Microstructural Analysis Research Articles

Design of high performance Cu-Ni-Si alloys via a multiobjective strategy based on machine learning

Herein, the ultimate tensile strength and electrical conductivity of precipitation-strengthened Cu-Ni-Si alloys were simultaneously improved by utilizing a machine learning-based multiobjective design strategy. The multiobjective design strategy consists of five main steps: creating the initial dataset, generating alloy features, screening key alloy features, modeling and inversely designing, and experimental iteration. Of particular note is the constraint placed on the initial composition-properties dataset, considering the rules governing the addition of Co. This constraint ensures that the dataset adheres to the required specifications. To evaluate the optimized degree of the inverse design composition, a joint expectation improvement function was employed. This function effectively integrates the ultimate tensile strength and electrical conductivity. Through a process of five mutually reinforcing iterations of machine learning and experimentation, the combined property of the designed alloy surpasses the Pareto frontier initially formed by the collected data. Microstructure analysis further confirmed the significant precipitation strengthening effects achieved in the optimized alloy.

Prevention of weld decay in TIG welded AISI 304 steel pipes

Weld decay due to chromium carbide precipitation at grain boundaries in the heat affected zone (HAZ) during TIG welding of austenitic stainless steels. This issue is particularly significant concerning the welding of AISI 304 steels, commonly used in the food industry. Although this problem can be overcome with different methods, there are some restrictions. A novel technique for welding AISI 304 steel pipes is introduced to reduce weld decay and improve the mechanical properties. The use of this technique, which includes faster cooling after welding, significantly minimizes the time of precipitation of chromium carbide. Temperature measurements and microstructural analyses monitor precipitation and the impact of the technique on the mechanical characteristics of AISI 304 steel pipes was assessed through hardness and hoop tensile tests. There was a 6% increase in hardness values observed in the HAZ region. Furthermore, a 16.7% increase in maximum load and a 127.4% increase in elongation. The reduction in chromium carbide precipitation observed in the microstructural analysis was confirmed through the double loop electropotentiokinetic reactivation (DLEPR) test, specifically for assessing intergranular corrosion. With the novel method, there was a 25% increase in corrosion resistance in the HAZ and a 40% increase in the weld zone.

Investigating the Electrocatalytic Oxygen Evolution Reaction of Hydrothermally Synthesized NiFe2O4 Nanoparticles

In this study, nickel ferrite (NiFe2O4) nanoparticles were synthesized using the hydrothermal method at various pH values. The objective was to investigate the influence of pH variation on particle size and electrocatalytic activity. The formation of cubic phase nanoparticles was confirmed through X-ray diffraction (XRD) analysis. To characterize the electrochemical properties, the nickel ferrite nanoparticles were coated onto a stainless steel substrate using the doctor blade technique. The microstructural analysis was conducted using scanning electron microscopy (SEM). The samples were further analyzed using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The average crystallite size, determined from the XRD pattern, was approximately 40 nm. SEM images revealed a conversion from nanoplates to a granular morphology. The synthesized electrode exhibited an overpotential of 392 mV at 10 mA/cm2 and demonstrated good stability for 5 hours. These findings highlight the excellent electrocatalytic activity of nickel ferrite nanoparticles for the oxygen evolution reaction (OER).

Accelerated pork salting using needle electrode-derived pulsed electric fields

This study aimed to evaluate the effects of pulsed electric field (PEF) pretreatment on the NaCl content, protein composition, and microstructure of pork during the marination process. The results showed that needle PEF could promote salt penetration into the center of pork pieces. Under optimal PEF conditions (3.0 kV/cm, 200 Hz, and 2400 pulses), the marination time could be reduced by almost 12 h. Protein characterization also revealed that PEF pretreatment changes myofibrillar protein properties by promoting salt penetration toward the center of pork. Furthermore, microstructural analysis demonstrated that the enhanced marination effect could be attributed to the PEF treatment-induced expansion of gaps between muscle bundles. Industrial relevanceIn this study, a PEF-assisted curing technique significantly (P < 0.05) improved salt penetration into the center of pork. Reducing the differences between internal and external salt concentrations can produce a more homogeneous marinade and reduce the marination time. Our findings suggest that PEF pretreatment is a promising and effective pretreatment technique for curing meat products.

