforced with graphene and gabapentin.

A coating with excellent tribological behavior and corrosion durability was synthesized by chemical/electrochemical method from the composition of polyaniline (PANI), polyaminophenol (PAP), polyvinylalcohol (PVA), and reinforced with PANI/PAP/Gabapentin-functionalized Graphene nanoplates. Acrylic (AC) covered the composite coating as a top layer. According to the evaluations, G@PANI/PAP/GP-reinforced coating has 5 times more corrosion resistance than unreinforced one (on the 1st and 30th days). Not only has the corrosion resistance of PANI/PVA/PAP contained G@PANI/PAP/GP not decreased over time, but it has increased by similar to 20 %. The defect density of passive film under (PANI/PVA/PAP)/Acrylic coating containing G@PANI/PAP/GP is 10 times less than that of the (PANI/PVA/PAP)/Acrylic coating. G@PANI/PAP/GP decreased the friction coefficient and wear rate of PANI composite coating over time by similar to 47 % and 84 %. Furthermore, the simultaneous presence of graphene and gabapentin has increased the lubrication (R-sk = -0.24 mu m) and adhesion (13 %) of the coating. It is how a polyaniline-based composite coating with three mechanisms of passivation, corrosion barrier, and inhibition protects the 304 SS over time.

Fusion reactor materials for the first wall and blanket must have high strength, be radiation tolerant and be reduced activation (low post-use radioactivity), which has resulted in reduced activation ferritic/martensitic (RAFM) steels. The current steels suffer irradiation-induced hardening and embrittlement and are not adequate for planned commercial fusion reactors. Producing high strength, ductility and toughness is difficult, because inhibiting deformation to produce strength also reduces the amount of work hardening available, and thereby ductility. Here we solve this dichotomy to introduce a high strength and high ductility RAFM steel, produced by a modified thermomechanical process route. A unique multiscale microstructure is developed, comprising nanoscale and microscale ferrite, tempered martensite containing fine subgrains and a high density of nanoscale precipitates. High strength is attributed to the fine grain and subgrain and a higher proportion of metal carbides, while the high ductility results from a high mobile dislocation density in the ferrite, subgrain formation in the tempered martensite, and the bimodal microstructure, which improves ductility without impairing strength.

High-throughput methods can accelerate the development of metal alloys and (nano)composites, both empirically and as input to computational methods. This study introduces a new route to fabricating composite wires with longitudinally varying composition using the byproduct of stationary-shoulder friction stir channelling (SS-FSC); this sample format is attractive for a variety of rapid read-out options in the future. The concept is illustrated by preparing Mg composite wires with a longitudinally graded concentration of SiC-particles. Spark plasma sintering (SPS) was used to encode a step-change in SiC concentration within a feedstock billet. Subsequent SS-FSC transformed this discrete compositional step into a continuous, graded extruded wire. Micro-structural analysis revealed significant grain refinement from the SPS billet (44.3 f 2.3 mu m) to the SS-FSC wire (7.4 f 0.5 mu m), with even finer grains in SiC-loaded regions (5.1 f 0.5 mu m), attributed to particle-stimulated nucleation. Mechanical characterisation confirmed a hardness increase, from 65.8 f 1.2 HV3 to 68.9 f 2.7 HV3 (high SiC-content). This proof-of-concept study confirms the effectiveness of SS-FSC in producing high-quality wires with tailored microstructural and mechanical gradients. Additional compositions could be readily multiplexed in the original billet, providing a robust high-throughput technique for comprehensive structure-property investigations of advanced alloys and composites.

Recent studies show that precipitate-strengthened microalloyed steels offer strong resistance to hydrogen embrittlement due to hydrogen trapping by nanoscale precipitates. This study investigates how these precipitates interact with dislocations under strain, simulating service conditions. Two model steels were used: Ti-Mo steel with coherent (Ti,Mo)C precipitates and V-Mo steel with semi-coherent (V,Mo)C precipitates. Dislocation density was measured during in-situ neutron diffraction tensile tests, with and without hydrogen charging. Hydrogen increased dislocation density before straining but suppressed dislocation multiplication during loading, reducing overall dislocation strengthening, especially in Ti-Mo steel. The Ti-Mo steel showed greater sensitivity to hydrogen, attributed to reversible hydrogen trapping at coherent precipitate interfaces, and a greater increase in dislocation density. In contrast, V-Mo steel exhibited more irreversible trapping and a smaller increase in dislocation density. During tensile testing, with reversible hydrogen released to diffuse, subgrain formation in TiMo steel was restricted, as the higher concentration of diffusible hydrogen suppressed screw dislocation mobility. Consequently, fewer subgrain microstructures were generated, diminishing their effectiveness as barriers to crack propagation in Ti-Mo steel, compared to V-Mo steel. These results highlight the importance of selecting precipitate types that enhance irreversible hydrogen trapping, thereby improving the hydrogen resistance of steels.

