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The use of thin films made of alloys, i.e., containing multiple metal species, can enhance their properties. However, as with single-element films, residual stress in the films can limit their performance. A model is proposed for relating the stress in alloy thin films to the processing conditions (growth rate, temperature, and sputter-gas pressure), material properties (composition, atomic and defect mobilities, and elastic moduli), and microstructure (grain size and grain growth kinetics). The model is based on stress-generating processes that occur during film growth at grain boundaries and due to energetic particle impacts. While the equations are similar to those proposed for single-element films, the alloy kinetic parameters now contain the effects of the different atomic species. The model is used to explain the growth rate and composition dependence of in situ stress evolution during the deposition for various concentrations in the tungsten–vanadium system. [ABSTRACT FROM AUTHOR]

The dynamics of residual stress (RS) within glass-to-metal (GTM) seals play a crucial role in their operational efficacy, with the progression of RS in response to temperature variations being a critical aspect in engineering applications. This research utilizes fiber Bragg grating sensors and temperature-calibrated photoluminescence spectroscopy techniques for the in situ monitoring of RS changes within GTM seals during heating. Initially, the glass body exhibited a compressive stress of −203 MPa, while the stress in the glass close to the interface was −367 MPa at room temperature. With increasing temperature, RS within both the glass body and in the glass close to the interface transitions through three distinct phases: a near-linear decrease, a rapid decrease, and a shift from compressive to tensile stress. By 540 °C, tensile stresses of approximately 11 MPa within the glass body and 36 MPa in the glass close to the interface were observed. The study elucidates that RS evolution is intricately linked not only to the thermal expansion properties of the constituent materials but also to the β-relaxation phenomenon within the glass structure and the presence of an oxide layer at the interface. Finite-element analysis simulations were conducted to corroborate the experimental findings, illustrating a congruent RS evolution pattern and delineating the transition from a compressive to a tensile state. This investigation provides empirical data and analytical insights concerning the management of RS in GTM seals, underscoring the significance of RS control in maintaining seal integrity. [ABSTRACT FROM AUTHOR]

We present a method for computing locally varying nonlinear mechanical properties in particle simulations of amorphous solids. Plastic rearrangements outside a probed region are suppressed by introducing an external field that directly penalizes large nonaffine displacements. With increasing strength of the field, plastic deformation can be localized. We characterize the distribution of local plastic yield stresses (residual local stresses to instability) with our approach and assess the correlation of their spatial maps with plastic activity in a model two-dimensional amorphous solid. Our approach reduces artifacts inherent in a previous method known as the "frozen matrix" approach that enforces fully affine deformation and improves the prediction of plastic rearrangements from structural information. [ABSTRACT FROM AUTHOR]

A study of residual mechanical stresses in the surface layer of the HgCdTe/CdTe/ZnTe/GaAs structure based on the registration of the second harmonic signal characteristics of reflected IR laser radiation from the surface of the studied sample passed through a nonlinear crystal was carried out. It is shown that such a sensitive method makes it possible to obtain information about the anisotropy of the polarization of the reflected radiation, caused by the residual deformation. Observations of the fine structure of the angular sweep of the second harmonic signal suggest a complex structure of residual stresses related to the presence of misoriented areas. The results were compared with data obtained from measurements of the azimuthal dependence of the self-reflected second harmonic signal from the sample surface. [ABSTRACT FROM AUTHOR]

Over the last several decades, there has been a lot of research interest in the micro/nano-scale energy harvester, a technology that offers sustainable energy solutions for different micro/nano-electromechanical systems. Investigate various geometries, topologies, and material options for energy receiver designs, as well as interesting nonlinear responses that may be used to push the boundaries of energy receiver design, energy efficiency, and energy density. In the current work, the residual stresses in the system after fabrication, are modeled as the in-plane loading in the system. Although the majority of designs are restricted to MEMS alone, research shows that in-plane loading in the system greatly affects the non-linear vibration of the energy collector and illustrates the potential of increasing its performance by controlling the in-plane load. The impacts of in-plane loading in the MEMS at the microscale tissues were quantified by creating a stress-based piezoelectric-flexoelectric MEMS model and analyzing the non-linear frequency response using a time integrator and a Newtonian iterator. By contrasting them with the outcomes of mathematically modeling the current system and contrasting the outcomes of the current technique with the outcomes of the earlier study, the findings in a Python environment known as the XGBoost methodology are re-validated. This strategy is founded on the concept of "reinforcement," which integrates many training methodologies with the detection of underperforming individuals to cultivate proficient learners. Finally, numerous suggestions for raising the nonlinear vibration of the energy harvester are carefully considered. [ABSTRACT FROM AUTHOR]

This paper proposes a numerical approach for predicting residual stresses induced during the additive manufacturing (AM) of polymer composites and their effect on the deformation behavior of the composites. A finite element (FE) model was developed on Abaqus/Standard for 3D printing of layered polymer composite using three polymers: HDPE, PVC, and ABS. The material properties of pure polymers and their blends were measured through tensile testing of injection-molded specimens. These properties were then used as input data in the FE model for the regions of pure polymers and their interfaces. An uncoupled thermo-mechanical analysis was performed, where a heat transfer analysis was realized first using elements birth (activation/deactivation) technique and a moving cylindrical volumetric heat source as a Fortran subroutine (DFLUX). With temperature input from thermal simulation, a mechanical analysis was carried out to deform the polymer composites along and across the print direction, i.e. under isostrain and isostress conditions, respectively. It was observed that the theoretical models existing in the literature underestimate the material properties as they do not consider the residual stresses developed during fabrication. The FE simulations predicted that the estimated material properties were 10 to 50% different from those calculated by the theoretical models, depending upon the residual stress level and the print direction. [ABSTRACT FROM AUTHOR]

In the present exploration, the role of surface stress tensor as one of the most important size effects at nanoscale in the nonlinear dynamical behavior of nanoplate-type energy piezo-harvesters under a time-dependent mechanical actuation is investigated. The general form of the energy functional associated with a quasi-3D nanosize energy piezo-harvester incorporating the surface Lame constants and the residual surface stress is derived. After that, by taking the Hamilton's principle into consideration, the weak form of the surface continuum mechanics-based governing equations for a nanoplate-type energy piezo-harvester is achieved. Afterwards, the meshless collocation strategy is utilized to numerically solve the established coupled electromechanical surface elastic-based nonlinear problem with the aid of implementing a combined form of the polynomial-kind and radial-kind basis functions to eliminate any singularity which may be observed for the associated moment matrices. One can find that for the nanoplate-type energy piezo-harvesters under simply edge supports owning the thickness of 10 , 20 , and 50 nm , the average value of the achieved voltages are equal to 84.7140 , 169.4280 , and 423.5701 μ v , respectively. However, by taking the role of surface stress tensor into consideration, these values in order reduce to 48.7650 μ v (− 42.44 %) , 126.8687 μv (− 25.12 %) , and 386.3565 μv (− 8.79 %). Moreover, for the nanoplate-type energy piezo-harvesters under clamped edge supports owning the thickness of 10 , 20 , and 50 nm , the conventional average values of the attained voltages are, respectively, 71.9994 , 143.9989 , and 359.9973 μv. However, by taking the role of surface stress tensor into consideration, these values in order decrease to 27.1823 μv (− 62.25 %) , 83.0573 μv (− 42.32 %) , and 328.9342 μv (− 8.63 %) , respectively. Therefore, it is deduced that the role of surface stress tensor in the nonlinear dynamical behavior of nanoplate-type energy piezo-harvesters owing lower thickness is more prominent. [ABSTRACT FROM AUTHOR]

This work proposes a topology optimization method for continuous fiber-reinforced composite (CFRC) structures with additive manufacturing (AM), which realizes the concurrent optimization of material layout and fiber orientation. The residual stress caused by AM process is constrained to avoid the failure of warpage and distortion. The inherent strain method (ISM) is applied to simplify the calculation of residual stress, the Tsai–Wu criterion and P-norm are incorporated to realize structural failure prediction and local constraint aggregation. Several typical instances are adopted to verify the effectiveness of proposed method, which provides a novel solution for the optimization of CFRC structures fabricated by AM. [ABSTRACT FROM AUTHOR]

This study investigates the impact of cutting parameters on residual stress in components made from AA7075 material, which were hot forged and subsequently subjected to T6 heat treatment. Using the Taguchi experimental design, two distinct cutting cases—face turning and circumferential turning—were devised to assess residual stress at different sections of the part. During the turning process, force measurements were conducted with a dynamometer, and residual stress was subsequently measured using the X-ray diffraction method. The results indicate that both mechanical and thermal loadings significantly influence residual stress. Notably, spindle speed has the most substantial effect on residual stress in both face turning and circumferential turning, with an observed increase of up to 30% and 20%, respectively, in tensile residual stress for Case 1 and Case 2. When thermal loads are predominant, residual stress tends to be tensile, with measurements reaching as high as 89 MPa. [ABSTRACT FROM AUTHOR]

Cold radial forging (CRF) is recognized as one of the most effective manufacturing processes for the production of hollow components. Nonetheless, even minor alterations in the alloy composition during the cold deformation processing phase can significantly influence the material's manufacturability. This study addresses the challenges associated with high optimization costs, complex data acquisition, and the prediction of forming quality when integrating multiple processes, such as heat treatment and material composition. We propose the development of an intelligent predictive model aimed at forecasting the forming quality of the 20CrMnTiH alloy during CRF, utilizing a back-propagation neural network optimized by genetic algorithm (GA-BP). The assessment of forming quality is based on parameters such as damage, residual stress, and equivalent strain. The study investigates the impact of alloy composition and spheroidal annealing (SA) process parameters on forming quality. The performance of the three GA-BP prediction models is superior in terms of the coefficient of determination (R2) and mean square error (MSE), when compared to a conventional BP neural network and four other machine learning techniques, including gradient-boosted decision trees, random forests, support vector regression, and logistic regression. A comprehensive comparative analysis of the evaluation metrics across all three prediction models, alongside multi-objective optimization, indicates that the Pareto solution set generated by NSGA-II exhibits optimal distribution uniformity. The optimized process parameters (0.17%C-0.24%Si-0.81%Mn-0.03%P-0.03%S-1.15%Cr-0.05%Ni-0.06%Ti, Te: 60℃, ATi: 4.57 h) resulted in a reduction of residual stresses by 12%, equivalent strain by 15%, and component damage by 30%. The results demonstrate that the methodology proposed in this paper not only enhances the quality of CRF molding but also significantly improves the accuracy of the predictive model for forming quality. [ABSTRACT FROM AUTHOR]

The longevity of solid oxide fuel cells is influenced by internal residual stresses, which may induce deformation or fracturing of components. This study investigates the residual stress distribution at the nonplanar cathode–electrolyte interface by approximating the actual interface with trigonometric functions and developing a three-dimensional (3D) model. The model reveals that the stress patterns at nonplanar interfaces can elucidate the genesis of interfacial cracks. During fabrication, anode contraction results in compressive stress within the electrolyte and tensile stress within the anode, with thermal discrepancies between layers being the primary cause of residual stresses. The reduction process diminishes these stresses, thus enhancing the mechanical integrity of the cell. Mitigating interface nonplanarity is beneficial for minimizing residual stress. At each interface crest, the electrolyte exhibits a local minimum in compressive stress, and a local maximum in shear stress occurs between each crest and trough. Furthermore, decreasing the initial porosity and NiO volume fraction can slightly lessen interlayer thermal discrepancies, with little effect on residual stresses. [ABSTRACT FROM AUTHOR]

In this study, an optimum process parameter space is proposed by comparing autoclave, oven curing and vacuum infusion process of manufacturing of GFRP composites. The process parameters, such as the degassing time of resin‐hardener mix, single or double vacuum bagging (DVB), fiber volume fraction and condition of the vacuum pump (VP) were considered. The novelty of the study shows that a VP Off and 5 min degassing condition exhibited 27%, 18% and 27% increase in tensile modulus, tensile strength and interlaminar shear strength as compared to the other methods. The normalized tensile strength, on the other hand, was comparable with DVB, oven and autoclave curing. A magnitude of 1.5 MPa of residual stress was measured with the help of x‐ray diffraction (XRD). This was verified by a Raman Spectroscopy, which showed a residual strain of 0.2% at a spectral peak of 1186 cm−1. The proposed methodology would assist the industries in choosing the right combination of process parameters required for a targeted tensile and interlaminar performance. Highlights: Effect of out‐of‐autoclave and autoclave processes on the performance of GFRP was studied.Degassing time, vacuum bagging and Vacuum pump conditions were investigated.Vacuum pump Off and 5 min degassing time were found to be optimal.Tensile and Interlaminar shear strength were improved by 18% and 27% at optimal condition. [ABSTRACT FROM AUTHOR]

This paper examines the performance and failure mechanisms of atmospheric plasma sprayed (Gd, Yb)-doped YSZ (RYSZ) thermal barrier coatings (TBCs) under oxy-acetylene flame thermal shock conditions. The study involved cyclic thermal shock testing at temperatures of 1400 °C, 1500 °C, and 1600 °C for 10-min intervals until failure occurred, with failure counts recorded as 6, 2, and 2, respectively. During the thermal shock tests, tensile stress in the top coat (TC) caused vertical cracks. The growth of the thermally grown oxide (TGO) layer concentrated stress at the top coat/bond coat interface, leading to transverse interfacial cracks. As the shock temperature increased, the density of vertical cracks and the length of transverse interfacial cracks also increased. Additionally, transverse cracks developed in the TC due to sintering of the surface region at higher shock temperatures. The interaction between vertical and transverse cracks was critical to the spalling of the TC. Variations in crack densities and lengths resulted in different failure modes of the TBCs, depending on the thermal shock temperatures (1400 °C, 1500 °C, and 1600 °C). [ABSTRACT FROM AUTHOR]

Silicon nitride ceramic (Si 3 N 4) for industrial applications is conventionally manufactured with sintering additives, and the properties of Si 3 N 4 change significantly based on the contents of these additives. In this study, we investigate the effects of laser shock peening (LSP) on Si 3 N 4 sintered with varying ratios of sintering additives. The Si 3 N 4 samples were sintered with a mixture of Y 2 O 3 , MgO, and SiO 2 sintering additives at 5, 7, 9, and 11 wt%. A Nd:YAG laser (wavelength = 532 nm, maximum pulse energy = 1.4 J, repetition rate = 10 Hz, pulse duration = 8 ns, beam diameter = 11 mm, top-hat profile) was used to irradiate the Si 3 N 4 samples. The samples were coated with a protective layer (100 μm thick aluminum foil) and a water layer to confine plasma. LSP of Si 3 N 4 with 5 % sintering additives resulted in a slight change in surface hardness but a 77 % decrease in surface compressive residual stress. In contrast, LSP of Si 3 N 4 with 11 % sintering additives led to a simultaneous increase in surface hardness (7.3 %) and surface compressive residual stress (67 %), indicating a significant difference in the effectiveness of LSP depending on the ratio of sintering additives. Additionally, the surface of Si 3 N 4 with 11 % sintering additives showed evidence of grain refinement after LSP. It was demonstrated that the bending strength of Si 3 N 4 with 11 % sintering additives increased by 15.2 %, and the depth of the fracture origin was significantly deepened. [ABSTRACT FROM AUTHOR]

In this study, we compare the residual stress state in a laser powder bed fusion (PBF‐LB/M) AlSi10Mg alloy in the as‐built (AB) condition with that after two different heat treatments (265 °C for 1 h, HT1; and 300 °C for 2 h, HT2). The bulk residual stress (RS) is determined using synchrotron X‐ray diffraction (SXRD), and near‐surface profiles are determined using laboratory energy‐dispersive X‐ray diffraction (EDXRD). The EDXRD results do not reveal any notable difference between the conditions at a depth of 350 μm, suggesting that the machining process yields a comparable residual stress state in the near‐surface regions. On the other hand, the SXRD results show that HT1 is more effective in relieving the bulk RS. It is observed that HT1 reduces the RS state in both the aluminium matrix and the silicon network. In addtion, HT2 does not have a significant impact on relaxing the RS as‐built state of the matrix, although it does induce a reduction in the RS magnitudes of the Si phase. It is concluded that the heat treatment stress relieving is effective as long as the Si‐network is not disaggregated. [ABSTRACT FROM AUTHOR]

The mechanical stress improvement process (MSIP) is a crucial technique employed in nuclear power plants to enhance the reliability and safety of piping systems, which are susceptible to stress corrosion cracking. This study aims to address the significant challenge of preventing such failures by effectively eliminating residual tensile stresses present in weldments. By mitigating these stresses, MSIP helps prevent the formation of new cracks and slows the progression of existing ones in piping systems. This approach induces beneficial compressive stresses along the inner surface of the pipe near the weld, including the molten and heat-affected zones. Multiple cases were analyzed through numerical simulations to assess the efficacy of MSIP in reducing stress concentrations and enhancing structural integrity. Furthermore, the dimensions and placement of the MSIP tool were evaluated, revealing that the optimal position and width of the clamp are 30 mm from the weld line (WL) and 75 mm, respectively. The results indicate that the WL region experiences significantly high compressive stresses, which gradually decrease within a 10-mm distance on each side of the WL. This research contributes valuable insights into the application of MSIP in improving the durability and safety of nuclear piping systems. [ABSTRACT FROM AUTHOR]

Silicon nitride (Si3N4) is widely used in multiple fields due to excellent properties. However, the improvement of the mechanical properties by the existing processing is limited, and the surface modification mechanism of the material is not enough. Therefore, laser-assisted grinding (LAG), combing laser heating with grinding, is proposed. The LAG process is simulated by molecular dynamics (MD) simulation, and the Si3N4 grinding force, atom removal, damage mechanism, and residual stress are investigated. The machining surface hardness arrives at 1862.6 HV, higher than traditional grinding (TG). The grinding force and surface roughness are reduced by 53% and 25.6%, respectively. The study results promote high-performance fabrication of substrate surfaces while filling up the study of Si3N4 matrix removal and damage. [ABSTRACT FROM AUTHOR]

Ultrasonic elliptical vibration cutting (UEVC) has the advantage of extending the tool life and improving the surface finish, which can realize the precision machining of hard and brittle tungsten heavy alloys (WHAs). Combined with finite element simulation and cutting experiments, this paper studies the effect of two-phase amplitude on the stress, strain, surface morphology, and residual stress distribution of the machined surface of WHAs by UEVC and draws the following conclusions: the material removal mode of WHAs in UEVC is the "Compression-Shear-Tension" composite process, and the tool cuts into the workpiece through extrusion and then forms chips through shearing and pulling. The variation of the two-phase amplitude causes the surface morphology and plastic deformation of the machined surface to exhibit up and down fluctuations, while the surface residual stress shows an alternating distribution of tensile and compressive stress, and the tensile stress is mostly distributed on the surface bulge. Increasing the amplitude Aa along the cutting direction promotes the flatness and deformation homogeneity of the surface, effectively reducing the residual tensile stress. Increasing the amplitude Ab along the cutting depth direction reduces the surface residual tensile stress but leads to the roughening and inhomogeneous deformation of the machined surface. Therefore, from the point of view of reducing the surface roughness and improving the fatigue life, the large Aa should be selected in UEVC of WHAs. In order to suppress the deterioration of the machined surface mass as large Ab is applied, it is necessary to ensure that Aa is larger than Ab. [ABSTRACT FROM AUTHOR]

Residual stresses and shakedown have been successfully presented by two‐dimensional numerical experiments based on the discrete element method (DEM), wherein a cohesionless‐frictional material under moving surface loads was replicated through irregular‐shaped particles. With surface loads below the shakedown limit, both permanent deformations and residual stresses cease to accumulate and the numerical structure shakes down after a number of load passes. Corresponding micro‐mechanical analyses indicate that strong forces and normal forces make a dominant contribution to residual stresses. Besides, averaged magnitudes of interparticle forces and corresponding total contact numbers initially change with load passes, and their final variation trends will differ as the structure shakes down or not. Furthermore, polar distributions of interparticle forces and contacts have been presented, and variations of their preferential orientations were emphasised. Lastly, the fabric tensor and anisotropy of resultant forces were studied, presenting the anisotropy weakening of macro‐stress fields, induced by developments of residual stresses. [ABSTRACT FROM AUTHOR]

Shot peening (SP) and fine particle peening (FPP) were performed as post‐treatments on induction‐hardened and tempered AISI 4140 steels. Furthermore, the combined effects of surface characteristics including changes in surface morphology, compressive residual stress, and hardness on the fatigue limit were quantitatively examined. The surface characteristics of the prepared specimens were investigated using a laser and stereomicroscope, a micro‐Vickers hardness tester, and an X‐ray device for residual stress measurements. The rotating bending fatigue properties were also examined. FPP increased the fatigue limit of induction‐hardened and tempered steel samples by introducing compressive residual stress and increasing their surface hardness. Conversely, the fatigue limit of the steel treated with SP was lower than that of the electrochemically polished sample owing to the formation of large dents. The fatigue limits of post‐peened induction‐hardened and tempered steels can be estimated using a modified Goodman diagram considering changes in surface properties. [ABSTRACT FROM AUTHOR]

The effects of vibratory peening (VP), shot peening (SP), and SP followed by vibratory finishing (SPVF) on the surface and fatigue properties of Ti‐6Al‐4 V were compared to conventional low‐stress grinding (LSG). VP processing produced seven times smoother surface finish than SP and 66% deeper compressive residual stresses (CRS) but with 12% lower magnitudes. SPVF produced optimal surface properties with a perfectly flat surface and CRS‐like SP. All three mechanical surface treatments generated similar fatigue life improvements (108–122%) over LSG when the cyclic stress was below the yield stress. Above the yield stress, most of the CRS relaxed during the first cycle in VP specimens, resulting in up to 97% fatigue life improvement over LSG. The CRS relaxed more gradually in SP specimens leading to larger (up to 239%) fatigue life improvement. This shows the need to amplify CRS magnitudes produced in VP to maximize fatigue life improvement. Highlights: Vibratory peening (VP) provides 7X better surface finish than shot peening (SP).VP generates 66% deeper compressive residual stresses (CRS) compared to SP.VP increases fatigue life up to 122% relative to low‐stress grinding.SP generates higher CRS and longer fatigue life above the yield stress than VP. [ABSTRACT FROM AUTHOR]

Nature offers a valuable source of inspiration when designing optimized structures. For instance, when two or more shells are joined during growth processes, Nature prefers to exploit interlocking paradigms to enhance the strength of the bond—cranial sutures are one example. Mimicking this distinctive characteristic when welding thin metallic elements may offer some structural benefits. The present study theoretically investigates the possibility of mitigating the detrimental tensile residual stress that always originated by welding processes, by exploiting Computational Welding Mechanics. Specifically, two plates joined by laser welding following sinusoidal paths (i.e., wave‐like), alongside a linear one, will be studied and compared. Thanks to the distinctive temporal and spatial heat distributions of sinusoidal welding, both welding stress and strain develop in dissimilar ways compared with linear path welding—this is reflected to the resulting weldment distortion too. The results show that geometrically optimized sinusoidal welding can effectively reduce residual stress magnitudes compared with the linear configuration counterpart. The implications of these findings are of particular interest when dealing with the structural performance of welded structures, especially in fatigue contexts. Highlights: The effect of sinusoidal path welding on residual stress is investigated.The welding path significantly modifies the thermal history of the weld bead.Sinusoidal path welding offers an effective capability of tuning residual stresses. [ABSTRACT FROM AUTHOR]

The high‐temperature fretting fatigue damage characteristics of dovetail specimens strengthened by nanosecond laser (NL) and nanosecond combined femtosecond laser (F‐NL) were investigated. The results show that the fretting fatigue life of the NL strengthened sample (NL sample) is improved by 211.2% compared to the base metal samples (BM sample). The lifetime of the nanosecond combined femtosecond strengthened sample (F‐NL sample) was increased by 319.6%. It was attributed to the strengthening introducing hardened layers, residual compressive stress field, and high density of dislocations. The combined strengthening process reduces the surface roughness of the NL strengthened surfaces, while the strengthening influence layer is further increased. The fracture morphology shows that the crack source of the strengthened specimen has changed from multi‐source sprouting to single‐source sprouting, and the crack source sprouted on the subsurface. The fatigue strip morphology similarly confirms that a reduction in the crack propagation rate occurs. Highlights: Dovetail specimens were subjected to fretting fatigue testing at 500°C.Composite laser peening reduces surface roughness and stress concentrations.Mechanism of fatigue property enhancement after combined laser peening revealed. [ABSTRACT FROM AUTHOR]

This study explored the impact of microstructure and residual stresses on the fracture behavior of as‐deposited thermal barrier coatings (TBCs). Two distinct air plasma sprayed TBCs, Coating A (conventional lamellar porous) and Coating B (dense vertically cracked), were investigated. Coating A involved coarser but less dense powders as feedstock and a lower substrate temperature during deposition. Further, Coating A had ∼2.5$\sim 2.5$ times higher randomly oriented porosities, finer grains, lower hardness, and elastic stiffness. Strikingly, however, the fracture strength was higher for the porous as‐deposited Coating A. The answer to this apparent contradiction emerged from the intergranular residual stresses. These were measured using both X‐ray diffraction and high‐resolution‐electron backscattered diffraction. Coating B, deposited at a higher substrate temperature, had clear growth selection of (102)$({1\ 0\ 2})$ oriented grains. These also had more out‐of‐plane normal and shear residual stresses. The growth selection induced residual stresses appeared responsible for the decohesion of Coating B from the substrate and, correspondingly, lower fracture strength. [ABSTRACT FROM AUTHOR]

By means of laser shock peening (LSP) for 1–6 times, microstructure observation, hardness, rotating bending fatigue performance tests, and the influence of the absorption layer on the LSP effect of the M50 steel has been studied. The results show that, after LSP with an absorption layer of aluminum foil or black tape, carbide fracture and pit damage occurred on the surface of the sample, and the damage degree gradually increased with the increase of shock times. The hardness was increased by 9.3% and 7.8%, and the residual stress was increased by 37.5% and 36.1%, respectively. The rotating bending fatigue limit strength of the steel increased by 45.9% and 44.5%. LSP effectively improves the fatigue performance of steel. [ABSTRACT FROM AUTHOR]

Direct bonding is an attractive technique to join material components without the use of intermediate adhesive medium. Usually, the bonding interface can experience high level of residual stress concentration due to entrapped nano-scale particulate contamination. Existing theoretical models are not capable of analyzing such residual stress concentration, since they fail to consider the localized material inhomogeneity formed between the bonding pairs as result of thermal and diffusion processes. This paper proposes a new theoretical model to analyze the residual stress concentration in the bonding interface with the consideration of localized material inhomogeneity. Following the idea of Selvadurai and Singh (Int. J. Fract. 25:69–77, 1984), the nano-scaled particulate contamination induced interfacial defect is simulated as a penny-shaped crack indented by a smooth rigid disc inclusion. This mode I crack-inclusion model is interpreted as a three-part mixed boundary value problem in the theory of elasticity, which is solved by a series expansion technique. Mathematical difficulties associated with modelling arbitrary localized material inhomogeneity are overcome by the use of the General Kelvin Solution (GKS) based method. Exact analytical solutions for the stress intensity factors (SIFs) and resultant force on the inclusion are obtained. Our results show that the inclusion-crack radius ratio and the localized material inhomogeneity can have significance effect on the residual stress concentration at the bonding interface. [ABSTRACT FROM AUTHOR]

This study focuses on the influence of synergistic control of process parameter selection during the preparation of 45 pct Vol. carbon fiber-reinforced aluminum matrix (CF/Al) composites on the quality and properties of the composites. Effects of key process parameters—pouring temperature, preheating temperature, and infiltration pressure—on infiltration saturation (λ, pct) of CF/Al composites were systematically investigated via orthogonal experimental design. Through data fitting analysis, a regression model for λ was successfully constructed, revealing matching law and optimal combination of process parameters. The results show that preheating temperature has the most significant effect on λ, followed by pouring temperature, while the effect of infiltration pressure is relatively small. The optimized parameters are preheating temperature of 558.78 °C, pouring temperature of 747.11 °C, and infiltration pressure of 48.22 MPa, under which λ reaches 97 pct and tensile strength is 195 ± 6.6 MPa. Additionally, regions with different λ can be intuitively differentiated by plotting forming process maps. Finally, interfacial thermal residual stress minimizes when interfacial layer thickness is about 1 μm. This study provides an important basis for optimizing CF/Al composite preparation process. [ABSTRACT FROM AUTHOR]

Martensite and bainite are formed from austenite through the rapid application of Bain's strain. In several studies, martensite is considered as a body-centered tetragonal phase, but it can also be viewed as bcc ferrite supersaturated with carbon, subject to internal residual stresses from incomplete relaxation of Bain's strain. Recent electron backscatter diffraction measurements have revealed a broad spectrum of tetragonality in quenched martensite, which can be attributed to the diversity of internal stress rather than variations in carbon distribution. Therefore, a thermodynamic unit cell model is developed to calculate the kinetics of carbon atom occupancy in particular kinds of octahedral interstitial lattice sites, contributing to tetragonality in loaded ferrite. The model includes a Zener-ordering term that influences carbon atom distribution and consequently affects tetragonality. Simulations suggest that carbon redistribution among octahedral interstitial lattice sites reaches equilibrium with internal stress within an hour at room temperature. The presented model provides a framework for understanding tetragonality in martensite and bainite, incorporating the effects of internal stress and carbon atom distribution in particular kinds of octahedral interstitial lattice sites. [ABSTRACT FROM AUTHOR]

Managing the hardness, density, and residual stress of the titanium nitride (TiN) hard mask has become increasingly significant for achieving excellent selectivity in the high aspect ratio etching process. This research investigates the enhancement of hardness, density, residual stress, and etch selectivity of a TiN film during the atomic layer deposition process using varying NH3 flow rates. Additionally, the study establishes a correlation between the improvement of hard mask properties and NH3 flow rates, taking into account the film composition, crystallinity, surface roughness, interface layers, and film thickness. The effects of NH3 could be summarized into three types. High N–N and Ti–N bonds, along with increased film hardness, are achieved by elevating the NH3 flow rate. Furthermore, this adjustment promotes the growth of crystal planes with higher lattice constants and modifies the interface layer thickness between Si and TiN, directly impacting residual stress. The TiN film exhibits increased roughness and decreased uniformity. In addition, at NH3 50 SCCM, hardness, density, and residual stress improved by 81.8%, 110%, and 87.5%, respectively. The selectivity saw a significant increase of 77.7%. This study provides an analysis of the relationship between the NH3 flow rate and TiN thin film properties, which is essential for improving TiN hard mask properties in flow type reactors. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSThe growth mechanism and kinetic characteristics of SiC whiskers for novel bionic ceramic cutting tools were analyzed by modified Arrhenius equation, which reveals the regulation effect of SiC whisker growth on the microstructure evolution. Furthermore, the influence of the growth mechanism on the toughening mechanism under shear and indentation failure was investigated. The results showed that the formed transition area at the bonding interface can improve the residual thermal stress distribution. The synergistic effect of multiple macro/micro-toughening mechanisms and interfacial strengthening mechanisms enabled the bionic ceramic cutting tool materials to exhibit excellent fracture resistance under shear and indentation failure.Analyze growth behavior and kinetics of SiC whiskers by the modified Arrhenius equation.Toughening mechanisms taking into account growth kinetics of SiC whiskers.Multiple macro- and micro-toughening mechanisms enhance the fracture resistance. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti6Al4V is extensively utilized in biomedical applications due to its excellent biocompatibility, corrosion resistance, and mechanical properties. The design of dental implant surface textures has changed throughout time to address issues with oral rehabilitation in both healthy and damaged bones. The longevity of an implant is significantly impacted by surface roughness. This study examines the use of laser shock peening (LSP) as a surface modification technique to improve the mechanical properties of implants. A numerical model is developed using the commercial finite elements software in ABAQUS/Explicit for simulating dynamic conditions. The aim of the study is to develop surface roughness parameters using computational methods such as studies have not yet been contemplated. The single shot angle, shot repeat, time, material orientation, and laser power are applied for the first time simultaneously to evaluate the impact of material orientation and loading angles on surface roughness parameters. The study showed that the developed computational model's compressive residual stress was −578.45 MPa, while the experimental samples were −592.18 MPa. Consequently, the difference between the computational and experimental results was 2.32%. Without regard to material orientation or angle, the compressive residual stress of the samples under examination was found to be −578.450 MPa after three repetitions and to decreased to −1.620 MPa after four. These results demonstrate that by varying the material orientation and loading angle, the Ra value may be increased four times. [ABSTRACT FROM AUTHOR]

High‐speed dry milling (HSDM) technology is one of the most attractive solutions for improving the cutting performance of difficult‐to‐machine materials. However, the study of HSDM performance for 30CrMnSiNi2A steel has not been reported. In this article, HSDM for 30CrMnSiNi2A steel is investigated using TiN‐coated and AlTiN‐coated tools, focusing on cutting force, vibration, surface roughness, residual stress, and tool wear. The effects of cutting parameters on cutting force and vibration are remarkably similar. At a spindle speed of 7500 r min−1, both cutting force and vibration are minimized. TiN‐coated and AlTiN‐coated tools exhibit distinct performance differences. But, HSDM of 30CrMnSiNi2A steel using TiN‐coated and AlTiN‐coated tools can achieve low surface roughness. The depth of cut significantly affects surface roughness, which is lowest at the depth of cut (0.8 mm). Most of the workpiece surface shows residual compressive stress. The main wear mechanisms for both coated tools are abrasive wear, adhesive wear, and oxidative wear. Furthermore, the AlTiN‐coated tool is more wear resistant on the flank face compared to the TiN‐coated tool. Chipping due to crater wear is the leading cause of tool failure for the AlTiN‐coated tool. Upon various comparisons, the AlTiN‐coated tool is more suitable for HSDM of 30CrMnSiNi2A steel. [ABSTRACT FROM AUTHOR]

The phenomenon of hydrogen trapping in precipitates of steels is well-recognized, though a precise atomic level understanding remain elusive, leading to ongoing debates. This study highlights the specific roles of interfaces under various coherent conditions through first-principle calculations, incorporating local stress level, which is a novel aspect seldom explored in previous studies. It was found that coherent interfaces exhibit varying hydrogen-trapping capacities depending on their defect states, with the lowest hydrogen solution energy reaching −0.83 eV, primarily functioning as reversible traps. In contrast, derivative interfaces demonstrate superior hydrogen-trapping capacity, with hydrogen solution energy reaching −1.28 eV, classifying them as irreversible sites. Specific tensile or compressive stresses do not necessarily enhance the entrapment or release of hydrogen at precipitate interfaces; instead this depends on the characteristics of polyhedral interstices within the interfaces, with residual stress from hydrogen segregation also playing a critical role. These findings help address certain apparent controversies and advance understanding of the hydrogen embrittlement mechanism. Comprehensive investigation of H trapping characteristics of precipitates with various coherent conditions under stress. [Display omitted] • Perfect coherent precipitates exhibit very limited H-trapping capacity. • Coherent interfaces with Es reaching −0.83 eV mainly serve as reversible traps. • Derivative interfaces with Es reaching −1.28 eV function as irreversible traps. • Various stress levels can enhance H entrapment or release at precipitate interfaces. [ABSTRACT FROM AUTHOR]

The AA2219 is an Al-Cu alloy with widespread engineering applications. The sheet parts of this alloy are produced by metal forming and are subjected to age hardening (e.g., T6 temper) for strengthening. The cold work in metal forming affects the ageing behavior of alloy and hence the resulting mechanical properties. In this research, a novel forming technique namely Incremental Forming with three different forming-ageing routes is employed to produce age-hardened AA2219 parts. The resulting microstructure evolution, mechanical properties, and residual stresses are examined. The results reveal that forming imposed cold work (35% plastic strain) enhances the sheet strength and hardness to a certain extent, which can be further enhanced by opting an optimum forming-ageing route. Similarly, the residual stresses also show sensitivity to the forming-ageing route opted. Based upon extensive analysis of the experimental results, it is concluded that the [O-IF-ST-T6] route is the most appropriate route for producing age-hardened parts with high strength, hardness and ductility, and low residual stresses (where O, IF, ST, and T6 represent parent, incremental forming, solution treatment and T6 ageing, respectively). This route is found to offer a gain of 238% in the tensile yield strength, 151% in the ultimate tensile strength, and 200% in the hardness with respect to the parent metal. Further, from several correlations drawn between mechanical properties and microstructural quantities, namely grain size, and precipitate's size and density, strengthening mechanism is revealed for the reported gains. [ABSTRACT FROM AUTHOR]

Reducing non‐radiative recombination caused by defects at buried interfaces is crucial to the development of efficient and stable perovskite solar cells (PSCs). Herein, supramolecular cucurbit[5]uril (CB[5]) is introduced into the SnO2 layer, where it engages in host–guest interactions to suppress oxygen vacancies in SnO2, prevent particle aggregation, and enhance the electron mobility of SnO2. By serving as a bridging agent at the buried interface between SnO2 and the perovskite layer, CB[5] reduces the defect density and improves the carrier extraction efficiency. It also enhanced the surface energy of the SnO2 substrate, facilitates the formation of large grains in the perovskite film, alleviates residual lattice stresses, and enhances the film quality. Consequently, the PSC with CB[5] shows a champion power conversion efficiency of 24.83%. Moreover, an unencapsulated device incorporating CB[5] retains more than 87% of its initial PCE under continuous illumination at the maximum power point tracking for 1000 h. This study pioneers the utilization of cucurbiturils in PSCs and provides insights into how supramolecular compounds can regulate buried interfaces. [ABSTRACT FROM AUTHOR]

Ni-based composite coatings containing transition metal carbides exhibit high hardness, and the rapid heating and cooling characteristics of laser cladding lead to the formation of cracks in these coatings, significantly limiting their practical industrial applications. In this study, (Ti, V)C/Ni composite coatings were prepared at different preheating temperatures to investigate the effect of preheating on crack formation. The microstructure of the coatings was investigated by XRD, OM, and SEM, and the differences in wear resistance were studied by block-on-ring wear tests. The results show that with increasing preheating temperature, the residual stress in the coatings decreases significantly, the secondary dendrite arm spacing increases, and the number of cracks decreases. No crack defects were observed in the coating preheated at 700∘C, indicating that substrate preheating can effectively suppress crack formation during the laser cladding process. Compared with the coating prepared without preheating, the hardness and wear resistance of the coating prepared by preheating at 700∘C were reduced, which was still 5.6% higher than that of the substrate after quenching, and the wear resistance was 1.76 times higher than that of the substrate. [ABSTRACT FROM AUTHOR]

To alleviate residual stress of ZrO 2 /GH536 brazed joints, the micro-scale structures were fabricated on ZrO 2 via selective laser melting technology before its vacuum brazing with GH536 superalloy. The effects of micro-scale structures on the interfacial microstructure and residual stress of brazed joints were studied. The characterization results indicated that due to its reaction with excessive Ti elements from filler, the micro-scale structures prevented the detrimental effect of over-thick brittle reaction layer on the mechanical properties of joints. Furthermore, the Invar effect of the micro-scale structures facilitated the transfer of residual stress from the ceramic side to the micro-scale structures. According to the numerical simulation results, the maximum residual stress in the brazed joint with micro-scale structures decreased from 622 MPa to 310 MPa. As a result, the fracture path was changed from the flat shape to zigzag. This work reveals the stress-relaxed mechanism of micro-scale structures and provides a new method for fabricating the ceramic/metal joints with low residual stress. [ABSTRACT FROM AUTHOR]

This study examines the impact of the bonding temperature parameter on the quality of diffusion brazing joints of B 4 C ceramics using a Ni-Cr-Si-Fe-B interlayer. Various factors including shear strength, hardness, microstructure, interfacial phenomena, elemental diffusion patterns, formed compounds and phases, and fracture surfaces of the samples were analyzed and compared. The brazed sample at 1110 °C for 1/2 h exhibited the highest shear strength of 62 MPa. Increase of the bonding temperature to the optimum level (1090–1110 °C) enhances the fluidity of the molten interlayer, facilitating its diffusion into the porosities of the ceramic components. This increase also promotes higher interactions within the system, creating favorable conditions for element diffusion. However, surpassing the optimum temperature (1110–1130 °C) may lead to increased destructive reactions and intensify the impact of the coefficient of thermal expansion (CTE) mismatch, resulting in residual stresses and a subsequent decrease in bond strength. The excessive increase in the bonding temperature (1130–1150 °C) can lead to the excessive fluidity of the molten interlayer, potentially causing effusion onto the joint's fixture and damaging the samples. The results indicate the formation of various compounds between the elements of the interlayer and carbon and boron elements, including SiC, Ni 4 B 3 , CrB 2 , Fe 2 B, Ni 6 Si 2 B, and B 2 Fe 3 Ni 3 , at the fracture surface of the sample bonded at 1110 °C. The more substantial peaks of these compounds, compared to other samples, could be a reason for the higher strength of this particular sample. [ABSTRACT FROM AUTHOR]

To minimize bowing in a gallium nitride (GaN) template, which is caused by differences in the properties of the GaN film and the sapphire substrate, we studied how to offset bowing by directly growing GaN using the hydride vapor phase epitaxy (HVPE) method on the frontside of a pre-strained sapphire substrate prepared using a backside grinding process. The relationships between the respective thicknesses and stresses of the undamaged sapphire, damaged sapphire, and GaN layers were analyzed by deriving the bow formula, which is a modification of Freund's equation, and the theoretical formula-derived results were compared with experimentally determined values. The bow of the GaN template was measured using a micrometer, and the residual stresses in the GaN and sapphire, carrier mobilities, and GaN crystal qualities were measured using a micro-Raman spectrophotometer. The results confirmed the annealing effect on the damaged sapphire layer, and the introduction of pre-strained GaN templates facilitated easier bow control compared to that afforded by a conventional GaN template. Additionally, we identified trends and optimal conditions for changes in residual stress, carrier mobility, and crystal quality in GaN and the damaged sapphire layer based on layer thickness and stress variations. We explain the mechanisms responsible for changes in bow, stress, carrier mobility, and crystal quality of the GaN template. [Display omitted] • A pre-strained sapphire was introduced to minimize the bow in the GaN template. • The bow of the pre-strained GaN template was counterbalanced by epitaxial GaN growth. • Relationships between composed layers were interpreted using the induced bow formula. • Residual stress, carrier mobility, and crystallinity trends in GaN were analyzed. • Mechanisms governing bow and optical properties were elucidated. [ABSTRACT FROM AUTHOR]

In this study, the size of molten pool and the porosity of parts under different processing parameters are studied using numerical simulation. According to the results, the appropriate processing parameters were selected to simulate the temperature and residual stress distribution during the forming process of body-centered cube (BCC), face-centered cube (FCC) and rhombic dodecahedron (Dode) lattice structures. In addition, three lattice structures were fabricated via selective laser melting (SLM) technology, and quasi-static compression experiments were carried out to study their mechanical properties. The results show that the high temperature parts of the three structures are all under the node and their adjacent pillars, and the closer to the nodes, the higher the temperature. The residual stress of the Dode structure is the highest, reaching 1218.2 MPa. It is also found that the residual stress in the Z direction is the largest, which plays a dominant role in the forming process. Through compression experiments, it is found that diagonal shear failure occurs in all three lattice structures, and Dode shows the best compression performance. [ABSTRACT FROM AUTHOR]

In this paper, the butt joint of unequal thickness 410 ferritic stainless steel and RCL540 low-carbon alloy steel sheets are realized by laser welding. The effects of different laser powers on weld formability, mechanical properties, and residual stress in the welding process are investigated. It is observed that with increasing laser power, the heat accumulates at the bottom of the molten pool and weld metal, causing the ratios of upper and lower melt widths to decrease. The tensile test results show that all specimens fractured in the weak zone of the base metal on the stainless steel side at 10 mm from the weld seam. The residual stress distributions of the specimens are calculated using ABAQUS 2022 software and compared with the measurements of the blind-hole method. It is found that the stainless steel side produces tensile stresses, with the power increase offset by compressive stresses in the base metal. When the laser power is 1200 W, the welded joint has the best weld formability and mechanical properties and the least residual stress. The upper and lower melt width ratio is 1.17, the maximum microhardness of the weld metal is 374.7 HV, the maximum test force and tensile strength are 5617.5 N and 468.12 MPa, respectively, and the minimum values of the transverse and longitudinal stresses are −45.8 MPa and −106.4 MPa, respectively. [ABSTRACT FROM AUTHOR]

As stacking technologies, such as 2.5D and 3D packages, continue to accelerate in advanced semiconductor components, the singulation and thinning of Si wafers are becoming increasingly critical. Despite their importance in producing thinner and more reliable Si chips, achieving high reliability remains a challenge, and comprehensive research on the effects of these processing techniques on Si chip integrity is lacking. In this study, the impacts of wafer thinning and singulation on the fracture strength of Si wafers were systematically compared. Three different grinding processes, namely fine grinding, poly-grinding, and polishing, were used for thinning, and the resulting surface morphology and roughness were analyzed using scanning electron microscopy and an interferometer. In addition, the residual mechanical stress on the wafer surface was measured using Raman spectroscopy. The fracture strength of Si wafers and chips was assessed through three-point bending tests. Singulation, including blade dicing, laser dicing, and stealth dicing, was evaluated for its impact on fracture strength. Among these processes, polishing for wafer thinning exhibited the lowest full-width half maximum and intensity ratio of Raman shifts (I480/I520), indicating minimal residual stress and surface defects. Consequently, Si wafers and chips processed through polishing demonstrated the highest fracture strength. Moreover, the 60 µm thick Si wafers and chips showed the highest fracture strength compared with those with thicknesses of 90 and 120 µm, possibly because of the increased flexibility, which mitigates stress. Among the singulation methods, stealth dicing yielded the highest fracture strength, outperforming blade and laser dicing. The combination of wafer thinning via polishing and singulation via stealth dicing presents an optimal solution for producing highly reliable Si chips for 2.5D and 3D packaging. These findings may be valuable in selecting optimal processing technologies for high-reliability Si chip production in industrial settings. [ABSTRACT FROM AUTHOR]

Crack-free Stellite-6 alloy was fabricated using the laser powder bed fusion technique equipped with a heating module as the first attempt. Single tracks were printed with a build plate heated to 400 °C to identify the processing window. Based on the melt pool dimensions, two combinations (sample A: 300 W/750 mm/s and sample B: 275 W/1000 mm/s) were identified to print the cubes. The as-printed microstructure comprised FCC-Co dendrites with M7C3 in the interdendritic region. W-rich M6C particles were found in the overlapping regions between the melt pools, matching the Scheil simulations. However, gas pores were observed due to the higher nitrogen and oxygen content of the feedstock requiring hot isostatic pressing (HIP) at 1250 °C and 150 MPa for 2 h. Sample A was partially recrystallized with slightly coarsened M7C3, while sample B underwent complete recrystallization followed by grain growth along with higher coarsening of the M7C3 after HIP. The varying recrystallization behavior can be attributed to the difference in residual stresses and grain aspect ratio in the as-built condition dictated by laser power and scanning speed. The microhardness after HIP was slightly higher than its wrought counterpart, indicating no severe impact of post-processing on the properties of Stellite-6 alloy. [ABSTRACT FROM AUTHOR]

Broaching is a key manufacturing process that directly influences the surface integrity of critical components, impacting their functional performance in sectors such as aeronautics, automotive, and energy. Such components are subjected to severe conditions, including high thermomechanical loads, fatigue, and corrosion. For this reason, the development of predictive models is essential for determining the optimal tool design and machining conditions to ensure proper in-service performance. This study, therefore, presents a broaching digital twin based on hybrid modelling, which combines analytical, numerical, and empirical approaches to provide rapid and accurate predictions of the forces per tooth, local overloads, and surface topography irregularities. The digital twin was validated with a critical industrial case study involving fir-tree broaching of turbine discs made of forged and age-hardened Inconel 718. The accuracy of the digital twin was demonstrated by the results: the average error in force predictions was below 10%, and the model effectively identified the most critical teeth and zones prone to failure. It also predicted surface topography irregularities with an error of less than 15%. Interestingly, the relationship between surface topography irregularities and surface residual stress variations across the machined surface was observed experimentally for the first time. [ABSTRACT FROM AUTHOR]

Control of residual stresses (RS), inherent to fusion-based additive manufacturing (AM), process is important for the satisfactory mechanical performance of components. Recent work has attempted to control the RS profiles in AM components by applying mechanical peening between built layers. During laser powder bed fusion (LPBF), it has been shown that subsequent layer building does not relieve all the peening-induced compressive stresses. In this work, a similar study has been performed on a directed energy deposition (DED) process. It is shown that owing to the vastly different thermal profile in DED compared to LPBF, the compressive RS induced by peening, is completely alleviated during subsequent layer deposition for 316L stainless steel. Irrespective of the magnitude and depth, the peening-induced compressive stresses were not present in the final part. Experimental and numerical analyses revealed that stress relief due to intrinsic heating was insufficient to explain stress relaxation. Rather, the localized heating and constrained expansion from surrounding cold material was the mechanism responsible for strain redistribution and hence stress relaxation. [ABSTRACT FROM AUTHOR]

To understand and further improve the corrosion resistance of a medium electroless phosphorus nickel coating (9 wt% P) under high-temperature and corrosive conditions, the microstructural evolution of the coating after various treatments, including thermal and mechanical methods (such as Hammer Peening), was extensively studied. Complementary analytical techniques, including SEM, EDS, in situ and ex situ XRD, and micro-indentation, were employed for detailed analysis. The transformation of the deposit from its amorphous state to a distinct structure comprising Ni, Ni3P, and NiO due to thermal treatment (ranging from 20 to 800 °C) was examined. The evolution of microstructure with temperature and annealing duration was discussed, correlating with alterations in mechanical properties, particularly micro-hardness. At temperatures exceeding 310 °C, a phase transition occurred, characterized by co-precipitation of Ni and Ni3P, leading to a significant change in the coating's mechanical behavior. With further temperature elevation, nickel diffused toward the surface, initiating NiO formation at 500 °C. The coating's oxidation behavior during isothermal treatment at varied temperatures (up to 800 °C) was also explored. This investigation was supported by thermodynamic calculations. Additionally, simplified kinetic simulations with the Dictra module from Thermo-Calc were proven to be able to reproduce the oxidation behavior. Hammer peening treatment enhanced the coating's hardness in its as-deposited state by introducing residual stresses that affected the precipitation kinetics during subsequent heat treatment. However, this hardening effect was no longer evident after the thermal treatment. [ABSTRACT FROM AUTHOR]

The formation and distribution of residual stress during the micro-milling process significantly affect the crack resistance and service life of alumina bioceramics. This study aims to optimize the surface residual stress distribution by adjusting machining parameters, thereby improving the machining quality of alumina ceramics. A three-dimensional finite element model of alumina bioceramics was developed, and numerical simulations were conducted to analyze the effects of feed per tooth, cutting depth, and spindle speed on temperature and residual stress. The study further explores the patterns of residual stress variation. The results show that both surface temperature and residual tensile stress exhibit systematic trends with parameter changes. Specifically, surface residual tensile stress increases with cutting depth initially but decreases sharply once the cutting depth exceeds 25 μm. Residual tensile stress increases with spindle speed, reaching its peak at 21,000 r/min before stabilizing. Additionally, the residual tensile stress rises with feed per tooth at first but gradually declines when the value exceeds 25 μm/z. This research reveals the mechanisms by which micro-milling parameters influence surface temperature and residual stress in alumina bioceramics, providing theoretical guidance for optimizing micro-milling processes. The findings can also be extended to the micro-milling of other hard-to-machine materials, offering broad engineering application potential. [ABSTRACT FROM AUTHOR]

Surface integrity—comprising abrasive embedding, work hardening, and residual stress—is crucial for the performance of nickel-based superalloy components milled by abrasive waterjet (AWJ). Effective evaluation of this integrity is therefore essential. First, the effects of pure waterjet and small-size AWJ on the milled surface were analyzed, with abrasive embedding as a key indicator. It was found that small-size AWJ significantly reduced both the number and depth of abrasive particles embedded. Next, single-factor experiments determined the influence of AWJ process parameters on abrasive embedding, leading to the identification of optimal modification schemes (modification scheme 1 and modification scheme 2) for minimizing the number and depth of abrasives. Recommended processing parameters are waterjet pressure = 100 MPa, and step-over distance = 0.38 mm. Finally, it was observed that both modification schemes decreased surface hardness while significantly increasing residual compressive stress compared to the unmodified surface. These findings offer a theoretical and practical foundation for achieving high surface integrity in the milling of nickel-based superalloys using AWJ. [ABSTRACT FROM AUTHOR]

Electrochemical drilling (ECD) offers excellent potential for processing deep holes because it does not wear tools, does not create a remelting layer on the machined surface, and does not produce residual stress during machining. However, a normal single-hole tube electrode easily forms a spike at the bottom of the drilling hole, thereby destroying the flatness at the bottom. This phenomenon is clearly visible when drilling blind holes with large diameters. In this study, a tube electrode with multiple outlet holes is proposed to eliminate the spike and improve the flatness at the bottom of the hole. Specifically, a single outlet hole was discretized into multiple small-diameter outlet holes. The effects of the arrangement of the outlet holes on the electric field distribution over the workpiece surface and the flow field distribution in the machining gap were numerically investigated. The results generated according to the electric field showed that the outlet holes should be as small as possible and appropriately overlap to flatten the surface. The results generated according to the flow field indicated that increasing the number of outlet holes and their overlap ratio increased the electrolyte flow rate, but it also caused the flow fields to interfere with each other, resulting in an uneven distribution. Different tools were experimentally verified using stainless steel 20Cr13, and the stability of the process and machining quality were analyzed. The results showed that, for the given test parameters, higher machining quality and processing stability were obtained using a tool with 16 non-overlapping outlet holes. Furthermore, the discrete tube electrode was optimized using chamfered outlet holes. For a voltage of 25 V, feed speed of 0.8 mm/min, and electrolyte pressure of 0.2 MPa, a deep blind hole with a diameter of 22.43 ± 0.04 mm and depth of 71.28 mm was machined using the optimal tool, which had a roundness of 0.0201 mm, flatness of 52.46 µm, and taper of 0.1296°. [ABSTRACT FROM AUTHOR]