Annealing response and yielding behavior of cold rolled advanced HSLA steels

High-strength low-alloy (HSLA) steel is well established in car body manufacturing. They comprise a lean low-carbon alloy concept and can be produced by a wide variety of processing routes. However, cold-rolled HSLA steels are typically limited to a yield strength of 460 MPa by current standards. This research work will present a concept of extending the yield strength range of cold-rolled HSLA steels to above 500 MPa. A key aspect is to find the right balance between recovery and recrystallization of the cold rolled matrix during the annealing stage thereby mitigating the influence of solute and precipitated niobium. Additional solute draging power was introduced by alloying molybdenum to one of the investigated steels. A detailed microstructural analysis using transmission electron microscopy revealed that under recovery annealing conditions an ultrafine-grained microstructure with ferrite grain sizes between 0.5 and 1 μm can be established leading to large strength contribution via the Hall-Petch relationship. Strength losses related to partial recrystallization can be recovered to an extent of around 200 MPa by the precipitation of nano-sized niobium carbide particles. It is demonstrated that the presence of niobium and molybdenum in solute condition have the most prominent influence on obstructing recrystallization via solute drag. It is furthermore shown that the magnitude of precipitation strengthening correlates with the Lüders strain. The analysis of the work hardening behavior indicated that the n-value in ultrafine-grained condition approaches a lower limit value of 0.03 and raises to above 0.2 with progressing recrystallization as well as precipitation strengthening. The detailed evaluation of the tensile characteristics indicates that the strength limit for these HSLA steels ranging between 830 and 880 MPa is reached when the average grain size is reduced to 0.46 μm. The results of this study used to define robust processing conditions to securely produce steel grades in the 600-800 MPa yield strength range.

Prediction on partial replacement of cement and coarse aggregate by zeolite powder and steel slag in high-performance concrete

High performance concrete is obtained by the inclusion of mineral admixtures like silica fume and fly ash in the concrete. The research explores the viability and performance of sustainable concrete by introducing zeolite powder as a partial substitute for cement and steel slag as a partial replacement for coarse aggregate in M-70 grade concrete. Zeolite powder, possessing pozzolanic properties, is a natural or synthetic aluminosilicate material, while steel slag is an industrial byproduct with potential as an alternative aggregate source. The main objective is to investigate the impact of zeolite powder and steel slag on the development of High-Performance Concrete (M-70) in accordance with Bureau of Indian standards. The formulation of high-performance concrete involved replacing 12.5%, 15%, and 17.5% of the cement with zeolite powder and varying the proportion of steel slag as a replacement for coarse aggregate (ranging from 30% to 55%). A comprehensive mechanical test was conducted on these specimens and compared with conventional concrete. Among the 19 mixes, the optimal combination was identified, incorporating 15% zeolite powder as a cement replacement and 45% steel slag as a coarse aggregate replacement, resulting in superior performance compared to conventional concrete. This mix was further studied for non-destructive testing, and microstructural analysis. Subsequently, the experimental results were compared with predicted outcomes using the Taguchi method. The close alignment between the values obtained experimentally and those predicted further validates the effectiveness of the optimized mix.

Heterogeneous Multi-Phase Grains Improving the Strength-Ductility Balance in Warm-Rolled Fe-18Mn-3Ti Steel

The thermal properties, microstructure, and mechanical properties of Fe-18Mn-3Ti (wt%) were investigated, focusing on the effects of different heat-treatment processes. Results revealed that the 450 °C warm-rolling sample (450 WR) exhibited promising mechanical properties. Specifically, this sample displayed a yield strength of 988 MPa, an ultimate tensile strength of 1052 MPa, and total elongation of 15.49%. Consequently, a favorable strength-ductility balance was achieved. The strain-hardening ability surpassed that of the cold rolling sample (CR). Microstructure analysis indicated the simultaneous occurrence of dynamic equilibrium between grain deformation and re-crystallization because of the co-influence of thermal and strain in the warm rolling process. This desirable mechanical property was attributed to the presence of a multi-phase (α-martensite, austenite, and ε-martensite) and heterogeneous microstructure. The improvement of ultimate tensile strength was based on grain refinement, grain co-deformation, and the transformation-induced plasticity (TRIP) effect in the early stage of plastic deformation (stage Ⅰ). The improvement of ultimate elongation (TEL) was ascribed to the TRIP effect in the middle stage of plastic deformation (stage Ⅱ).