Tribological contact often leads to surface deformation, resulting in a substantial increase in dislocation density and a considerable refinement in the microstructural scale. The extensive work hardening associated with this results in significant changes in the mechanical properties of the surface. It is not only the mechanical properties that change, but also the corrosion potential. In some cases, the surface changes enhance the wear resistance of the material. However, in other cases, higher wear rates are found with surface deformation that results in ultra-fine surface structures. Despite the importance of surface deformation, much is unknown about the mechanical properties of the wear induced surface layers. Nanoindentation provides useful information but does not give a good indicator of the ductility. The challenge is to test the mechanical properties of such a fine scale deformed structure. In this work, the micromechanical properties of Ti-6Al-4V worn surfaces after tribocorrosion testing were measured using an in-situ micropillar compression method in the chamber of a scanning electron microscope. Reciprocating tribocorrosion testing was undertaken in 25 vol. % Bovine Serum Albumin (BSA) in phosphate-buffered saline (PBS) solution against an alumina counterface, with a load of 0.5N and a speed of 20mm/s. Tests were conducted under Open Circuit Potential (OCP) conditions and at cathodic and anodic surface potentials, namely at +0.5V and -0.95V. The different test conditions resulted in different extents of surface deformation. This resulted in significant differences in the stress strain curves from the micropillar tests, both in terms of strength and ductility. The microstructure observed by subsequent TEM of the tested micropillars is correlated with the mechanical properties and the reasons for the different mechanical properties are discussed.

It is well known that the thermomechanical processing parameters affect the mechanical properties of dual-phase (DP) steels, but optimization still remains a key challenge. This work studied two interphase precipitation-strengthened DP steels based on V, Mo, and V, Mo, Cr microalloy additions. Hot-rolling was performed with a strain per pass of 0.2 and 0.4 before isothermal transformation at temperatures between 600 and 690 °C to determine the effect of these process parameters on microstructure, particularly interphase precipitation. The microstructure was carefully correlated with the mechanical properties. It was found that a higher strain during hot rolling increases the transformation kinetics of austenite to ferrite and also increases the volume fraction of the interphase precipitation within it, leading to higher strength values. The reaustenitization temperature before the isothermal transformation also plays an important role, with increased temperature reducing the segregation banding effect and increasing the amount of ferrite. The optimal reaustenitization temperature depends on the composition, being 1250 °C for the microalloyed steel with Cr additions and 1150 °C for the Cr-free microalloyed steel. A new method was used to calculate the yield strength of these DP microalloyed steels, including the strengthening contributors of each phase and the banding effect brought into one single expression that matches the experimental results.

There has been much research on steels strengthened by interphase precipitation, but the role of Cr remains unclear. Isothermal transformations have been performed at different temperatures to investigate the effect of Cr and Cr + Nb additions on the interphase precipitation resulting from the austenite-to-ferrite transformations in V-Mo based dual phase steels. Optical microscopy (OM) plus transmission electron microscopy (TEM) and tensile testing were used to characterize and correlate microstructural evolution to the tensile properties and the interphase precipitation formed during the austenite to ferrite (gamma ->alpha) transformation. It was found that an addition of 0.5 wt% Cr to V-Mo microalloyed steel accelerates the transformation rate of ferrite, producing a higher volume fraction of ferrite. Importantly, the addition of Cr reduces the diameter of the interphase precipitates giving an important contribution to the yield strength. A further addition of 0.03 wt% Nb to the Cr-V-Mo reduces the contribution made by the interphase precipitation and increased the grain refined contribution. A new method was used to calculate the volume fraction of interphase precipitation with TEM images from extraction replicas is presented and included in a root-mean-square model which includes the precipitation hardening made by IP on microalloyed DP steels to effectively predict their yield strength.

