Femtosecond laser peening (fs-LP) has attracted interest as a promising surface enhancement technique due to its ability to induce high pressure shock waves without using a confinement layer. Unlike traditional nanosecond laser peening which introduces compressive residual stresses to depths exceeding 1 mm, fs-LP affects primarily the near-surface region. In this study, we investigate the effects of fs-LP on additively manufactured Scalmalloy (R) produced via laser powder bed fusion (L-PBF). Residual stress characterizations using X-ray, neutron diffraction and finite element modelling reveal compressive stresses extending up to 100 mu m beneath the surface. Crosssectional analysis suggests the formation of a 2-3 mu m nanocrystalline surface layer and evidence of surface oxidation. Hardness increased from 2.53 GPa to 2.62 GPa accompanied by a higher amount of dislocation density. Moreover, fatigue testing demonstrated a similar to 1.6 times improvement in fatigue life which is attributed to delayed crack initiation resulting from the combined effects of surface hardening, residual stress and refined grain structure. These findings highlight the unique capabilities of fs-LP process for targeted post-treatment of critical regions in additively manufactured lightweight alloy components, where conventional peening is impractical or overly aggressive.

Residual stress limits dimensional accuracy and service performance in the Laser-based Directed Energy Deposition (DED-LB) of 316L stainless steel. Process-integrated mitigation was demonstrated using off-axis (oblique-incidence) laser delivery. A 20 mm-thick multilayer build was characterized by neutron diffraction, neutron tomography, electron backscatter diffraction (EBSD), and Vickers macrohardness mapping. Residual stresses were confined to +/- 100 MPa, with interior tension and surface-adjacent compression; neutron tomography measured similar to 0.001% porosity for pores >= 50 mu m. Hardness of 150-230 HV20 colocated with compressive zones, and EBSD showed elongated columnar grains with position-dependent texture. The reduced stress state is attributed to the enlarged projected footprint and lower peak irradiance of off-axis delivery, which spread heat laterally, reduce the thermal gradient ( G ) and cooling rate ( T (center dot) ), and favor conduction-mode melting. These results establish off-axis DED-LB as a route to in situ residual-stress control and microstructural tailoring while maintaining negligible resolved porosity in additively manufactured 316L components. The bulk, through-thickness maps and datasets provide component-scale validation to calibrate models and support process qualification.

Directed Energy Deposition-Arc (DED-Arc) processes create residual stresses in the material due to their nonuniform thermal gradients. These residual stresses interact with the in-service loads and could negatively impact the material integrity. To understand and mitigate the negative effects of these stresses, in this study, a thin-walled structure out of a high strength low alloy (HSLA) steel was manufactured by DED-Arc process. The formation of residual stresses was studied with neutron diffraction at the centerline of the structure. To incorporate the effects of martensitic phase transformation on the residual stress formation, the microstructure of the material was studied using electron and optical microscopy. Also, the phase fractions were calculated using image segmentation methods. Furthermore, thermodynamics calculations were performed to understand the kinetics of the phase changes. The results show that the structure follows a tensile-compressive-tensile-compressive residual stress regime in the travel direction by moving from the lower side of the substrate to the top side of the thin-walled structure. The main influencing factors in the formation of these stresses are the volume expansion due to martensitic and bainitic phase transformations, contraction due to cooling of the hot material, and bending of the structure due to the interaction between tensile and compressive stresses at different heights of the part.

The growing demand for materials capable of withstanding demanding environments has driven interest in compositionally complex alloys (CCAs). Concurrently, cold spray (CS), a solid-state technique that preserves the feedstock microstructure, has emerged as a promising method for depositing CCAs. This work represents the first systematic evaluation of CS processability of a novel mechanically alloyed (MA) Co18Cr24Fe14Ni33V11 CCA powder, developed within the EU Horizon 2020 FORGE project and designed to achieve high hardness. The CS process parameters, including gas temperature, pressure, and nozzle pre-chamber configuration, were systematically studied to achieve an optimal combination of deposition efficiency (DE), thickness per pass, and coating density onto various steel substrates (S700MC, H13, and AISI 310). The results demonstrated that a gas temperature of 1100 degrees C and a pressure of 40 bar, combined with a short pre-chamber, minimised porosity (<0.3%), achieved DE above 30%, and produced coating thicknesses exceeding 40 mu m per pass. Correlation analyses identified temperature as the primary driver of coating quality, with pressure playing a secondary role. The microstructural analysis confirmed the effective transfer of powder microstructure to coating, which exhibited a median microhardness of 729 +/- 63 HV0.1. This high hardness is attributed to the alloy composition, work hardening during mechanical alloying, and severe plastic deformation during deposition - placing it among the hardest CS CCA coatings reported in the open literature. Adhesion strength inversely correlated with substrate hardness, peaking at > 64 +/- 1 MPa on the softer AISI 310 substrates. Neutron diffraction measurements enabled evaluation of through-thickness residual stresses in the coating-substrate system, revealing a predominantly compressive stress state (-142 +/- 27 MPa) within the coating. Interpretation using the analytical model for progressively deposited coatings indicates that the measured stresses arise from the combined effects of deposition-induced peening and thermal misfit between the coating and substrate.

Zinc (Zn) is of increasing interest for applications such as bioresorbable implants and zinc-ion batteries, but use is limited by poor mechanical performance. Equal channel angular pressing (ECAP) offers a potential solution, yet its influence on Zn's crystallographic texture and associated properties including corrosion, dendrite formation, and interfacial behaviours, remains insufficiently understood. This study examines the evolution of microstructure, texture, and slip activity in Zn processed by four standard ECAP routes, referred here as RA, RBA, RBC, and RC. A single ECAP pass produced considerable grain refinement, while further passes gave more limited refining effects and led to route dependent differences in microstructural uniformity and dislocation densities. Severe plastic deformation by ECAP led to broad engagement of basal, prismatic, and pyramidal modes with the contributions from the different modes varying across pressing sequences and between routes. The Y- and B-fibre textures developed in the first pass, while the subsequent textural evolution was strongly influenced by the strain path. RBA and RBC strengthened the Y-fibre at the expense of the B-fibre, in association with 90 degrees billet rotations used for these routes, which led to increased engagement of higher-order pyramidal slip systems to accommodate enhanced c-axis strains. For RC, alternating iso-planar shear imparted by this route led to sustainment of the initially formed Y-fibre dominated texture. Meanwhile, route A distinctively strengthened the B-fibre as 90 degrees intersecting shear planes formed under this strain path promoted continual favourable realignment of input basal planes to the applied shear. Overall, ECAP route strongly influenced the microstructures and textures developed in Zn, which has direct implications for tailoring its performance for biomedical and energy-storage applications.

Determination of the stress-free reference lattice spacing, d_0, is a central and often underestimated difficulty in diffraction-based strain measurement. Although commonly treated as a material constant, d_0 often varies with position and measurement direction as a result of composition, phase, texture and residual stress at the sub-bulk scale. While direct measurement of d_0 from coupons is usually preferable, this is sometimes impractical or even impossible. This paper reviews the d_0 problem in general and develops a hierarchy of non-destructive alternatives based on mechanical equilibrium. This ranges from established techniques based on force-balance, to the application of boundary conditions and finally an approach based on point-wise equilibrium within a sample, implemented through eigenstrain analysis. In all cases, examples are provided in the form of real samples including an additively manufactured Inconel cube, ancient Roman bronze medical probes and an ancient bronze dagger of purported Persian origin. These latter examples demonstrate that equilibrium can provide a practical physical constraint for estimating d_0 when destructive reference measurements are entirely inappropriate.

Transient thermal loads of Wire Arc Additive Manufacturing (WAAM) cause nonuniform plastic deformation, high residual stresses and high delta-ferrite contents that could negatively impact service life, mechanical performance, dimensional accuracy, and result in failure of material during manufacturing. To control these negative effects, it is vital to understand how residual stress and microstructure form during manufacturing. This study, investigates microstructure and residual stress evolutions during WAAM of AISI 316L thin-walled structures, using numerical and experimental methods. The microstructure was analyzed using optical and scanning electron microscopy. Residual stresses were measured with neutron diffraction and numerically simulated by a thermo-mechanical model. The results show that less than 10% of the microstructure consists of inter-dendritic delta-ferrite, which provides relatively high toughness. The material undergoes a ferrite-austenite solidification mode that is preferred for its lower susceptibility to solidification cracking. The material shows a periodic microstructure due to cyclic material deposition, with equiaxed dendrites at the center of each track with low G/ R ratios (6.78 degrees C s/mm2) and columnar and cellular structures close to the bottom and sides of the tracks with significantly high G/R ratios. The highest and lowest residual stresses form perpendicular to the build direction, in the travel and transverse directions, respectively. Residual stresses in the build direction reached 500 MPa in a constrained sample at both ends of the wall, which explains high cracking probabilities in these regions. By changing the WAAM constraint levels, including external clamping and substrate rigidity, residual stress, dimensional accuracy, and failure during production could be controlled.

Additive manufacturing technologies have proven to be an excellent alternative to conventional production methods, especially when geometrically complex parts and low production quantities are aimed at. Specifically, powder bed fusion of metals using a laser beam (PBF-LB/M) additionally allows for the manufacturing of mechanically highly stressable parts. However, the heat input through the laser beam into the material and an irregular cooling during the processing result in the formation of high residual stresses. These lead to form deviations outside the specified tolerances and may accumulate to an extent, at which stress-induced cracking occurs. This emphasizes the need for an accurate prediction of the residual stresses during the PBF-LB/M process with the goal of a first-time-right additive manufacturing. In this study, three specimens exhibiting high residual stress formations during PBF-LB/M were manufactured from the nickel-based superalloy Inconel 718. Afterwards, the stresses were measured by means of neutron diffraction. The results provided the validation data for a subsequent finite element simulation, representing the build-up process on a part-scale, in which the data evaluation was conducted in accordance with the measurements for a high comparability. A comparison between the simulation and the neutron diffraction results of all three specimens showed a very good agreement of the normal stresses in all three coordinate directions, both for tensile and compressive stresses. The obtained results highlight the validity of the applied simplified part-scale simulation. The latter can, therefore, be utilized to increase the process understanding of residual stress and crack formations. It can also be used to enable process parameter modifications or geometry adaptions, aiming at a first-time-right additive manufacturing.

Eutectic high-entropy alloys (EHEAs) feature multiple distinct phases, unlike the single-phase solid solutions typical of conventional high-entropy alloys (HEAs). While EHEAs inherently consist of multiple phases, their performance as thermal spray coatings is directly influenced by their relative phase proportion and microstructural distribution, making phase control crucial for property optimization. While CALPHAD has been used to predict phases in HEAs, there remains a critical gap in its quantitative phase predictive capabilities, particularly for non-equilibrium cooling processes imitated by Scheil simulation. This study investigates Scheil simulation as a tool for both qualitative and quantitative phase prediction in the AlCoCrFeNi2.1 EHEA HVOF (high velocity oxygen fuel) processed coating. The HVOF coating exhibited a deformed zone with unmelted and partially melted regions retaining the eutectic structure of the original powder, as well as a rapid solidified zone displaying a single-phase FCC solid solution. Phase fractions, determined by Rietveld analysis, closely matched those predicted by Scheil simulation - 66.7 wt% FCC and 32.3 wt% B2 versus experimental values of 72.7 +/- 1.1 wt% FCC and 27.3 +/- 1.1 wt% BCC/B2. Furthermore, the coating showed low microhardness and wear resistance, underscoring the limitations of FCC-rich microstructures for tribological applications. These results suggest that Scheil simulations can effectively aid the materials engineering design of EHEA thermal spray coatings.

Accurate and efficient estimation of residual stress and distortion at the design stage remains crucial and challenging, primarily due to the complex and subjective calibrations required by existing modeling methods, hindering their widespread adoption in the additive manufacturing (AM) process. The inherent strain method (ISM) has been widely used due to its proven effectiveness in predicting distortion and for its low computational cost as simulations rely on a single static analysis. Inherent strain is calculated from a meso-scale thermomechanical simulation and applied to a part-scale mechanical simulation, significantly reducing computational time. However, predicting residual stress with conventional ISM requires additional fictious non-physical property modeling, limiting its effectiveness. This study proposes a novel dual-inherent strain method (DISM) for efficient residual stress simulation in additive manufacturing, while retaining the distortion prediction accuracy. The method improves residual stress prediction with a new procedure to calculate and apply strain in part-scale simulations, capturing strain evolution during the AM process without needing calibration in property modeling. The proposed method is validated by experiments conducted on a Ti-6Al-4V double-cantilever beam processed by laser powder bed fusion. Additionally, the proposed approach eliminates the need for calibration of a threshold of fictious non-physical material property used in the conventional ISM, which significantly influences prediction results. On average, the new DISM achieves a 41 % reduction in computational time compared to the conventional ISM. This systematic method is adaptable to different materials and processes without the need for recalibration, making it broadly applicable to various scenarios in additive manufacturing.

Although Residual Stress (RS) induced by Friction Stir Welding (FSW) has been widely investigated for planar weldments, the same attention has not been paid as far as the curved variant is concerned. To comprehensively address this gap, the present paper studies the RS in three AA6082-T6 FSW pipes (37.5 mm outer diameter x 3 mm thickness) manufactured with varying feed speeds, i.e. 50, 75, 100 mm/min. RS evaluations were cross-validated by two independent experimental methods, i.e. Neutron Diffraction and Contour Method. A novel multi-physics Finite Element (FE) model was implemented and calibrated using the previously obtained experimental outcomes to shed light on the key physical mechanism responsible for the arising of RS. The analysis unveiled M-like hoop RS patterns akin to flat FSW butt-welds but having lower magnitudes ranging from -20 MPa to 65 MPa, most likely due to the different thermal histories. The axial RS oscillates between-20 MPa and 20 MPa, whereas the radial component turned out to negligible. The FE model also demonstrated how feed speed, plunge force, and external clamping conditions alter RS magnitude while identifying 75 mm/min as the optimal speed that minimises the peak hoop RS to 40 MPa.

Hetero-interfaces play a crucial role in the deformation behavior and the corresponding mechanical properties of laminated metallic composites. Here, laminated Ti/Zr composites were designed and processed by accumulative roll bonding (ARB) to investigate the role of the miscible/diffusive hetero-interfaces. At the starting of the ARB process, strain localization in terms of shear bands appears, and become predominant with the increasing ARB cycles. The Ti/Zr composites exhibit a significant increment in strength as the roll bonding proceeds, whilst the ductility is not sacrificed substantially. In-situ neutron diffraction during uniaxial tensile loading indicates that the Zr layers are subjected to much higher stress than the Ti layers. The strength of the composite deviates from the rule-of-mixtures, due to the existence of diffusion layers near the hetero-interfaces. These diffusion layers play a dominant strengthening role in the bulk Ti/Zr composites. With the miscible hetero-interfaces, the interactions between the dislocations and the interfaces are weakened, resulting in a marginal role of the heterointerfaces induced strengthening. The load transfer promoted by shear bands in the composites with higher ARB cycles can improve the deformation compatibility between the constituent metals, resulting in satisfactory ductility. These results elucidate the divergent roles of the miscible hetero-interfaces compared to the immiscible counterparts, and provide a new strategy to design high performance laminated metallic composites by artificial interface tailoring.

Inspired by principles observed in nature, bio-inspired welding patterns can be designed to emulate the load-bearing capacity and resilience of natural interlocking structures. This study introduces bio-inspired interlocking weld patterns as alternatives to traditional linear welds, aiming to modify residual stress distribution and examine the effects on static tensile properties. Quasi-static mechanical properties and residual stress of two bio-inspired patterns were assessed and compared to linear welds and base material. Neutron diffraction was used to evaluate residual stresses, while mechanical testing and Finite Element Method (FEM) were employed to evaluate the stress-strain response of the analysed materials. This model generated numerical values for the heat-affected zone (HAZ) properties, enabling the creation of an empirical relationship to predict HAZ extent based on weld geometry. Experimental validation showed strong agreement with the model, and a parametric analysis investigated how weld shape and dimensions influence the joint performance. While the study did not reveal a significant reduction in residual stress magnitudes for the studied geometric configurations, it provided valuable insights into the ways welding patterns can influence stress distribution. Tensile properties were notably affected by the bio-inspired patterns, showing a significant increase in yield strength. An interpretation of these results is also provided.

Zinc (Zn) has potential for applications such as bioresorbable implants but is held back by poor mechanical properties. Equal channel angular pressing (ECAP) enhances mechanical properties by refining the microstructures and can alter crystallographic texture and deformation mechanisms. Here, ECAP of Zn using four standard deformation routes (RA, RBA, RBC and RC-refer to Figure 1 for pressing sequences) was investigated to assess impacts on the microstructure and mechanical properties. Four passes of ECAP reduced the average grain sizes by >50 % and increased yield strengths by up to 80 % compared to the starting material. Varying the deformation route altered the material strain path which impacted microstructure refinement, including uniformity and crystallographic textures. Route A resulted in larger average grain size compared to other routes and there was significant variation of the grain size and hardness across the billet section. Route BC gave most consistent grain refinement and strengthening, while route C had the best processability as it allowed consistent preparation of crack-free billets with a smooth finish. Contrastingly, route BA resulted in heavily cracked billets, while route A led to cracking at the tail of billets. Characteristic crystallographic textures were induced by each route with BA, BC and C exhibiting dominant Y fibre textures, which is associated with ideal shear, oriented according to the material strain path. Meanwhile, less common dominant B fibre texture was formed in billets pressed by route A. The study provides insights to enhance mechanical properties of Zn by ECAP and to influence crystallographic textures which may affect corrosion and biodegradation behaviours.

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Herein, the effect of heat treatment on the characteristics and properties of cold spray additive manufactured 316L stainless steel employing traditional and a new metal knitting strategy is investigated. 316L feedstock powder characteristics, the geometry of the bulk, microstructure, porosity, microhardness, mechanical isotropy, and residual stress are analyzed in both strategies in as‐sprayed and heat‐treated conditions. Results show that the traditional deposition strategy produced higher mechanical resistance, whereas metal knitting presents a better part geometry accuracy. The heat treatment significantly improves the material strength and the quality of the parts by recovery and recrystallization phenomena. The same microhardness and planar isotropy are achieved after heat treatment of samples produced by both strategies. A discussion about the mechanisms, microstructural, and residual stress evolution is presented.

Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg kg(-1) gold), hot, water +/- carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry. However, the widespread occurrence of large gold nuggets is at odds with the dilute nature of these fluids and the chemical inertness of quartz. Quartz is the only abundant piezoelectric mineral on Earth, and the cyclical nature of earthquake activity that drives orogenic gold deposit formation means that quartz crystals in veins will experience thousands of episodes of deviatoric stress. Here we use quartz deformation experiments and piezoelectric modelling to investigate whether piezoelectric discharge from quartz can explain the ubiquitous gold-quartz association and the formation of gold nuggets. We find that stress on quartz crystals can generate enough voltage to electrochemically deposit aqueous gold from solution as well as accumulate gold nanoparticles. Nucleation of gold via piezo-driven reactions is rate-limiting because quartz is an insulator; however, since gold is a conductor, our results show that existing gold grains are the focus of ongoing growth. We suggest this mechanism can help explain the creation of large nuggets and the commonly observed highly interconnected gold networks within quartz vein fractures.

Additive manufacturing techniques, such as laser powder bed fusion (PBF-LB), are well known for their exceptional freedom in part design. However, these techniques are also characterized by the development of large thermal gradients during production and thus residual stress (RS) formation in produced parts. In this context, neutron diffraction enables the non-destructive characterization of the bulk RS distribution. By control of the thermal gradients in the powder-bed plane by scan strategy variation we study the impact of in-process scan strategy variations on the microstructure and the three-dimensional distribution of RS. Microstructural analysis by means of electron backscatter diffraction reveals sharp microstructure transitions at the interfaces ranging from 100-200 mu m. The components of the RS tensor are determined by means of neutron diffraction and the principal stress directions and magnitudes are determined by eigenvalue decomposition. We find that the distribution of RS in the powder-bed plane corresponds to the underlying scan strategy. When the alternating scan vectors align with the x- and y sample coordinate axes, the principal stress directions co-align. In the present geometry, nearly transverse isotropic stress states develop when the scan vectors are either aligned 45 degrees degrees between x and y or continuously rotated by 67 degrees degrees between each layer.

In metal additive manufacturing (MAM), microstructural properties such as texture, residual stresses, and dislocation density have emerged as key factors ruling the resulting mechanical performances. In this study, cylindrical AISI 316L specimens, fabricated with laser powder bed fusion (LPBF), were tested under cyclic elastoplastic (EP) deformation using a constant strain amplitude to highlight the evolution of residual stresses (RS), dislocation density and texture with increasing number of EP cycles, N, across the hardening-softening (H–S) transition stage, in the attempt to find correlations between relevant microstructural parameters and macroscopic properties. The structural and microstructural analysis is carried out through whole powder pattern modeling (WPPM) of neutron diffraction (ND) data and Electron Back-Scattering Diffraction (EBSD) analysis. The H–S transition is found to occur within 7–9 cycles, with RS fading out already after 5 cycles. Across the H–S transition, the trend of the maximum tensile stress correlates closely with the trend of WPPM-calculated total dislocation density, suggesting a major role of dislocations’ characteristics in the evolution of macroscopic mechanical properties. EBSD analysis reveals the rearrangement of geometrically necessary dislocations (GND) into cellular structures, and moderate grain refinement, which are deemed to be responsible for the quick fading of RS in the very early stage of EP loading. ND-based texture analysis reveals a (220) preferential orientation retained throughout the EP tests but with orientation density functions (ODFs) changing non-monotonically with N, suggesting preliminary partial randomization of grains around the deformation axis followed by the recovery of crystallographic anisotropy and more localized ODFs.