Mechanical, Durability, and Microstructure Assessment of Wastepaper Fiber-Reinforced Concrete Containing Metakaolin

This study evaluates the potential use of discarded plasterboard paper as fibers from buildings to reinforce concrete. Various concentrations of wastepaper fibers (0.5%, 1%, 1.5%, 2%, and 2.5% by weight of the binder) were investigated in this research. To mitigate the water absorption effect of the paper fibers, metakaolin was employed as a partial cement replacement. The results demonstrate that the inclusion of the wastepaper fiber enhances the mechanical and durability performance of the concrete. The optimal fiber proportion was identified as 1%, leading to a 29% increase in the compressive strength, a 38% increase in the splitting tensile strength, a 12% decrease in the water absorption, and a 23% decrease in the drying shrinkage with respect to the concrete containing 20% metakaolin. However, exceeding this optimal fiber content results in decreased mechanical and durability properties due to the fiber agglomeration and non-uniform fiber distribution within the concrete matrix. Based on the microstructural analysis, the improved performance of the concrete is ascribed to decreased porosity, more refined pore structure, and reduced propagation of microcracks within the concrete matrix in the presence of wastepaper fiber. According to the results, concrete containing 20% metakaolin and 1% wastepaper fiber exhibits durability and mechanical properties comparable to those of the traditional concrete. This finding highlights the significant promise of reducing dependency on conventional cement and incorporating suitable recycled materials, such as discarded plasterboard, and secondary by-products like metakaolin. Such a strategy encourages the preservation of resources, reduction in carbon dioxide emissions, and a decrease in the ecological footprint resulting from concrete production.

Simulation and Characterization of Micro-Discharge Phenomena Induced by Glitch Micro-Defects on an Insulated Pull Rod Surface

The reliability of GIS (gas-insulated switchgear) circuit breakers significantly depends on the condition of the insulated pull rods, with micro-defects on their surface posing a potential risk for micro-discharges and breakdown incidents. Experimentally investigating these micro-discharges is challenging due to their minute nature. This study introduces a framework to examine the linkage between micro-defects and micro-discharges, coupled with numerical simulations of the micro-discharge process in insulated pull rods afflicted by surface infiltration flaws under operational conditions. Initially, samples containing micro-defects were sectioned via water jet cutting for microstructural analysis through white light interferometry. Subsequently, a two-dimensional axisymmetric model simulating positive corona discharge from a needle to a plate electrode was employed to derive the relationship between charged particle density and the electric field in SF6 and air. Building on these observations, a micro-discharge model specific to micro-defects was developed. Comparative analysis of micro-discharge behaviors in SF6 and air for identical defect types was conducted. This research framework elucidates the discharge dynamics of charged particles in SF6 and air during micro-discharge events, shedding light on the mechanisms underpinning micro-discharges triggered by insulation rod defects.

Influence of cement and water content on the multifaceted capabilities of a self-sensing cement-based geocomposite: a comprehensive analysis