Ultrafine-grained (UFG) materials exhibit high strengths due to grain boundary strengthening, but grains can grow rapidly if post heat treatment is required, making it challenging to achieve grain boundary and precipitation strengthening simultaneously. Grain growth stagnation at 525 °C (0.87 Tm, melting point) was observed in a Mg-4Y-3RE alloy fabricated by additive friction stir deposition (AFSD), a novel solid-state additive manufacturing technology. The AFSD processing produced a UFG microstructure and two major second phases, Mg41RE5 and nanoparticles containing Y and O. After solid solution treatment (SST) at 525 °C for 72 h, no noticeable grain growth occurred. While Mg41RE5 particles dissolved into the matrix within 4 h of SST, the nanoparticles remained stable and unaltered. The observed grain growth stagnation is attributed to Zener pinning by these thermally stable nanoparticles. These new findings offer a novel approach to designing UFG materials with exceptional thermal stability for high-temperature applications.

Under nitrogen diffusion treatments, N -expanded austenite (gamma N) can form at the surface of self-passivating Fe-Cr, Ni-Cr, and Co-Cr alloys at low temperatures, which provides beneficial hardening and enhancements in wear resistance without reducing corrosion resistance. Given the wide research interests in multicomponent equimolar alloys, an equimolar quaternary FeCoNiCr high entropy alloy (HEA) was investigated after active -screen plasma nitriding at 430-480 degrees C in this study. Firstly, the formation of gamma N-FeCoNiCr case at 430 degrees C was demonstrated with the bright case appearance after metallographic etching, the lattice expansion under XRD, the FCC electron diffraction patterns and the shear bands under TEM. Secondly, the thick treatment cases at -9-16 mu m first indicated that N interstitial diffusion was not sluggish in the FeCoNiCr surface. Thirdly, analogous to stainless steels, the onset of dark regions in the etched gamma N-FeCoNiCr case was owing to the formation of a cellular mixture of CrN + gamma-(Fe, Co, Ni) nano -lamellae at elevated treatment temperatures. The residual bright regions in gamma N- FeCoNiCr at 480 degrees C showed -1-3 nm CrN nanoprecipitates with no substantial Cr segregation. Additionally, a significant nanocrystalline layer was seen at the topmost surface at 480 degrees C, which is most likely associated with the high substrate Cr content.

Polyaniline (PANI) coatings have the capability of in situ anodic protection of stainless steels (SSs). However, these coatings have a high degradation rate in sulfuric acid. Also, the protection of SSs in a medium contaminated with chloride ions is an unsolved challenge. Therefore, the present work aims to modify the electrodeposited PANI coating with different dopants to find the optimal coating for the anodic protection of 304 SS in chloride-contaminated sulfuric acid. Thus, CH3COO-, HSO4-, NO3-, H2PO4-, and NaSO4- were doped electrochemically in PANI to determine the most effective corrosion depressor. Density functional theory (DF)T calculations determined that the lowest Gibbs free energy (more spontaneous doping) is for HSO4- doping by 24 kcal/mol. The band gap energy is <0.5 eV for the PANI/H2SO4 coating, indicating the very high conductivity of this coating. Monte Carlo simulation revealed that the highest deformation energy is related to PANI/H2SO4 at 1877 kcal/mol (stronger adsorption). Mott-Schottky and energy-dispersive spectroscopy (EDS) results showed that PANI doped with sulfuric acid creates a p-type semiconductor (Ni-rich), while the rest of the dopants lead to the formation of an n-type semiconductor passive film (Fe/Cr-rich). Despite the relatively low corrosion resistance of PANI/H2SO4 in the early days, its resistance improved over time by more than 1 order of magnitude. Therefore, this seems to be a more favorable option for long-term anodic protection. Thus, in this work, the corrosion behavior of the passive film formed at the interface of PANI and SS was comprehensively evaluated.

