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Ni-free Ti-based Shape Memory Alloys composed of non-toxic elements have been studied as promising candidates for biomedical applications. However, high tool wear makes them complex to manufacture with conventional techniques. In this way, Additive Manufacturing technologies allow to fabricate complex three-dimensional structures overcoming their poor workability. Control of composition, porosity, microstructure, texture and processing are the key challenges for developing Ni-free Ti-based Shape Memory Alloys. This article reviews various studies conducted on the Additive Manufacturing of Ni-free Ti-based shape memory alloys, including their processing, microstructures and properties., Peer Reviewed, Objectius de Desenvolupament Sostenible::3 - Salut i Benestar, Postprint (published version)

The slow transition from an out-of-equilibrium glass towards a supercooled liquid is a complex relaxation phenomenon. In this Letter, we study the correlation between mechanical relaxation and equilibration kinetics in a Pd20Pt20Cu20Ni20P20 high-entropy metallic glass. The evolution of stress relaxation with aging time was obtained with an unprecedented detail, allowing us to pinpoint new interesting features. The long structural relaxation towards equilibrium contains a wide distribution of activation energies, instead of being just associated to the ß relaxation as commonly accepted. The stress relaxation time can be correlated with the equilibration rate and we observe a decrease of microstructural heterogeneity which contrasts with an increase of dynamic heterogeneity. These results significantly enhance our insight of the interplay between relaxation dynamics and thermodynamics in metallic glasses., Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant, Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.a - Per a 2030, augmentar la cooperació internacional per tal de facilitar l’accés a la investigació i a les tecnolo­gies energètiques no contaminants, incloses les fonts d’energia renovables, l’eficiència energètica i les tecnologies de combustibles fòssils avançades i menys contaminants, i promoure la inversió en infraestructures energètiques i tecnologies d’energia no contaminant, Postprint (author's final draft)

Objectives Laser surface micropatterning of dental-grade zirconia (3Y-TZP) was explored with the objective of providing defined linear patterns capable of guiding bone-cell response. Methods A nanosecond (ns-) laser was employed to fabricate microgrooves on the surface of 3Y-TZP discs, yielding three different groove periodicities (i.e., 30, 50 and 100 µm). The resulting topography and surface damage were characterized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). X-Ray diffraction (XRD) and Raman spectroscopy techniques were employed to assess the hydrothermal degradation resistance of the modified topographies. Preliminary biological studies were conducted to evaluate adhesion (6 h) of human mesenchymal stem cells (hMSC) to the patterns in terms of cell number and morphology. Finally, Staphylococcus aureus adhesion (4 h) to the microgrooves was investigated. Results The surface analysis showed grooves of approximately 1.8 µm height that exhibited surface damage in the form of pile-up at the edge of the microgrooves, microcracks and cavities. Accelerated aging tests revealed a slight decrease of the hydrothermal degradation resistance after laser patterning, and the Raman mapping showed the presence of monoclinic phase heterogeneously distributed along the patterned surfaces. An increase of the hMSC area was identified on all the microgrooved surfaces, although only the 50 µm periodicity, which is closer to the cell size, significantly favored cell elongation and alignment along the grooves. A decrease in Staphylococcus aureus adhesion was observed on the investigated micropatterns. Significance The study suggests that linear microgrooves of 50 µm periodicity may help in promoting hMSC adhesion and alignment, while reducing bacterial cell attachment., Peer Reviewed, Postprint (published version)

Alternative hard materials to traditional WC-Co are one of the main goals in the investigation efforts of both scientific and industrial communities. In this investigation, WC-based materials were designed and processed with different Fe alloys employing a powder metallurgy route. Two candidates were selected: FeCrAl and FeNiCr. The former showed the formation of aluminium oxides, which hindered a homogeneous metal-ceramic distribution. On the other hand, FeNiCr led to dense and optimised samples which were further characterised in terms of their mechanical properties and corrosion resistance. They revealed an excellent combination of hardness and toughness, comparable or even superior to industrial compositions containing Co. Selected Cr addition induced some segregation and formation of secondary carbides –in consonance with thermodynamic simulation results and as evidenced by optical microscopy, XRD and TEM analyses– with a decrease in the TRS value. However, massive nanoindentation tests revealed that it also led to improved intrinsic hardness of binder and composite (metal-ceramic) phases, as well as enhanced corrosion resistance in acidic media compared to Cr-free alternative and reference hardmetals., Peer Reviewed, Postprint (published version)

Precision edge preparation techniques for cemented carbides enable optimization of the geometry of tools’ cutting edges. These techniques are frequently used in high-stress environments, resulting in substantial improvements in tools’ cutting performance. This investigation examined the impact and evolution of cutting edge parameters and resulting surface finishes as a function of dry-electropolishing time on an end-mill. Findings demonstrate enlargement of the cutting edge radius, a decrease in surface roughness, and the mitigation of defects induced during previous manufacturing stages (i.e., smashed ceramic particles, burrs, chipping, etc.). Additionally, a direct correlation between dry-electropolishing time and primary cutting edges’ micro-geometry parameters has been established., Peer Reviewed, Postprint (published version)

The mechanical behavior of ceramic–metal (WC-Co) composites at small specimen level is subject to significant uncertainty due to the random assembly of (1) its constituent phases, (2) the crystal orientation of the WC grains, (3) the intrinsic residual stresses, and (4) the variable level of confinement of the metallic binder, within the contiguous network of much stiffer WC grains. In the existing literature, a Weibull distribution of strength is typically assumed at large specimen level. However, it is unknown whether this assumption can be carried over to small samples. Thus, the aim of this study is to shed light into the randomness in the mechanical strength of WC-Co composites, by using Monte Carlo simulations employing Latin Hypercube Sampling. The marginal distribution of the model parameters is assumed to be a grafted zero-threshold Weibull-Gaussian probability distribution, applied individually to the ceramic particles and the metallic binder using autocorrelation fields. The deterministic models are the recently calibrated microplane models M7WC and MPJ2 for the ceramic phase (WC) and the metallic matrix (Co) respectively. Test data in the form of strength histograms, gathered from literature on tensile tests conducted on nanowires of WC-Co composites, are used to calibrate the Weibull and Gaussian parameters, the grafting point locations and the autocorrelation lengths. The deterministic models M7WC and MPJ2 are assumed to be predictive in this study, as they were already calibrated in a previously published work by the authors. The finite element meshes used in the Monte Carlo simulations are generated using real tomography images, which easily captures the Gaussian part of the probability density function (pdf) without any random variables. This approach is shown to account successfully for the randomness observed in the strength of these ceramic–metal composites. Predictions are made for the strength distribution of differently sized nanowire specimen, Peer Reviewed, Postprint (author's final draft)