This study investigates the synergistic effects of cement, water, and hybrid carbon nanotubes/graphene nanoplatelets (CNT/GNP) concentrations on the mechanical, microstructural, durability, and piezoresistive properties of self-sensing cementitious geocomposites. Varied concentrations of cement (8% to 18%), water (8% to 16%), and CNT/GNP (0.1% to 0.34%, 1:1) were incorporated into cementitious stabilized sand (CSS). Mechanical characterization involved compression and flexural tests, while microstructural analysis utilized dry density, apparent porosity, water absorption, and non-destructive ultrasonic testing, alongside TGA, SEM, EDS, and x-ray diffraction analyses. The durability of the composite was also assessed against 180 Freeze-thaw cycles. Moreover, the piezoresistive behavior of the nano-reinforced CSS was analyzed during cyclic flexural and compressive loading using the four-probe method. The optimal carbon nanomaterials (CNM) content was found to depend on the water and cement ratios. Generally, elevating the water content led to a rise in the CNM optimal concentration, primarily attributed to improved dispersion and adequate water for the cement hydration process. The maximum increments in flexural and compressive strengths, compared to plain CSS, were significant, reaching up to approximately 30% for flexural strength and 41% for compressive strength, for the specimen containing 18% cement, 12% water, and 0.17% CNM. This improvement was attributed to the nanoparticles’ pore-filling function, acceleration of hydration, regulation of free water, and facilitation of crack-bridging mechanisms in the geocomposite. Further decreases in cement and water content adversely impacted the piezoresistive performance of the composite. Notably, specimens containing 8% cement (across all water content variations) and 10% cement (with 8% and 12% water content) showed a lack of piezoresistive responses. In contrast, specimens containing 14% and 18% cement displayed substantial sensitivity, evidenced by elevated gauge factors, under loading conditions.

Strategy for developing aluminum alloy-based solid structure with homogeneous properties in the overlapping direction using wire arc additive manufacturing

This research investigates the strategy for developing large-scale solid aluminum structures with multi-bead multi-layer (MBML) overlapping using wire-arc additive manufacturing (WAAM). The study addresses challenges, i.e. material accumulation, surface irregularities, and inter-bead and inter-layer gaps, by examining deposits’ geometrical characteristics, process parameters, and deposition methods. Initial test coupon solid blocks are printed and analyzed using optical microscopy, and subsequent statistical optimization leads to the successful printing of a defect-free 140 mm × 150 mm × 28 mm solid block. The flat surface achieved in the MBML structure is attributed to maintaining an optimal overlap coefficient and a parabolic profile with the maximum width at the base. Microstructural analysis reveals the absence of fusion gaps, with an average porosity of 11.7 ± 2.45%, due to hydrogen evolution and reheating effects, with few larger pores near fusion lines. The microstructural and mechanical analyses confirm the homogeneity of properties along the overlapping direction (OD), with microhardness averaging 85.80 ± 6.63 HV0.1 and tensile strength of 161.55 ± 1.19 MPa with 2.18 ± 0.08% elongation. Microhardness fluctuations along the OD are attributed to fusion boundaries, partially melted and heat-affected zones. The research revealed that careful consideration of bead geometry and process parameters is crucial for achieving defect-free aluminum solid structures in WAAM through MBML overlapping.

Influence of a Preageing Treatment on the Cluster Formation and the Further Ageing Route in Al–Mg–Si Extrusion Alloys

Herein, the influence of one‐ and two‐step preageing treatments prior to the artificial ageing step to peak age condition for three different 6xxx alloys, from low to high alloy content, is investigated. Analysis of the preaged conditions using atom probe tomography (APT) reveals a broad distribution of Mg and Si clusters, with some instances of Guinier‐Preston I zones present. Additionally, the high alloyed system exhibits a growth of precipitates toward a needle‐like shaped. These clusters formed during the preageing treatment serve as nucleation sites in the subsequent artificial ageing treatment, leading to an increase in hardness. Microstructural analysis conducted using transmission electron microscopy and APT demonstrates a reduction in the average precipitate length and a more narrow size distribution for T6 condition. This indicates that the preageing treatment results in a decreased portion of already overaged precipitates compared to the direct aged condition. Consequently, the more narrow size distribution of the precipitates leads to more effective hardening of the material, as a higher portion of precipitates is at or close to their optimum size. The investigations highlight the significant influence and positive effect of a preageing treatment at lower temperatures on the subsequent artificial ageing treatment.

Bambusa balcooa bamboo-reinforced concrete beams: experimental and FEM investigation for energy-efficient pavement construction.