CoCrMo has been used as an implant material for a long time due to its excellent combination of strength, corrosion resistance and biocompatibility. The formation of a thin passive oxide film on the surface of the material plays a crucial role in its performance. This passive film can be ruptured during contact between two surfaces, but usually reforms in short timescales. However, the reformation of the film depends on the availability of oxygen in the surrounding fluid. The oxygen level in human tissue, cartilage and synovial fluid, around which the implant is situated, is much lower than that in laboratory testing under open-air conditions. Moreover, the local oxygen concentration and pH values in the body vary from patient to patient, depending on the patient's health condition and other factors, which leads to variation in the corrosion resistance of metallic implants. Therefore, an implant that performs well at one time may still experience an undesirable level of corrosion at another. Thus, evaluation of the tribocorrosion of implant materials carried out in open-air conditions does not reflect the actual process the implants undergo once in the body, particularly if there is irritation due to injury or surgery. In this study, we investigate the tribocorrosion behaviour of CoCrMo in bioactive solutions under fully aerobic to anaerobic conditions with varying loads/contact pressures. The anaerobic condition leads to a reduction in wear rate and a reduction in the extent of tribofilm formation but does not have an appreciable effect on friction. The mechanisms are discussed in detail.

Recrystallization annealing is widely used to tailor the microstructure and enhance the performance of cold-deformed metallic materials. However, the underlying recrystallization mechanisms are debated, even with the use of cutting-edge characterization techniques. Here, we develop a Track-Rex toolbox to analyze quasi-in-situ electron backscatter diffraction (EBSD) datasets of two magnesium (Mg) alloys during static recrystallization via grain correlation. The results show that the recrystallized grains do not always grow; instead, they can shrink or even be consumed. This is attributed to the presence of newly formed recrystallized grains that possess a growth advantage over the old recrystallized grains. The rare earth containing Mg-2.4Zn-0.2Ce wt.% (ZE20) alloy exhibits a higher nucleation activity in the shear bands compared to the commercial Mg-3Al-1Zn (AZ31) alloy. Regardless of the nucleation timing and sites, recrystallized grains in the ZE20 alloy show consistent off-basal orientations, serving as the origin of the rare earth texture. Moreover, the off-basal texture of these recrystallized grains is further strengthened through preferential growth during subsequent annealing. On the contrary, the recrystallized grains in the AZ31 exhibit scattered basal orientations that grow uniformly, resulting in a weak basal texture.

An anti-corrosion and electroactive coating of PANI/PVA was electrodeposited on the 304 SS to improve the interface passive film. However, due to poor physical stability and tribological properties, PANI/PVA is copolymerized by various amounts (0.25-1 M) of 2-aminophenol (2-AP) and covered by a thin layer of acrylic (AC). According to the results, not only is the corrosion resistance of PANI/PVA/AP@AC about 100 times higher than PANI/PVA in 3.5 wt % NaCl (EIS), but its wear rate has also decreased by similar to 60% (pin-on-disk). Moreover, the friction coefficient of PANI/PVA/AP@AC has increased by 40% compared to PANI/PVA. The adhesion energy of PANI/PVA/AP@AC to the substrate is similar to 34% higher than that of PANI/PVA (pull-off). In addition, the nickel content of passive film under PANI/PVA/AP@AC reached 4.7% from similar to 0% for PANI/PVA (EDS). The defect density of the passive film decreased similar to 100 times by increasing the concentration of 2-AP to 1 M (Mott-Schottky). Moreover, uncoated 304 SS was protected galvanically with SS@PANI/PVA/AP@AC (with noise corrosion resistance of R-n similar to 10(6) Omega according to the galvanic corrosion evaluation). Finally, PANI/PVA/AP@AC remained intact after 160 h of immersion in the NaCl, and its potential reached +200 mV (electrochemical potentiometry). Therefore, PANI/PVA/AP@AC as a hybrid composite coating can sustain in situ anodic protection of 304 SS under harsh environmental conditions.

The drawbacks of commonly used metallic biomaterials like the release of toxic ions for the CoCrMo alloy and poor wear resistance for Ti-based alloys make it necessary to find a better metallic material as a new candidate for orthopaedic applications. In this work, different characterisation techniques were employed to investigate the relevance of a recently suggested TiNbTaZr HEA for orthopaedic applications. TiNbTaZr exhibited excellent mechanical properties and outstanding electrochemical behaviour. However, no significant enhancement in tribocorrosion wear behaviour is observed of TiZrNbTa over Ti6Al4V alloy, but the two materials exhibit different in-situ repassivation behaviour during tribocorrosion testing. A new approach of using the electrochemical noise EN technique in tribocorrosion investigation and data analysis is suggested.