Tissue and organ phantoms with realistic anatomical features are becoming increasingly popular in the medical field due to their potential to revolutionize surgical planning and practice. Despite advancements in the production technology using 3D printing and development of materials, the availability of 3D printable materials that accurately replicate human organs’ mechanical properties is limited. Therefore, we developed a family of silicone gel-based inks that can be 3D printed using direct ink writing (DIW) with tuneable viscoelastic properties that mimic a wide range of soft tissues. The control over viscoelastic properties is achieved by fine tuning of silicone formulations with a rheology modifier to promote the encapsulating silicone oil. This strategy not only allows for the recreation of the viscoelastic behaviour profile of a wide range of soft tissues through amplitude and frequency sweeps but also is entirely compatible with DIW printing for medical model manufacturing. Thus, this study stands as one of the few in the literature presenting a DIW printing technology enabling the printing of silicone with such precise control over viscoelastic properties that it allows for different sensations to be experienced by the evaluating medical team., Peer Reviewed, Postprint (published version)

Laser surface texturing is a promising technique for improving the surface properties of metals. In this study, a nanosecond pulsed laser was used to perform surface texturing on a metastable austenitic stainless steel AISI 301LN. The effects of the number of laser passes (from 1 to 1000 passes) on the surface morphology, microstructure, and mechanical properties were investigated. The results show that the depth of laser tracks increases with the number of passes due to thermal accumulation. Increasing the number of laser passes produces a rougher surface, but beyond a certain value, a smoother texture is observed. The amount of a’-martensite phase induced by the laser increases with the number of passes, producing augments in hardness. However, again, this trend changes after a certain number of laser passes, and hardening saturates and even decreases. Therefore, selecting the appropriate laser processing parameters and number of passes is essential to control the dimensions of laser tracks and thus the desired surface texture and also to achieve the level of hardening., Peer Reviewed, Postprint (author's final draft)

5xxx series aluminum alloys are widely used due to their corrosion resistance and weldability. These alloys exhibit interesting behavior when subjected to severe plastic deformation (SPD). Different SPD techniques allow the processing of materials in sheet forms, such as Repetitive Corrugating and Straightening (RCS) and Cumulative Roll Bonding (ARB). In this work, sheets of the aluminum 5083 alloy were processed by RCS up to 2 passes. The objective was to study the microstructural evolution of the AA5083 under heat treatment and plastic deformation processes, with the aim of finding a good balance between the yield strength and ductility. The microstructure changes and the mechanical effects of the process were studied by X-ray diffraction, Inverse Pole Figures, EBSD, and tensile test. The results showed the obtention of characteristic recrystallization and deformation textures (cube and brass component); in particular, the brass component decreased to ~10 % due to the RCS process. The first RCS pass obtained the best balance between yield strength-ductility (sy = 170 MPa and maximum elongation ~ 8%). With the results obtained, it was concluded that the microstructure and the mechanical properties of the processes alloy were determined by the accumulative dislocations density, which stopped the cube texture progression, microstructure stabilizing the microstructure, regardless of the work hardening., Peer Reviewed, Objectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

The present work proposes to investigate the effect of an ultrahigh molecular weight silicone rubber (UHMW-SR) and two ethylene methyl acrylate copolymers (EMA) with different methyl acrylate (MA) content on the mechanical and fire performance of a fireproof acrylonitrile butadiene styrene copolymer (ABS) composite, with an optimum amount of ammonium polyphosphate (APP) and aluminum diethyl phosphinate (AlPi). ABS formulations with a global flame retardant weight content of 20 wt.% (ABS P) were melt-compounded, with and without EMA and UHMW-SR, in a Brabender mixer. During this batch process, ABS P formulations with UHMW-SR and/or EMA registered lower torque values than those of ABS P. By means of scanning electron microscopy (SEM), it was possible to observe that all ABS composites exhibited a homogenous structure without phase separation or particle agglomeration. Slightly improved interfacial interaction between the well-dispersed flame-retardant particles in the presence of EMA and/or UHMW-SR was also noticed. Furthermore, synergies in mechanical properties by adding both EMA and UHMW-SR into ABS P were ascertained. An enhancement of molecular mobility that contributed to the softening of ABS P was observed under dynamic mechanical thermal analysis (DMTA). An improvement of its flexibility, ductility and toughness were also registered under three-point-bending trials, and even more remarkable synergies were noticed in Charpy notched impact strength. Particularly, a 212% increase was achieved when 5 wt.% of EMA with 29 wt.% of MA and 2 wt.% of UHMW-SR in ABS P (ABS E29 S P) were added. Thermogravimetric analysis (TGA) showed that the presence of EMA copolymers in ABS P formulations did not interfere with its thermal decomposition, whereas UHMW-SR presence decreased its thermal stability at the beginning of the decomposition. Although the addition of EMA or UHMW-SR, as well as the combination of both in ABS P increased the pHRR in cone calorimetry, UL 94 V-0 class, Peer Reviewed, Postprint (published version)

Aiming to evaluate the influence of microstructure on residual strength of hardmetals, conical indentation is implemented and validated as a simple and practical methodology to introduce controlled damage. Work is carried out in three fine-grained WC-Co cemented carbides with different binder content. In doing so, a contact damage map is first constructed through combined use of a wide range of indentation loads, detailed inspection by means of optical/electron microscopy and sequential tomography. Threshold indentation load values, defining the transition from deformation into cracking phenomena, are then used as experimental variable for residual strength testing of indented specimens. Dummy indentations are included in single specimens for extracting additional post-mortem information. Microstructural effects on residual strength are determined by comparing the fracture resistance under four-point bending of indented specimens with respect to values determined for pristine samples. It is found that fracture toughness prevails over hardness as key parameter for inducing a gradual strength lessening, instead of abrupt resistance drops. Main reason behind it is the capability of tougher hardmetal grades to uniformly distribute and homogenize the damage introduced during conical indentation. This is supported by the differences observed in the interaction of imprint and cracking features along failure paths as well as in stable growth of fissures linked to dummy indentations under the application of an external load. This finally translates in enhanced resistance to crack extension and higher damage tolerance., Peer Reviewed, Postprint (published version)

The application of 3D printing to calcium phosphates has opened unprecedented possibilities for the fabrication of personalized bone grafts. However, their biocompatibility and bioactivity are counterbalanced by their high brittleness. In this work we aim at overcoming this problem by developing a self-hardening ink containing reactive ceramic particles in a polycaprolactone solution instead of the traditional approach that use hydrogels as binders. The presence of polycaprolactone preserved the printability of the ink and was compatible with the hydrolysis-based hardening process, despite the absence of water in the ink and its hydrophobicity. The microstructure evolved from a continuous polymeric phase with loose ceramic particles to a continuous network of hydroxyapatite nanocrystals intertwined with the polymer, in a configuration radically different from the polymer/ceramic composites obtained by fused deposition modelling. This resulted in the evolution from a ductile behavior, dominated by the polymer, to a stiffer behavior as the ceramic phase reacted. The polycaprolactone binder provides two highly relevant benefits compared to hydrogel-based inks. First, the handleability and elasticity of the as-printed scaffolds, together with the proven possibility of eliminating the solvent, opens the door to implanting the scaffolds freshly printed once lyophilized, while in a ductile state, and the hardening process to take place inside the body, as in the case of calcium phosphate cements. Second, even with a hydroxyapatite content of more than 92%, the flexural strength and toughness of the scaffolds after hardening are twice and five times those of the all-ceramic scaffolds obtained with the hydrogel-based inks, respectively., Peer Reviewed, Postprint (published version)