This study explores the viability of using Bambusa bambos, sourced from Madhya Pradesh, India, as a reinforcement material in continuously reinforced concrete pavement (CRCP) construction, aiming to assess its potential as a sustainable alternative to traditional steel reinforcement. The research encompasses a comprehensive evaluation of physical and mechanical properties, including tensile, compressive, and bending strengths, and a detailed microstructural analysis using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) of Bambusa bambos. The study involved finite element analyses that modeled bamboo-reinforced concrete (BRC) beams, exploring the impact of horizontal and vertical placements of bamboo strips on flexural behavior under bending loads. The analysis aided in observing compressive and tensile stresses generated in concrete and bamboo, with specific FEA results indicating that beams with vertically aligned bamboo strips in both the compression (compressive stress of 16.90MPa for beam B1) and tension zones (tensile stress of 7.22MPa for beam B1) withstand flexural stresses effectively. Additionally, the multi-criteria decision-making approach using the TOPSIS method to rank different beam designs. Key findings obtained from FEA indicate that the vertical alignment of bamboo strips in both the compression and tension zones of the beams is optimally effective in handling flexural stresses.

Design and additive manufacturing of bionic hybrid structure inspired by cuttlebone to achieve superior mechanical properties and shape memory function

Abstract Lightweight porous materials with high load-bearing, damage tolerance and energy absorption as well as intelligence of shape recovery after material deformation are beneficial and critical for many applications, e.g., aerospace, automobiles, electronics, etc. Cuttlebone produced in the cuttlefish has evolved vertical walls with the optimal corrugation gradient, enabling stress homogenization, significant load bearing, and damage tolerance to protect the organism from high external pressures in the deep sea. This work illustrated that the complex hybrid wave shape in cuttlebone walls, becoming more tortuous from bottom to top, creates a lightweight, load-bearing structure with progressive failure. By mimicking the cuttlebone, a novel bionic hybrid structure (BHS) was proposed, and as a comparison, a regular corrugated structure (RCS) and a straight wall structure (SWS) were designed. Three types of designed structures have been successfully manufactured by laser powder bed fusion with NiTi powder. The LPBF-processed BHS exhibited a total porosity of 0.042% and a good dimensional accuracy with a peak deviation of 17.4 μm. Microstructural analysis indicated that the LPBF-processed BHS had a strong (001) crystallographic orientation and an average size of 9.85 μm. Mechanical analysis revealed the LPBF-processed BHS could withstand over 25 000 times its weight without significant deformation and had the highest specific energy absorption value (5.32 J/g) due to the absence of stress concentration and progressive wall failure during compression. Cyclic compression testing showed that LPBF-processed BHS possessed superior viscoelastic and elasticity energy dissipation capacity. Importantly, the uniform reversible phase transition from martensite to austenite in the walls enables the structure to largely recover its pre-deformation shape when heated (over 99% recovery rate). These design strategies can serve as valuable references for the development of intelligent components that possess high mechanical efficiency and shape memory capabilities.

Assessing the impact of sargassum algae biodiesel blends on energy conversion in a modified single-cylinder diesel engine with a silica-incorporated diamond-like coated piston

ABSTRACT As coal and oil reserves deplete, the world is shifting to alternative fuels and renewable energy. Researchers are exploring a cleaner alternative to fossil fuels for powering automobiles. In this investigation, biodiesel was synthesized from brown marine algae (Sargassum algae) using transesterification process. Silica-incorporated diamond-like coating (DLC) was done on the engine piston by using the chemical vapor deposition (CVD) process with flow rate of 7sccm of C2H2. Three different coating thicknesses, such as 50,100, and 150 µm, were employed on the CI engine piston. Mechanical properties such as hardness, wear, and microstructure analysis were investigated. Analysis of mechanical characteristics reveals that pistons with a 100 μm coating have enhanced characteristics compared to those with other pistons. Using a 100 μm silicon coated piston on a single-cylinder Kirloskar engine, four blends (B10, B20, B30, and B40) were compared to neat diesel. At maximum engine load conditions, the B40 blends produced 42 ppm of HC whereas neat diesel with 19 ppm which is 57% higher than diesel and CO emission concentration increased by 4.9% than diesel. Similarly, brake-specific fuel consumption was observed at maximum load conditions for diesel with 0.18 kg/kWh and 0.20 kg/kWh for B10D90 which is 9.54% higher than diesel. As a result, it is critical to recognize the importance of sargassum’s potential for producing sustainable energy toward green globalization.

Microstructure, Hardness, Wear Resistance, and Corrosion Resistance of As-Cast and Laser-Deposited FeCoNiCrAl0.8Cu0.5Si0.5 High Entropy Alloy

FeCoNiCrAl0.8Cu0.5Si0.5 high-entropy alloys were fabricated using vacuum induction melting and laser deposition processes, followed by a comparison of the structural and mechanical properties of two distinct sample types. The as-cast FeCoNiCrAl0.8Cu0.5Si0.5 alloy is comprised of BCC1, BCC2, and Cr3Si phases, while the laser-deposited alloy primarily features BCC1 and BCC2 phases. Microstructural analysis revealed that the as-cast alloy exhibits a dendritic morphology with secondary dendritic arms and densely packed grains, and the laser-deposited alloy displays a dendritic structure without the formation of granular interdendritic regions. For mechanical properties, the as-cast FeCoNiCrAl0.8Cu0.5Si0.5 alloy demonstrated higher hardness than the as-deposited alloy, with values of 586 HV0.2 and 557 HV0.2, respectively. The wear rate for the as-cast alloy was observed at 3.5 × 10−7 mm3/Nm, with abrasive wear being the primary wear mechanism. Conversely, the as-deposited alloy had a wear rate of 9.0 × 10−7 mm3/Nm, characterized by adhesive wear. The cast alloy exhibited an icorr of 4.062 μA·cm−2, with pitting as the form of corrosion. The laser-deposited alloy showed an icorr of 3.621 μA·cm−2, with both pitting and intergranular corrosion observed. The laser-deposited alloy demonstrated improved corrosion resistance. The investigation of their microstructure and mechanical properties demonstrates the application potential of FeCoNiCrAl0.8Cu0.5Si0.5 alloys in scenarios requiring high hardness and enhanced wear resistance.

Research on Low-Cost High-Viscosity Asphalt and Its Performance for Porous Asphalt Pavement

To develop a cost-effective, high-viscosity asphalt for porous asphalt pavement, we utilized SBS, tackifier, and solubilizer as the main raw materials, identified the optimal composition through an orthogonal experiment of three factors and three levels, and prepared a low-cost high-viscosity asphalt. We compared its conventional and rheological properties against those of rubber asphalt, SBS modified asphalt, and matrix asphalt, employing fluorescence microscopy and Fourier transform infrared spectroscopy for microstructural analysis. The results indicate that the optimal formula composition for high-viscosity asphalt was 4–5% styrene-butadiene-styrene (SBS) + 1–2% tackifier +0–3% solubilizer +0.15% stabilizer. The components evenly dispersed and the performances were enhanced with chemical and physical modification. Compared with SBS modified asphalt, rubber asphalt, and matrix asphalt, the softening point, 5 °C ductility, and 60 °C dynamic viscosity of high-viscosity asphalt were significantly improved, while the 175 °C Brookfield viscosity was equivalent to SBS modified asphalt. In particular, the 60 °C dynamic viscosity reaches 383,180 Pa·s. Rheological tests indicate that the high- and low-temperature grade of high-viscosity asphalt reaches 88–18 °C, and that high-viscosity asphalt has the best high-temperature resistance to permanent deformation and low-temperature resistance to cracking. It can save about 30% cost compared to commercially available high-viscosity asphalt, which is conducive to the promotion and application of porous asphalt pavement.

Innovating with potassium-modified ceramic powder geopolymer mortar and the integration of recycled aggregates

This study develops an environmentally friendly geopolymer mortar (GM) that incorporates ceramic powder (CP) and recycled aggregate (RA), optimized through the use of potassium hydroxide (KH) and potassium silicate (KS) as alkaline activators under varied molarities and curing conditions. The research methodically evaluates the replacement of ground granulated blast furnace slag (GBFS) with CP at different ratios (25 %, 50 %, 75 %, and 100 %). Subsequently, RA is replaced with marble powder (MP) and glass powder (GP) in proportions of 25 %, 50 %, and 75 %. Physical and mechanical properties, including unit weight, water absorption, ultrasonic pulse velocity (UPV), compressive strength and flexural strength, are evaluated at various curing times. Furthermore, exposure to elevated temperatures and freezing-thawing cycles test the material's durability. