In recent years, the rapid growth of the Internet of Things (IoT) has increased the demand for maintenance-free power sources for sensors. Magnetostrictive energy harvesting is a promising candidate due to its durability. However, its low power output remains a major challenge for practical use. Although architectural optimization has been shown to enhance performance, the physical mechanisms by which complex structures influence energy conversion efficiency are still not fully understood.In this study, we propose a one-way stress-driven mechanics–electromagnetics coupled approach for architected magnetostrictive materials. The approach captures architecture-dependent magnetic flux redistribution arising from stress-dependent magnetic property changes. Using this approach, three Fe–Co configurations, namely Bulk, Cubic lattice, and Cubic-auxetic lattice, were systematically investigated. The numerical results suggest that the Cubic-auxetic structure shows the largest quasi-static linked-flux-change response among the three configurations. By transferring stress distributions from structural analysis to electromagnetic simulations, the proposed approach quantified inverse-magnetostrictive, stress-driven flux redistribution and showed that, unlike the Bulk, the Cubic and Cubic-auxetic lattices produce local stress concentration and altered internal magnetic field distributions, leading to larger magnetic flux changes. Experiments were used only to confirm ranking-level and trend-level consistency with the numerical analysis. The present approach provides a practical basis for pre-fabrication design and architecture screening of magnetostrictive energy harvesters.

Flow-Through Electrodes (FTEs) are widely used to intensify electrochemical processes due to their high specific surface area. Conventional FTEs, such as carbon felts or metal foams, rely on disordered porous structures with limited control over topology. Additive Manufacturing (AM) enables the fabrication of ordered and customizable electrode architectures, opening new opportunities for performance optimization [1]. In this work, we investigate nickel FTEs with a periodic octet-truss lattice structure produced by Laser Powder Bed Fusion (LPBF) (Fig. 1) and demonstrate how controlled porosity distributions can be used to optimize mass transfer and current distribution. The porosity is controlled through the fiber diameter of the unit-cells (Fig. 1). Both numerical simulations and experiments were conducted to study the influence of porosity and electrolyte velocity on hydrodynamic and electrochemical performances, with particular emphasis on the volumetric mass-transfer coefficient (kA e ), and current distribution. A porous-media model was developed to describe fluid flow, species transport, and electrochemical reactions within the FTEs. The electrode is considered as a continuous domain characterized by effective parameters that depend on local porosity and fluid velocity. Fluid flow in free and porous regions was modeled using Brinkman’s equation. Mass transport and electrochemical kinetics were described using the Newman model, including diffusion, convection, Butler–Volmer kinetics, and charge conservation in both the solid and electrolyte phases [2]. Effective transport properties were estimated using the Bruggeman model, while permeability and kA e were obtained from direct numerical simulations on few unit-cells (Navier–Stokes equations and dilute species mass transport in solution considering mass-transfer limitation C electrode =0). For electrodes with uniform porosity, simulations predict that concentration and electric potential gradients develop mainly along the flow direction, with nearly uniform transverse distributions. Experimental validation was performed using LPBF-produced nickel FTEs with uniform porosities ranging from 17% to 70% (unit-cell size = 2 mm, fiber diameter: 348–700 µm) (Fig.1) implemented in a filter-press reactor (Fig.2). The counter electrode was a 3D titanium-alloy electrode, enabling proper membrane sealing and preventing bypass flow between the electrodes and the membrane; a standard calomel reference electrode mounted on a capillary is placed at the inlet of the nickel FTE compartment (Fig. 3). Special care was taken to ensure the flow passes through the porous electrodes studied by preventing the flow from preferentially passing around the porous block. The FTEs were initially cleaned to remove contaminants and homogenize the surface state: immersion in HCl, rinsing with water, immersion in NaOH and final rinsing [3]. Limiting-current measurements for ferricyanide reduction were carried out in a filter-press reactor (Fig. 3), similarly following the procedure described in a previous study [4]. For porosities between 35% and 70%, experimental kA e values follow the same power-law dependence on fluid velocity u and porosity ε as predicted numerically, kA e = A.u β /ε α [2]. At lower porosities (17–35%), kA e values are significantly lower than expected due to LPBF manufacturing limitations, including limited resolution and partial pore clogging by trapped powder particles. Based on the experimentally validated kA e –porosity–velocity relationship, a Python-based bounded optimization method was implemented to determine spatial porosity distributions that homogenize mass transfer and current density across the electrode (uniform average current distribution density). The results demonstrate that graded-porosity FTEs can significantly improve current distribution and are promising for enhancing selectivity in electrochemical reactors. [1] Davis, J. T., Jayathilake, B. S., Chandrasekaran, S., Wong, J. J., Deotte, J. R., Baker, S. E., Beck, V. A., Duoss, E. B., Worsley, M. A., Lin, T. Y. (2024). Scientific Reports, 14(1), 10.1038/s41598-024-71765-w [2] Alkire, R., Gracon, B. (1975). Journal of The Electrochemical Society, 122(12), 10.1149/1.2134076 [3] Arenas, L. F., Ponce de León, C., & Walsh, F. C. (2017). Electrochemistry Communications, 77, 10.1016/j.elecom.2017.03.009 [4] Chauvet, F., Lohmuller, P., Laheurte, P., Serrano, K. G., Tzedakis, T. (2024). Chemical Engineering Journal, 490, 10.1016/j.cej.2024.151641 Figure 1

Powering the rapidly increasing number of Internet of Things (IoT) devices has become a critical challenge in recent years. Magnetostrictive energy harvesting has attracted considerable attention as a potential solution; however, the output of existing technologies remains insufficient for practical applications. In this study, a performance enhancement strategy based on geometric structural design is proposed. Fe - Co magnetostrictive alloys with multiple cubic-based lattice architectures were fabricated using laser powder bed fusion, and their energy harvesting performances were systematically compared. Under both impact and repetitive compressive loading conditions, the power generation performance consistently followed the order: Cubic-auxetic > Cubic > Bulk. Notably, the cubic-auxetic lattice achieved an output energy approximately 116 times higher than that of the bulk structure under an impact load of 500 N, demonstrating a viable pathway toward self-powered IoT devices and wireless sensors. This enhanced performance is attributed to a strengthened inverse magnetostrictive effect arising from local stress concentration and increased strain energy density induced by the lattice geometry. Moreover, the auxetic lattice reflects a bioinspired design principle observed in natural hierarchical structures. These results highlight geometric structural design as an effective and universal strategy for advancing magnetostrictive energy harvesting technologies to support the expanding IoT ecosystem. [GRAPHICS]

The adoption of the Laser Powder Bed Fusion (LPBF) process faces challenges due to a low productivity and high powder costs. Improvements in productivity can be achieved by increasing the laser power and the layer thickness. The present work explores an alternative approach by investigating the use of coarser particle size distributions in conjunction with thick powder layers. This approach potentially allows the valorisation of currently unexploited powder fractions in the LPBF process. In this work, blends of AISI 420 stainless steel powders are characterised in terms of their compaction dynamics and flow properties. The results obtained show that different levels of cohesion and compaction rate are found depending on the size ratio, the absolute size of the fine powder and its fraction. This work provides guidance for the selection of powder blends and opens up the possibility of their use in the LPBF process.

This study deals with the electrochemical and hydraulic performances of additive manufactured metal periodic lattice structure electrodes. These electrodes are fabricated by Laser Powder Bed Fusion (LPBF) from the titanium alloy TA6V and two structures have been studied: diagonal and octet-truss. They are integrated, as flow-through electrodes, in an electrochemical filter-press reactor. Current-potential curves are experimentally obtained by linear sweep voltammetry when feeding the reactor with a ferricyanide solution. From the measurement of the limiting current of ferricyanide ions reduction, the volumetric mass transfer coefficient kAe e is determined for several flow rates. Numerical simulations of fluid flow and mass transfer in these structures are also performed. Results show high values of kAe e for these structures (competing with carbon felt electrodes) while maintaining a high permeability (low flow resistance). The surface roughness, inherent to the additive manufacturing process, is found to induce a low (<= 10%) <= 10%) enhancement of mass transfer despite the roughness size (Ra Ra in the range 10-20 20 mu m) ) is close to the average thickness of the diffusion layer (for the investigated fluid velocities). As a result, these electrode structures show promising potential to be used in intensified electrochemical reactors by being further optimized to find the optimal internal dimensions that maximize mass transfer while limiting flow resistance.

A new metastable beta Ti-22Zr-11 Nb-2Sn (at%) biomedical titanium alloy was elaborated from elemental powders by in situ laser powder bed fusion technique (L-PBF). Iterative design of experiments was used to identify optimized manufacturing parameters to obtain dense and homogeneous parts (>99.3%) with low unmolten niobium fraction (<0.05%). The microstructural and mechanical properties of this alloy were investigated in its as-fabricated state and after two heat-treatments at 400 C and 700 C, respectively. The alloy, showing a beta-type microstructure, possesses a very low Young's modulus (-50 GPa) combined with a high tensile strength reaching about 1100 MPa after heat-treatment. These properties are very suitable for medical devices in osseous site such as hip prostheses or dental implants and the results were compared to the Ti-6Al-4 V ELI (wt%) medical grade fabricated from pre-alloyed powders. Thus, the present work demonstrates the significant potential of the in situ L-PBF technique to elaborate highly biocompatible titanium alloys with tailored chemical compositions.

In this work, experimental and numerical investigations are conducted to investigate the precision cutting cutting of Ti42Nb titanium alloy produced by laser-based powder bed fusion. Experimental precision cutting tests are carried out using precision turning lathe. Trials are performed with two cutting velocities of 60 m/min and 90 m/min and different feed rates, varying from 5 to 40 μ m/rev. For the numerical study, a porous crystal plasticity-based model is proposed to address the impact of anisotropy and microstructure heterogeneities of the polycrystalline material. The crystal plasticity-based model is identified using strain–stress curves obtained from compression tests performed under two strain rates and a wide range of temperatures. Numerical precision cutting simulations are performed in order to gain insight into the impact of crystallographic orientation and grain size on the machinability of the alloy. According to the results, the effect of the strain rates and the temperature on the thermomechanical behavior of the Ti42Nb alloy produced by laser-based powder bed fusion is correctly depicted. The model captured the strain localization on adiabatic shear band. According to the precision cutting simulations, the local variables such as temperature, damage and plastic deformation are strongly impacted by the crystallographic orientation and the grain size. Depending on the crystallographic orientations, the chip morphology changes form continues, slightly segmented to largely segmented.

In this work, a new class of iron-based high entropy shape memory alloys (HE-SMAs) have been designed, characterized, and optimized. These FeCuNiMnV alloys (FeMn-like) with damping properties at low and high temperatures are developed; a methodology is proposed to demonstrate how to preserve this effect from the memory loss observed on conventional damping alloys. The developed alloys are analyzed using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Their damping capacity is investigated using a drop weight test device instrumented with a digital image correlation system for the displacement measurement. It is compared with one of FeMnV, NiTi, CuAlNi, and 1050A alloys at different temperatures. The results show that the damping capacity is interesting over a wide range of operating temperatures. It has been established that the cocktail effect obtained by mixing Cu, Fe, Ni, Mn, and V elements allows for optimizing the damping capacity of the HE-SMAs. In addition, the sluggish diffusion may allow these HE-SMAs to prevent the premature aging that leads to a degradation of the damping behavior notably at high temperature. The variation of the composition of the Cu x Fe y Ni z Mn 20 V 11 alloys enables the adjustment of the alloying element content by favoring the appearance of the non-thermally activated martensite keeping hence a stable damping behavior from − 40 to 200 °C.

High-N Ni-free stainless steels are used for their excellent mechanical properties combined with their high corrosion resistance, especially for biomedical applications. Even though it is well-known that secondary hardening during annealing after cold working has been observed in many materials, this phenomenon was not reported for these materials, one of the best known being Biodur108©, although numerous efforts have been made to increase its hardness. In this work, thermomechanical treatments at low temperature of cold-deformed Biodur108© were conducted to increase the hardness. Hardness as high as 830 Hv was obtained. For this material, the annealing of a deformed sample at intermediate temperature leads to a secondary hardening phenomenon. The mechanisms responsible for this secondary hardening were analyzed. It was found that for deformed samples, annealing at 575 °C leads to the formation of small Cr2N precipitates along grain boundaries and sub-grain boundaries, and simultaneously with a new body-centered cubic (BCC) phase that possesses a super structure. The newly formed phases have sub-micrometric grain sizes.

The present work deals with the study of the damping capacity of β-metastable Ti–(24–26) Nb alloys. In this work, several methods have been used to characterize this damping. The impact tests were carried out using two test benches: high-speed impacts were carried out using a vertical firing pressure gun and low-velocity impacts were studied with a bullet drop test. In addition, an original approach of a dynamic mechanical analysis (DMA) is proposed in order to obtain more in-depth understanding of the relationship between microstructure, deformation mechanisms, and damping capacity. The specimens are studied at different microstructure states: single β, dual-phase β + α″, and martensitic phase. A correlation is established between the evolution of the damping factor as function of the applied strain and the occurrence of the corresponding deformation mechanisms. The stress-induced martensite mechanism contributes to the improvement of the damping factor. The highest damping capacity is observed for the dual-phase specimen (β + α″). It is shown that the contribution of both the reorientation martensite variants and stress-induced martensitic transformation lead to a damping capacity higher than a single deformation mechanism one.

The success of biomedical implantation is linked to osseointegration, depending on the mechanical loading of the bone interface. The large difference in stiffness between the host bone (30 GPa) and the usual implant material (over 100 GPa), as well as the absence of mechanical stress at the surrounding bone, induce a stress shielding effect, which leads to bone atrophy and implant loss. A recent work has shown the possibility to produce so-called second-generation titanium alloys. (3-type Ti alloys have been studied for biomedical applications, due to the composition of non-cytotoxic elements. Some TiNb alloys can reach after heat treatment a Young's modulus close to 35 GPa, which is really close to bone's one. Unfortunately, titanium and its alloys are well known for their poor machinability due to the hardness and low thermal conductivity. Machined surfaces of titanium alloys are also easily damaged (micro cracks, build-up edge, plastic deformation, heat-affected zones, and tension residual stresses) during the process. Studying process parameters is important to avoid these phenomena. The machinability of TiNb (turning, milling) has not been studied to date. Therefore, in this study, we examined the behavior of the TiNb titanium alloy for applications as a biomaterial in micro-cutting. Orthogonal cutting tests were performed on austenite and martensite states TiNb alloys and compared with Ti40 pure titanium. The aim was to evaluate the influence of the alloys and the cutting parameters on the evolution of the cutting forces, specific cutting energy, friction coefficient which are good indicators of machinability (C) 2022 The Authors. Published by Elsevier B.V.

OBJECTIVES:To assess the super-elasticity of CuNiTi wires (Ormco, Glendora, Calif) according to their Austenite finish temperature (Af) and to the imposed displacement. The secondary objective was to compare the wire dimensions with the stated measurements and to study interbatch variability.MATERIALS AND METHODS:10 types of CuNiTi wires (Ormco, Glendora, Calif) (n = 350) were investigated at 36 ± 1°C, with conventional brackets (Victory Series, 3M Unitek, Monrovia, Calif). Tensile test with coronoapical displacement ranging from 1 to 5 mm of the canine bracket was imposed. The wire dimensions were initially measured from two batches (n = 10).RESULTS:Dimensional heterogeneity varied by ± 2.00% compared to the manufacturer's data, and even up to 5.54% for 0.014-inch CuNiTi (P = .00069). However, all unloading forces were reproducible. In decreasing order, the forces delivered by a CuNiTi 27 were greater than those with CuNiTi 35 and 40. The super-elasticity was expressed only for displacements of 1 to 2 mm, at best up to 3 mm for 0.014-inch CuNiTi 27.CONCLUSIONS:The value of Af as well as the amount of imposed displacement seem to influence the expression of the super-elasticity of CuNiTi wires and the amount of corrected malocclusion. Among the tested wires, under these experimental conditions, 0.014-inch wire could be suitable as a first archwire. CuNiTi 35, therefore, seems to offer the best compromise among the force level, the expression of super-elasticity and the amount of malocclusion correction.

In this work, an analytical oblique cutting model has been proposed. This model is building on a one-dimensional approach for which the chip is formed by shearing within the primary shear zone. The impact of the material anisotropy is considered through a crystal plasticity-based constitutive model. The cutting forces and the corresponding specific energies are estimated using the physical-based normal shear angles procedure and Merchant’s normal shear angle procedure. The model is validated using the experimental data obtained from the literature. According to the results, the numerical and experimental findings are in good agreement. The model is then used to evaluate the impact of the crystallographic orientations and the machining parameters during oblique turning. The results show that the impact of the machining parameters on the cutting forces is correctly depicted. It is also demonstrated that whatever the crystal orientations are, the signature of cutting forces during oblique turning shows a fourfold symmetry. In addition, the variation of the cutting forces according to the rotation angle follows the evolution of the associated cumulative shear strain required to accommodate the plastic deformation. Finally, the simulations demonstrate that the chip flow angle, which has a significant effect on chip control, is greatly affected by the orientation of the single crystal.

In order to simulate micromachining of Ti-Nb medical devices produced in situ by selective laser melting, it is necessary to use constitutive models that allow one to reproduce accurately the material behavior under extreme loading conditions. The identification of these models is often performed using experimental tension or compression data. In this work, compression tests are conducted to investigate the impact of the loading conditions and the laser-based powder bed fusion (LB-PBF) building directions on the mechanical behavior of β-Ti42Nb alloy. Compression tests are performed under two strain rates (1 s−1 and 10 s−1) and four temperatures (298 K, 673 K, 873 K and 1073 K). Two LB-PBF building directions are used for manufacturing the compression specimens. Therefore, different metallographic analyses (i.e., optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), electron backscatter diffraction (EBSD) and X-ray diffraction) have been carried out on the deformed specimens to gain insight into the impact of the loading conditions on microstucture alterations. According to the results, whatever the loading conditions are, specimens manufactured with a building direction of 45∘ exhibit higher flow stress than those produced with a building direction of 90∘, highlighting the anisotropy of the as-LB-PBFed alloy. Additionally, the deformed alloy exhibits at room temperature a yielding strength of 1180 ± 40 MPa and a micro-hardness of 310 ± 7 HV0.1. Experimental observations demonstrated two strain localization modes: a highly deformed region corresponding to the localization of the plastic deformation in the central region of specimens and perpendicular to the compression direction and an adiabatic shear band oriented with an angle of ±45 with respect to same direction.

Energy harvesting using magnetostrictive materials is currently attracting significant attention. The additive manufacturing process can produce such materials with excellent energy-harvesting performance and various required properties, including mechanical properties—by optimizing the lattice structure of the material. This study optimized the manufacturing parameters of a laser powder bed fusion process to produce a magnetostrictive Fe52–Co48 alloy. We evaluated the energy-harvesting performance of a Fe52–Co48 alloy plate with a honeycomb structure subjected to vibrations and impacts. We compared the results with a fully dense structure and found that the honeycomb structure resulted in a lower resonant frequency. In addition, the honeycomb structure exhibited a power density 4.7 times higher than that of the fully dense structure in a vibration test and 4.9 times higher than that in an impact test. The honeycomb structure is thus an attractive structure for obtaining power efficiently. Furthermore, honeycomb structures and other designs can reduce the weight of a Fe52–Co48 alloy plate and improve its sensitivity for use as a particulate-matter sensor.

To obtain a functional part from additive manufacturing (AM) technologies, some surfaces require post-processing by machining. An approach is developed using additive manufacturing supports as a clamping device for the milling operation. A model combining an analytical approach to determine the cutting forces with a finite element model (FEM) to predict the dynamical response of the workpiece-supports system is proposed. The complex structure of the supports is homogenized with a simplified geometry with equivalent stiffness and mechanical properties. A case study from the biomedical field is proposed: the finishing operation of a custom-made maxillary reconstruction plate is simulated. A parametric study is proposed with: (1) two different lattice geometries used as support structures; (2) up and down milling; (3) different depths of cut.

Damage initiation and propagation are widely impacted by pores distribution induced during additive manufacturing (AM) processes. More specifically, the porosity can strongly affect the thermomechanical behavior of titanium alloys in the case of Selective Laser Melting (SLM). The present work examined the impact of SLM process parameters on microstructure characteristics, mechanical properties, and surface integrity of the Ti6Al4V titanium alloy. Different metallographic analyses (i.e., Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD)), density measurement and surface characterizing were carried out to investigate the effect of various process parameters (laser power and scanning speed) on the damage behaviors in terms of fracture surface and cracks initiation sites of the alloy.