Aerogels are low density foam-like materials that are obtained from a sol-gel process in which the solvent used is replaced by air without collapsing the previously formed threedimensional structure. In this work, we have studied the properties of aerogels composites that have been generated only from natural substances, using gelatin as matrix, clay and tannic acid as modifiers and water as unique solvent. The aerogels were obtained through lyophilization. While pure gelatin aerogel behaves like an elastic and low-stiffness foam, the addition of tannic acid and clay allow obtaining high resistant foams, reaching of up to a 9- fold increase in the elastic modulus, maintaining very low densities ( 0.14 g/cm3). These increases were obtained, on the one hand, due to a change in the aerogel micro-structure that evolved from a layered towards a honeycomb one. On the other hand, the alkaline conditions employed lead to the oxidation of tannic acid that was then able to establish covalent bonding with the amino groups of gelatin. The presence of well-dispersed clay in the matrix significantly reduced the rate of thermal degradation of the compounds due to its rearrangement into a stable protective layer on the surface of the material. Under conditions similar to those developed in a fire, the compound exhibited low flammability and high resistance to the spread of fire thanks to the synergistic action between clay and tannic acid. The achievement of multifunctional properties in these natural aerogels, allows broadening its applications, making that eventually, can replace traditional petroleumderived foams, such as polyurethane, polystyrene or phenol-formaldehyde that have a notable environmental impact., Peer Reviewed, Postprint (published version)

The development of direct dimethyl ether (DME) solid oxide fuel cells (SOFCs) has several drawbacks, due to the low catalytic activity and carbon deposition of conventional Ni–zirconia-based anodes. In the present study, the insertion of 2.0 wt.% Ru-Ce0.7Zr0.3O2-d (ruthenium–zirconium-doped ceria, Ru-CZO) as an anode catalyst layer (ACL) is proposed to be a promising solution. For this purpose, the CZO powder was prepared by the sol–gel synthesis method, and subsequently, nanoparticles of Ru (1.0–2.0 wt.%) were synthesized by the impregnation method and calcination. The catalyst powder was characterized by BET-specific surface area, X-ray diffraction (XRD), field emission scanning electron microscopy with an energy-dispersive spectroscopy detector (FESEM-EDS), and transmission electron microscopy (TEM) techniques. Afterward, the catalytic activity of Ru-CZO catalyst was studied using DME partial oxidation. Finally, button anode-supported SOFCs with Ru-CZO ACL were prepared, depositing Ru-CZO onto the anode support and using an annealing process. The effect of ACL on the electrochemical performance of cells was investigated under a DME and air mixture at 750 °C. The results showed a high dispersion of Ru in the CZO solid solution, which provided a complete DME conversion and high yields of H2 and CO at 750 °C. As a result, 2.0 wt.% Ru-CZO ACL enhanced the cell performance by more than 20% at 750 °C. The post-test analysis of cells with ACL proved a remarkable resistance of Ru-CZO ACL to carbon deposition compared to the reference cell, evidencing the potential application of Ru-CZO as a catalyst as well as an ACL for direct DME SOFCs., This research has received funding from grant PID2021-126614OB-I00 funded by MCIN/AEI/10.13039/501100011033, Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación, and AGAUR, Agency for Administration of University and Research (Agència de Gestió d’Ajuts Universitaris i de Recerca) (2021 SGR 01053). Mohammad Rezayat also acknowledges the AGAUR Fellowship (FI-SDUR-2020) of the Generalitat de Catalunya for its financial support. Miguel Morales Comas is Serra Húnter Lecturer Professor, and he is grateful to the Serra Húnter program (Generalitat de Catalunya)., Peer Reviewed, Postprint (published version)

This article discusses recent advancements in the Laser Surface Transformation Hardening (LSTH) process applied to industrial metals. It focuses on examining the microstructure of the metal surface layer and explores different methods of performing LSTH to evaluate mechanical and surface properties. The study also investigates the utilization of various industrial lasers and simulation software for the LSTH process. The careful analysis of heat transfer and temperature control during LSTH aims to prevent the generation of surface defects like micro-cracks and surface melting. Finite element method (FEM) software effectively simulates the LSTH process. The research provides a comprehensive overview of recent developments in LSTH, categorized based on different metals and subsequent testing, highlighting its applications in the automotive industry. Electrochemical, wear, and microhardness tests are investigated to assess the potential applications of automotive metals., Peer Reviewed, Postprint (published version)

High Entropy Alloys (HEA) are materials consisting of a mixture of five or more elements in equal or relatively large proportions. They are a promising alternative material due to their desirable properties such as good wettability, high toughness, wear resistance, and temperature stability. Recently, the concept of HEAs has been extended to include high entropy carbides (HECs), which have garnered attention in the scientific community. In this study, the microstructure and micromechanical properties of two different binders, Ni and Co, were characterized for HECs composed of Ti, Ta, Nb, V, and W. A high-speed nanoindentation mapping technique was used to obtain hardness (H) and elastic modulus (E) cartography maps. It allowed for the assessment of the intrinsic mechanical properties of the HECs, binders, and interphases, as well as those of the global microstructural assemblage. A total of 40,000 imprints were performed in each grade, and the resulting data sets were statistically analysed using 1D and 2D Gaussian approaches. It is found that cartographical maps permit to satisfactorily relate microstructural features and mechanical properties of the constitutive phases through 1D deconvolution statistical analysis., Postprint (published version)

Ion implantation has been shown to improve adhesion strength of AlCrSiN coatings due to a synergic enhancement on fracture toughness and load bearing capability of the substrate that can potentially increase the in-service efficiency of coated cutting tools. In this work, AlCrSiN coatings deposited by PVD on WC-Co substrates implanted with Ti, Cr and N ion species have been processed. The mechanical properties and adhesion have been characterized by contact techniques and the residual stress of the coatings and substrates have been evaluated using FIB-DIC technique and Vickers indentation tests, respectively. An improvement of adhesion strength is obtained for treated substrates, especially for those implanted with titanium and chromium ions. This improvement is attributed to the introduction of residual stresses in the substrate, which increases its fracture toughness and enhances its load bearing capability., Work funded through The Spanish Ministry of Science, Innovation and Universities through grants PGC-2018-096855-B-C41, PGC-2018-096855-B-C42 and PGC-2018-096855-A-C44., Peer Reviewed, Postprint (published version)

Hot deformation of sintered cobalt during hot compression testing was investigated in the temperature range of 700–1000 °C and at strain rates ranging from 0.0005 to 0.1 s-1. Cobalt underwent considerable dynamic recrystallization (DRX) during hot deformation, with stress-strain flow curves exhibiting one or several peaks followed by significant flow softening and leading to a steady-state stress. Constitutive equations were used to derive the flow stress behaviour. A physically based model to describe the strain rate as a function of stress was suggested for temperatures ranging between 775 and 1000 °C. In this case, a creep exponent (n) of 5 indicated that the deformation mechanism was controlled by the glide and climb of dislocations. The activation energy coinciding with the one for self-diffusion of ferromagnetic cubic cobalt implied a diffusion-controlled mechanism and the presence of face-centered cubic (FCC) cobalt during deformation. Interestingly, the results at 700 °C could not be perfectly fitted to this model and exhibited a higher resistance to deformation. This revealed that the glide and climb deformation mode was close to the transition where glide mode was dominant, and thus mostly glide occurred at 700 °C, especially for the largest strain rates., Peer Reviewed, Postprint (published version)

Polymer-based aerogels are tough, low-density, and thermally insulating materials currently receiving increasing attention. In this work, robust all-natural aerogel composites have been obtained by incorporating nanoscale montmorillonite and tannic acid into a gelatin matrix via freeze-drying. The prepared aerogels exhibited low densities, good compressive properties, and low thermal conductivities. The significant improvement in the thermomechanical properties results from the strong bonding between gelatin and tannic acid. Under fire, the systems exhibited excellent flame retardancy with reduced thermal degradation rate and cone calorimeter burning parameters. A straightforward surface treatment with polydimethylsiloxane gave the aerogels exceptional and durable superhydrophobicity. These multifunctional composite aerogels are considered promising eco-friendly alternatives to synthetic polymer-based foams., Peer Reviewed, Postprint (published version)

Laser cutting is a widely used manufacturing process, and the quality of the resulting cuts plays a crucial role in its success. This research employed the Design of Experiments (DOE) to investigate the impact of input process parameters on kerf quality during the laser cutting of 5 mm polymethyl methacrylate (PMMA) sheets. Response surface methodology (RSM) was utilized to model the relationship between the input parameters and the kerf quality, with regression equations developed for each response using the Design Expert software. A statistical analysis revealed the significant effects of high laser power, cutting speed, and focal plane position on kerf quality. Optimization, guided by the desirability function, identified optimal parameter combinations that offered the most favorable tradeoff among various responses. Optimal conditions were found to involve a high laser power, a cutting speed ranging from 4 to 7 mm/s, and a focal plane position at the center. Experiments indicated the suitability of the models for practical applications. An overlay plot analysis revealed a weak negative correlation between the laser power and the cutting speed, while the focal plane’s position could be adjusted independently., M. Rezayat acknowledges the AGAUR Fellowship (FI-SDUR-2020) of the Generalitat de Catalunya for its financial support., Peer Reviewed, Postprint (published version)

This study investigates the use of Electron Beam Powder Bed Fusion (PBF-EB) spot melting on SDSS 2507, a material known for its high tensile strength, corrosion resistance, and welding properties. Spot melting, a localized melting technique, utilize a stationary beam to create melt pools before rapidly repositioning to form new ones, offering precise control over material properties in additive manufacturing. We conducted a design of experiments with 32 samples and analysed them using SEM, XRD, EBSD, optical microscopy, nanoindentation and statistical modelling. Elevated PBF-EB processing temperatures significantly influence microstructure and phase composition. XRD analysis identified the presence of the detrimental sigma phase. EBSD analysis revealed a composition primarily consisting of austenite (63 %) and sigma phase (33.5 %), with residual ferrite (3.5 %). Statistical modelling demonstrated that a combination of spot-time, spot distance, focus offset, and layer thickness was the most reliable predictor for density while area energy proved to be the most accurate predictor for hardness, with R2adj values of 0.766 and 0.802, respectively. Our study confirms that PBF-EB is capable of processing SDSS 2507 through spot melting, resulting in high-density samples at high productivity rates. The presence of sigma phase shows a need for post build heat treatment to achieve the desired phase distribution. This research enhances the understanding of the process and also holds promise for industrial applications., The research has been conducted with financial support from the Knowledge Foundation (Stockholm, Sweden). Work funded in part by the Spanish Ministry of Science and Innovation through grant PID2021-126614OB-I00., Peer Reviewed, Postprint (published version)

The development of zirconia dental implants has become increasingly popular over the last years due to the outstanding mechanical properties, superior aesthetic appearance and high biocompatibility of this material. However, premature implant failure as a result of an incomplete osseointegration still represents a major concern. In this sense, surface modifications have been applied to dental zirconia to improve the biological interactions of the implant with the surrounding tissue. Nevertheless, surface modification of zirconia is challenging due to the formation of a monoclinic phase associated with ageing and loss of mechanical integrity. This review focuses on the most common surface topographical modification strategies currently applied to zirconia, namely grinding, sandblasting, chemical etching and laser treatment. A comprehensive and comparative analysis has been performed to assess the effects of these techniques on the physicochemical properties, mechanical performance, hydrothermal degradation behavior and biological response of the modified surfaces., Peer Reviewed, Postprint (published version)

Today, welding methods for joining ferrous and non-ferrous materials have become increasingly popular. However, fusion welding processes face limitations such as the creation of unwanted compounds and thickness limitations, especially when working with special alloy elements, and for this reason, solid state welding methods such as butt resistance method have been considered. In the present study, butt-to-butt resistance welding of VCN steel has been investigated. In this research, in order to investigate the effect of electric current, the welding pressure was considered constant and equal to 20 MPa, and the current was adjusted from about 3000 to nearly 6000 amperes. The results showed that by increasing the current up to 3778 amps, the strength increases by 18%, and then with a further increase in the current up to 5280 amps, the strength decreases. Of course, it should be noted that the percentage of relative length increase does not change significantly in the samples. Also, the results of the microstructural investigation showed that the presence of martensite phase as well as carbides formed in the structure are among the reasons for the increase in hardness in the weld zone in the examined samples., Peer Reviewed, Postprint (author's final draft)

Laser surface texturing (LST) has emerged as a powerful technique for creating surface patterns on various materials, including metals, polymers, and ceramics. Among LST methods, laser wobbling surface texturing (LWST) offers distinct advantages over traditional surface modification techniques. It provides a precise and non-contact approach to customize surface properties without affecting the bulk material. This study investigates the effects of amplitude and frequency of LWST as a surface modification strategy to mitigate high-temperature corrosion in AISI 301LN stainless steel, representing the first investigation of its kind. The study extensively examines the impact of LWST on surface morphology, wettability, phase transformation, and microhardness of 301LN stainless steel. The results reveal that the wobbling frequency of LWST has a greater effect on the surface roughness than the wobbling amplitude. Higher surface roughness of LWST promotes the increase of the surface area and altered surface energy, resulting in an increased wetting behavior. X-ray diffraction analysis confirms a moderate phase transformation from austenite to martensite in the laser-treated samples, which increases the surface hardness compared to the non-treated material. Finally, the corrosion tests conducted in molten carbonate salt at 600 °C evidence a reduction of the corrosion rate around 20 %. LWST promotes the formation of denser oxide layer, improving its effectiveness as a protective barrier against further oxidation., This research was funded by Direcció General d'Indústria and ACCIÓ (Generalitat de Catalunya) to IMEM-CIEFMA in the INNOTEC project with grant number ACE034/21/000031, and Agency for Administration of University and Research (Agència de Gestió d’Ajuts Universitaris i de Recerca, AGAUR) (2021 SGR 01053). M. Rezayat also acknowledge the AGAUR Fellowship (FI-SDUR-2020) of the Generalitat de Catalunya for its financial support, Peer Reviewed, Postprint (author's final draft)

The generation of reliable data in the high cycle fatigue domain is crucial to support further metallurgic developments of fatigue optimized steel grades. Commonly employed for this aim, traditional standardized characterization methods are expensive and time-consuming. Thus, to circumvent these limitations, different accelerated fatigue testing methodologies have been proposed. In this work, the rapid fatigue test based on stiffness evolution is numerically reproduced using the finite element method for a specific grade of twinning-induced plasticity steel. A high cycle fatigue constitutive law grounded on the continuum damage mechanics framework is employed for this purpose. To adequately capture the material non-linear behavior observed in the experiments, a novel hardening–softening stress–strain curve for damage is proposed. The entire load history in the fatigue domain is modeled. A cycle-jump algorithm is used to improve the computational efficiency of the simulations. It is shown that a reduction of about 55% in the analysis elapsed time is reached by using this algorithm, while the result accuracy is maintained. Finally, the good agreement between numerical and experimental results, revealed by a maximum relative error smaller than 6.0%, evidences the potential of the present constitutive formulation to model the behavior of metals in the high cycle fatigue domain., This work has been done within the framework of the Fatigue4Light (H2020-LC-GV-06-2020) project: “Fatigue modeling and fast testing methodologies to optimize part design and to boost lightweight materials deployment in chassis parts”. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 101006844. The work has been also supported by the Spanish Government program, Spain FPU17/04196. The authors gratefully acknowledge all the received support. Finally, they acknowledge the support received by the Severo Ochoa Centre of Excellence (2019-2023, Spain under the grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033, Spain ., Peer Reviewed, Postprint (published version)

The extreme versatility of additive manufacturing (AM) as processing technology results in “AMed pieces” with intrinsic characteristics linked to the shaping route followed, which are also key for defining mechanical integrity. The latter requires validation by measuring the mechanical properties, at both macroscopic (global) and microscopic (local) levels; and thus, consideration of specific testing length-scale aspects. This work aims to study the correlation between microstructure and mechanical properties for a WC-12%wt.Co hardmetal grade produced via binder jetting 3D printing (BJT) and subsequent sintering. In doing so, macro- and micro- Vickers hardness as well as scratch tests, using different loads and indenter tips, are conducted. It is found that studied samples processed by means of BJT exhibit a microstructure consisting of a relatively wide carbide size distribution, including a significant volume fraction (higher than 15%) of carbides larger than 3 µm. This is a direct consequence of the relatively high sintering temperature needed for getting full dense specimens, when manufactured following this AM route. Meanwhile, mechanical properties are found to be isotropic, with hardness and scratch resistance values falling within ranges of those expected for hardmetals with similar binder content and mean carbide grain size. Very interesting, length-scale effects on testing are observed in terms of dispersion of measured hardness value as applied load decreases. These findings, together with similar ones linked to length-scale influence on scratch response, point out that effective selection of mechanical testing parameters become critical for studying and understanding phenomena such as elastic/plastic and deformation/fracture transitions in AMed hardmetals., Peer Reviewed, Postprint (published version)

Laser ablation has become an innovative treatment for cemented carbides, regarding edge rounding and surface modification, aiming to improve their tribomechanical performance. Meanwhile, the precision offered for this technique has also positioned it as an effective mean to generate micronotches used for evaluation of mechanical properties in structural materials. However, similar approach has not been attempted for hardmetals; thus, it becomes the main objective of this work. Dimple-like and elongated micronotches are introduced in one fine-grained WC-11%wtCo grade. In doing so, laser processing parameters are first optimized to attain micronotches with appropriated geometry and size, i.e. similar to critical flaws identified in broken pristine specimens. Success of the implemented approach is then validated through subsequent flexural testing, fractographic inspection and fracture mechanics analysis of the results attained on samples containing surface micronotches, as far as laser-induced residual stresses are taken into consideration. In this regard, elongated micronotches are found to exhibit lower residual stresses, and postulate themselves as the optimal option of the two micronotch types studied. The suitability of laser ablation for shaping artificial small-scale flaws opens a new route for introducing controlled defects, alike those intrinsic to processing or induced during service, key aspect for further understanding damage tolerance issues in cemented carbides., Peer Reviewed, Postprint (published version)

To control the semisolid processing of aluminum alloys produced by the additive manufacturing technique, an exhaustive knowledge of their rheological behavior is required. In the semisolid state, metallic materials can show rheological characteristics similar to those of polymers, so semisolid state shaping is one of the currently considered routes for additive manufacturing with metallic materials. In this work, an approximation of the rheological control of the A356 aluminum alloy for its subsequent 3D manufacturing was carried out at a very low shear rate. A continuous cooling rheometer was designed and used, evaluating the influence of different process parameters on the viscosity variation of the aluminum alloy in the semisolid state. The results show an anomalous flow variation, indicating dilatant, and not thixotropic behavior, for very low shear rates., Peer Reviewed, Postprint (published version)

Multilayered sheets of AA1050 and AA7050 Al alloys produced by hot accumulative roll bonding (ARB) are tested to estimate their forming limit diagrams (FLDs). Sheets processed with preheating at 450 and 500¿°C for up to six ARB cycles are submitted to Nakazima tests with an in situ digital image correlation system and tensile tests to analyze the mechanical behavior. X-ray measurements and electron backscatter diffraction are performed to obtain the crystallographic texture and the mesotexture, respectively, and thus characterize the heterogeneous microstructure. A bimodal grain size distribution is observed in these sheets since AA7050 layers present elongated and fine grain size with nanometric precipitates and AA1050 layers present coarser and equiaxed grains. In addition, texture analysis indicates both rolling and shear components in the sheets. The FLDs show that the forming properties did not follow the expected rule of mixtures when compared with monolithic alloy sheets. Overall, the multilayered AA1050/AA7050 processed by means of ARB at 500¿°C presents better formability than that at 450¿°C, due to the combination of lower anisotropy measured by the Lankford coefficients values close to 1 and low normal anisotropy ¿r values., Peer Reviewed, Postprint (author's final draft)

The extremely severe conditions at which cutting tools are exposed in hard machining operations require tool materials with outstanding mechanical properties. Excellent combinations of high hardness and fracture toughness are aimed to enhance wear and contact damage resistance; and thus, reliability of the tool. Here, spherical indentation is used to induce controlled damage, under monotonic loads, and to assess the resulting damage scenario of polycrystalline cubic boron nitride (PcBN). In doing so, two grades with different content of cBN particles as well as chemical nature of the binder are investigated. Systematic and detailed inspection of residual imprints, by means of optical and scanning electron microscopy, is conducted to document critical loads for damage emergence and evolution through different stages, as a function of increasing load and micro- structural assemblage. It is found that H-PcBN grade, with higher content of cBN particles and a metallic binder, exhibits higher resistance to crack nucleation as well as a more gradual transition between distinct damage scenarios. This enhanced response is linked to the concomitant increase of hardness and fracture toughness observed for that grade, as compared to the L-PcBN one, consisting of a significantly lower amount of superhard particles bound by a binder of ceramic nature. In-depth inspection of interaction between fissures and micro- structure indicates the existence of four different crack paths for both PcBN grades - transgranular through cBN particles, across the binder phase, and intergranular along either cBN/cBN or cBN/binder interfaces. Relative frequency of these crack paths as well as operative toughening mechanisms define the effective crack growth resistance of each PcBN grade. In this regard, a higher fracture toughness is assessed for H-PcBN, as a result of crack bridging by metallic ductile ligaments together with the effective barrier-like role played by substructural features within c, Peer Reviewed, Postprint (published version)

Samples of the metastable austenitic stainless steel AISI 301LN were subjected to laser treatment with a nanosecond pulsed laser. Scanning speed and laser power were considered as the main process input variables, while the geometrical dimensions of laser tracks (depth and width) and surface roughness were the process responses. The effects of the input parameters on the responses were statistically investigated using analysis of variance (ANOVA). Microstructural characterization of the laser-treated zone was carried out via optical and focus ion beam microscopy, X-ray diffraction, and electron backscattered diffraction, mainly to discern the induced martensitic transformation. Also, tensile tests were performed in specimens with and without laser modification, in order to assess a possible effect on the mechanical response of the steel. The results show that, by increasing the laser power and decreasing the scanning speed, the geometrical dimensions of the laser tracks augment, the surface becomes rougher, and the higher heat input induces more martensitic transformation, whereas tensile properties are not significantly affected., Peer Reviewed, Postprint (author's final draft)

Laser surface modification treatments have been applied to samples of a metastable austenitic stainless steel AISI 301LN. The amount of residual stresses and the presence of induced a´-martensite phase on the surface and subsurface of the samples, as a consequence of laser modification, have been investigated in this study. X-ray diffraction has been used to measure these values, which is a non-destructive method. Laser modification has been applied as parallel lines at a distance of 40 µm, using a laser intensity of 4 A and scanning speeds of 1, 3, and 5 bits/ms, frequency had a constant value of 1000 Hz. The results of the phase analysis show an increase in the a´-martensite present in the surface modified by the laser and that the sample corresponding to the lowest laser speed has the highest martensite fraction. Also, high tensile residual stresses were generated, more pronounced for the lowest laser scanning speed., Peer Reviewed, Postprint (published version)

The use of titanium and titanium-based alloys in the human body due to their resistance to corrosion, implant ology and dentistry has led to significant progress in promoting new technologies. Regarding their excellent mechanical, physical and biological performance, new titanium alloys with non-toxic elements and long-term performance in the human body are described today. The main compositions of Ti-based alloys and properties comparable to existing classical alloys (C.P. TI, Ti-6Al-4V, Co-Cr-Mo, etc.) are used for medical applications. The addition of non-toxic elements such as Mo, Cu, Si, Zr and Mn also provides benefits, such as reducing the modulus of elasticity, increasing corrosion resistance and improving biocompatibility. In the present study, when choosing Ti-9Mo alloy, aluminum and copper (Cu) elements were added to it. These two alloys were chosen because one element is considered a favorable element for the body (copper) and the other element is harmful to the body (aluminum). By adding the copper alloy element to the Ti-9Mo alloy, the elastic modulus decreases to a minimum value of 97 GPa, and the aluminum alloy element increases the elastic modulus up to 118 GPa. Due to their similar properties, Ti-Mo-Cu alloys are found to be a good optional alloy to use., Peer Reviewed, Postprint (published version)

n this study, the structural integrity of mullite (3Al2O3·2SiO2) films, deposited on silicon carbide (SiC) substrates using chemical vapor deposition (CVD), was investigated via increasing load nanoscratch tests. The films were configured by mullite columns of stoichiometric composition growing from a silica-rich layer in contact with the SiC substrate. Controlled damage was induced in the 3Al2O3·2SiO2 films at relatively low scratch loads. Radial and lateral cracking were applied until final delamination and repeated chipping were achieved as the load increased. The intrinsic integrity of the 3Al2O3·2SiO2 film and the performance of the coated 3Al2O3·2SiO2/SiC system, regarded as a structural unit, were analyzed. With the aid of advanced characterization techniques at the surface and subsurface levels, the configuration and morphology of the damage induced in the coated system by the nanoscratch tests were characterized, and the scratch damage micromechanisms were identified. Finally, the adhesion of the film, in terms of energy of adhesion and interfacial fracture toughness, was determined using different models proposed in the literature. The results from this investigation contribute to the understanding of the mechanical performance and structural integrity of EBC/SiC-based systems, which over the past few years have increasingly been implemented in novel applications for gas turbines and aircraft engines., Peer Reviewed, Postprint (published version)

High-strength steels are widely used in vehicle body-in-white, offering a good balance between crashworthiness and lightweight design. The increased requirements of heavier electric vehicles, in terms of fatigue resistance and crashworthiness, highlight that chassis parts have remarkable lightweighting potential. However, applying these grades in chassis parts is not straightforward, as the forming processes, like trimming, may introduce surface defects that compromise the fatigue resistance of the component. This work presents a material selection strategy for the applicability of high-strength steels in chassis parts of electric vehicles. The proposed approach allows the evaluation of the key parameters of the chassis parts in a simple way. The crash performance is evaluated through fracture toughness using the essential work of fracture (EWF) methodology. The method is applied to thin high-strength steel sheets employing double-edge notched tensile specimens (DENT). On the other hand, fatigue performance is investigated in terms of fatigue resistance for both notched and unnotched specimens. The results for different complex-phase and dual-phase steels show a good agreement between the EWF and the fatigue notch factor. The method could help apply high-strength steel to chassis parts, as designers will have a tool to focus the expensive fatigue tests on the best material candidates., Postprint (published version)

Determining the fatigue behaviour of metallic materials using standardised testing methods is costly and time-consuming. Therefore, several methods have been proposed to shorten the testing time and improve the fatigue optimisation of materials and components. This work presents a new fatigue testing method based on fatigue damage monitoring that allows determining the fatigue resistance in a short time and with few specimens. The presented method, named as the stiffness method, monitors the inelastic strains as an indicator of fatigue damage evolution. Strain measurements were carried out by digital image correlation techniques and showed to effectively follow damage evolution during fatigue tests. Results are convincing and more evident to obtain and discuss than other monitoring techniques, like temperature dissipation. In addition, the method overcomes the main limitations of the existing fast testing methods by avoiding the utilisation of complex apparatus, like infrared cameras or acoustic emission sensors. The approach has been validated in ten different metallic materials, as titanium and aluminium alloys, carbon steels, and stainless steels. The estimated fatigue limit was compared with values obtained following standardised tests, showing excellent agreement. Results allow pointing out the stiffness method as an efficient and effective tool for rapidly determining the fatigue behaviour of metallic materials, Peer Reviewed, Postprint (author's final draft)

Metastable austenitic stainless steels (MASS) are widely used in various industrial applications due to their exceptional compromise between mechanical properties and corrosion resistance. However, the mechanical properties of these materials can be further enhanced by surface treatments. This paper reviews various surface treatment methodologies used to improve the mechanical properties of MASS, with particular attention to laser treatments. The effects of these surface treatments on the microstructure and chemical composition in the thermal affected zone of the MASS are discussed, and their impact on the material’s mechanical properties, such as hardness, tensile strength, and fatigue life, are investigated in detail. Additionally, the paper highlights the limitations of these surface treatments and points out some areas where further research is needed. The findings presented can be used to guide the selection of appropriate surface treatment techniques for specific applications, ultimately improving the performance and lifespan of MASS in various industrial settings., Peer Reviewed, Postprint (published version)

An experimental austenitic twin-induced plasticity (TWIP) steel was deformed under hot torsion tests. Two different total equivalent strains (2.2 and 2.6) were employed in order to raise its yield strength while keeping reasonable toughness. The material was isothermally strained at 900 °C with a low strain rate of 0.05 s-1. The effects of torsional deformation on the microstructure, texture and mechanical properties of the TWIP steel were investigated and compared with the as-received samples. X-Ray Diffraction (XRD) measurements were performed to identify the phases present in the metal before and after the thermomechanical process. Scanning electron microscopy (SEM), Electron backscatter diffraction (EBSD), Orientation distribution function (ODF) analysis and tensile experiments complemented the investigation of this research. The main deformation mechanism changed from conventional sliding inside the grain to nucleated twinning from the grain boundaries, which led to the decrease of the grain size to less than 1 µm (UFG - Ultrafine Grains). The results indicate that the transition in the deformation mechanisms is dependent on grain size associated with the flow profile of the material. This was due to changes in the dislocation density within the grain and the movement of dislocations around the yield point. No martensitic transformation was detected during the strain and neither from the twinning mechanism in the microstructure after the torsion deformation. The best balance between high strength and good ductility (920 MPa and 52%) was obtained after the total equivalent strain of 2.6. It was verified that the employed thermomechanical schedule affects the displacement of the substructure with the formation of sub-grains influencing the hardening behavior, texture and yield strength of the metal., Peer Reviewed, Postprint (author's final draft)

This research explores the impact of Cu composition, heating temperature, and milling time on the production of copper-tin alloy nanoparticles. By employing design of experiments techniques, the study systematically evaluates these input variables and their effects on particle size, optical density, and number of colonies. The identification of new Cu3Sn phases in the nanoparticle structure contributes to the novelty of this research. The findings highlight the potential for optimizing copper-tin alloy nanoparticle synthesis and enhancing their antibacterial properties. Mechanical alloying is found to produce nanoparticles up to 15 nm in size. Increasing the percentage of copper leads to improved antibacterial properties. This work provides insights into the synthesis process of copper-tin mechanical alloying and their potential for antibacterial applications., Peer Reviewed, Postprint (published version)

In this comprehensive study, the multifaceted impact of laser surface texturing (LST) on AISI 301LN stainless steel is explored. Changes in the microstructure, mechanical properties, and grain characteristics are examined. The dynamic relationship between Schmid factor evolution and plastic deformation in this stainless steel alloy is unveiled through the analysis of grain statistics and individual grain scrutiny. It is revealed that LST initiates the formation of strain-induced a’-martensite, grain refinement, and substantial hardness enhancements. Notably, an a’-martensite crystalline size of 2.05 Å is induced by LST. Furthermore, a 12% increase in tensile strength is observed after LST along with an 11% boost in yield strength. However, reductions of 19% in elongation to fracture and 12% in the area reduction are experienced., This research was funded by AGAUR, Agency for Administration of University and Research (Agència de Gestió d’Ajuts Universitaris i de Recerca), grant number FI-SDUR 2020., Peer Reviewed, Postprint (published version)

Investigation of four different surface-shaping and finishing sequences is carried out on the surface integrity of a WC-10Co hardmetal grade. The surface conditions include grinding, electrical discharge machining and grinding, followed by mechanical and dry-electrochemical polishing using the DryLyte® technology. The evaluation includes the measurement of roughness, residual stresses, the Vickers hardness, indentation fracture toughness determination and the damage induced by conical contact response. By scanning electron microscopy, a systematic and detailed examination of the residual imprints is carried out to determine the critical loads for damage initiation and development across the different surface conditions. The results indicate that the use of dry-electrochemical polishing enables the attainment of polished surfaces without any corrosive damage to the metallic binder. Moreover, it retains the mechanical attributes reminiscent of the core material, comprising 85% that were initially induced via grinding., Peer Reviewed, Postprint (published version)

Ceramic membranes operating at high-temperatures are a key-technology for hydrogen separation processes. Cer-cer composites based on BaCe0.65Zr0.20Y0.15O3-d-Gd0.2Ce0.8O2-d have gained increasing attention as asymmetric membranes for H2 purification, for their high proton-electron conductivity, 100% selectivity, temperature and chemical stability, and intrinsic lower costs compared with the Pd–based technologies. Here, BCZY-GDC composite parts were successfully fabricated for the first time by microextrusion. Water-based pastes with different solid loadings and suitable rheological properties were formulated and printed in single or multilayer structures without nozzle clogging. After deposition, the samples were osmotically dried in concentrated PEG solutions in order to obtain cracks-free green bodies. The further process optimization allowed the production of planar BCZY-GDC ceramics to be potentially applied in asymmetric membrane structures. The mechanical properties of the as-obtained single and multilayer structures as well as of the interface between filaments were assessed through different nanoindentation techniques., Peer Reviewed, Postprint (published version)

The field of additive manufacturing (AM) has seen a transformation in the production of intricate and complex parts for various applications. Fused Deposition Modelling (FDM), among AM techniques, has garnered significant attention, particularly in fields like fibre-reinforced composites (FRC). In this study, the world of FDM-printed Polylactic Acid (PLA) components is explored, with a focus on how mechanical properties are influenced by infill percentages and layer widths. Through the utilisation of Response Surface Methodology (RSM), the optimisation of FDM-PLA 3D printing for a wide range of biomaterial applications is achieved, along with the unveiling of the potential for remarkable improvements in mechanical performance. Notably, a remarkable 91% reduction in surface roughness for PLA composites was achieved, accompanied by an impressive 25.6% and 34.1% enhancement in the tensile strength and Young’s modulus of fibre-reinforced PLA composites, respectively. This work, positioned at the crossroads of FDM, lays the groundwork for substantial advancements in the realm of additive manufacturing., Peer Reviewed, Postprint (published version)

Laser machining of the nickel oxide–yttria-stabilized zirconia (NiO–YSZ) composite in Solid Oxide Fuel Cells (SOFCs) may be an effective approach to enlarge the electrode–electrolyte interface and improve the cell performance. However, laser energy can cause thermal damage to the composite surface during the machined operation. In this work, the microstructure changes and the collateral damage caused by pulsed laser machining on the sintered NiO–YSZ of the state-of-the-art SOFCs were evaluated using complementary analysis techniques. Laser patterns consisting of parallel tracks on sintered NiO–YSZ were processed, varying the laser parameters such as frequency and laser beam energy density. The analyses evidenced a heat-affected zone (HAZ) limited to around 2 µm with microcracking, porosity reduction, and recrystallization. The changes in chemical composition, phase transformation of YSZ and mechanical properties at the machined surface were quite limited., Peer Reviewed, Postprint (published version)

This study explores pulsed Nd:YLF laser surface modification (LSM) effects on AISI 301LN stainless steel. Laser-treated surfaces underwent SEM characterization, revealing patterns and irregularities. Higher heat input surfaces showed significant microstructural changes, while lower heat input surfaces experienced less alteration. Increased laser spot overlap led to larger exposed areas and higher heat input, influencing groove width, depth, and surface roughness. Three-dimensional reconstructions illustrated the correlation between laser parameters and surface characteristics. XRD (X-ray diffraction analysis) and EBSD (Electron backscatter diffraction) analyses revealed a transformation from austenite to martensite, with an increase in the a’-martensite phase, particularly in patterns with high laser power, attributed to rapid cooling during laser modification. Grain size analysis indicated a 42% reduction post-treatment, enhancing the surface fraction of fine grains. Hardness measurements demonstrated an overall increase in laser-treated samples, linked to fine-grained microstructure formation, induced residual stresses, and the a’-martensitic phase., The authors would like to express their special gratitude to the Outokumpu for supplying the stainless steel and the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR) del Departament de Recerca i Universitats de la Generalitat de Catalunya for recognizing the Microstructural Design and Advanced Manufacturing of Materials Group as a consolidated research group (number 2021SGR01053). M. Rezayat acknowledges the AGAUR (FI-SDUR-2020) of the Generalitat de Catalunya for its financial support. H. Besharatloo acknowledges Ministerio de Universidades for the Margarita Salas grant., Peer Reviewed, Postprint (published version)

This article investigates the surface hardening capability of a metastable austenitic TRansformation Induced Plasticity (TRIP) stainless steel, particularly on AISI 301LN, by laser texturing. This technology produces microstructural surface changes in terms of both phase transformation and grain size modification and, as a direct consequence, the laser influences the surface characteristics, mainly hardness and roughness. In this sense, the key parameters (laser power, scanning speed and position of the focal length) were investigated by using a Design of Experiments (DoE) in detail to better understand the correlation between texturing parameters, microstructural and mechanical changes, always at the superficial level. From all the aforementioned information, the results show that the maximum surface hardening is obtained by increasing the laser power and decreasing the scanning speed. Furthermore, by reducing the focal distance, the depth of the microstructural evolution layer is more significant, while the width is less affected. Finally, a suitable model was developed to correlate the processing parameters here investigated with the resulting surface integrity, in terms of mechanical properties, by means of a regression equation., This research was funded by AGAUR, Agency for Administration of University and Research (Agència de Gestió d’Ajuts Universitaris i de Recerca), grant number FI-SDUR 2020., Peer Reviewed, Postprint (published version)

This paper presents a validated finite element modeling approach for simulating shear cutting, needing a minimal amount of experimental characterization. Only one uniaxial tensile test and one force–displacement relationship from a punching experiment are needed for calibration, with maintained prediction accuracy compared to more experimentally demanding approaches. A key ingredient is the observation that the Lode angle parameter is close to zero in the fracture region, postulating that the fracture strain only depends on stress triaxiality, with one free calibration parameter. The true stress–strain behavior is provided from inverse modeling of the tensile test, whereas the fracture model is calibrated using the punching test. The model is verified for different materials by comparing force–displacement curves for punching experiments not used in the calibration. The prediction error for the intrusion is below 4%. A validation is made for two setups. The local residual stresses are measured using Focused Ion-Beam Digital Image Correlation (FIB-DIC). The simulated values are within the experimental bounds. Cut edge morphology and plastic strains obtained by nano-indentation mappings are compared to simulation results, showing a decent agreement. For trimming, the cut edge morphology prediction performance decreases at 17% cutting clearance while it is maintained over the whole range for punching. The predicted hardness values have a mean absolute percentage error below 7.5%. Finally, the effect of element size and remeshing is discussed and quantified. The minimal experimental characterization and simulation effort needed, enables an efficient optimization of the cutting process in the industry., Peer Reviewed, Postprint (published version)

he unique combination of hardness, toughness, and wear resistance exhibited by heterogeneous hard materials, particularly cemented carbides (WC-Co), has made them preeminent material choices for extremely demanding applications, such as metal cutting/forming tools. The grinding post-processing of WC-Co induces changes in their surface integrity by modifying both constitutive phases through cracking the WC ceramic phase, introducing compressive residual stresses and/or inducing phase transformations (from face-centered cubic to hexagonal compact phase) in the metallic Co binder. A systematic micro- and nanomechanical study of different ground WC-Co grades (with distinct metallic Co binder content and WC particle size) is presented. In general, three different aspects are investigated: (1) assessment of the intrinsic hardness of the deformed layer from room temperature up to 600 °C, (2) correlation of the compressive residual stresses with hardness and elastic modulus maps by using high-speed indentation tests, and (3) evaluation of the oxidation process as a function of the testing temperature for the different ground WC-Co grades. It was found that the mechanical properties of the deformed ground layer for the different WC-Co grades slightly decrease at temperatures ranging between 400 and 500 °C, being this temperature non depending on the amount of metallic binder or WC grain size. This is attributed to different effects which take place simultaneously when the testing temperature increases: dislocation motion, reduction of compressive residual stresses and particularly, the generation of a heterogeneous oxide layer formed of CoWO4, WO3 and Co3O4., Peer Reviewed, Postprint (author's final draft)

There is a growing interest in zirconia ceramics due to their high flexural strength, excellent corrosion resistance and good biocompatibility. The assembly of advanced zirconia material with functions of sensing, actuation and controlling to solve the problems that may arise during its use is critical to ensure long-term service and performance. Within this context, the objective of this work is to analyse the structural health of zirconia samples by screen-printing silver-based conductive ink on the surface subjected to maximum load under flexural testing. In doing so, silver conductive ink was formulated using silver nanoparticles where polyvinyl pyrrolidone acted as the capping agent. Silver ink was then screen-printed onto zirconia samples and sintered at 200 °C. The resistance of the sensors was measured and the sensing capabilities of printed conductive patterns were investigated using the four-point probe method. Experimental findings displayed a reproducible direct correlation between electrical resistance change and strain resulting from surface displacement under applied load in four-point bending., Postprint (published version)

The development of microstructure and texture of twinning-induced plasticity (TWIP) steel sheet during ECAP at two temperatures (250° and 350°) up to four passes were investigated. The high chromium content is the differential of this TWIP steel, a chemical element that reduces the stacking-fault energy and increases corrosion resistance. By imposing ECAP, the volume fraction of twins, dislocation density, and yield strength significantly increase while ductility decreases. This study compared the effect of temperature during applied severe plastic deformation (SPD). Thin parallel slip bands’ high density was observed, and in addition to an intense micro shear, banding took place when pressing was continued by increasing the number of passes. The martensitic transformation was not detected in the deformation-twinning microstructure after more passes. The relationship between the microstructure, strain-hardening behavior, and mechanical properties was investigated after two different deformation schedules of ECAP. The best balance between high strength and good ductility (1915 MPa and 7%) was obtained after four passes at 250 °C and 350 °C. It was found that the quantity of ECAP pass affects the displacement substructure with the formation of shear bands, subgrains, and various variants of twins. These also influenced strain-hardening behavior, microhardness, texture, and ultimate strength., Peer Reviewed, Postprint (published version)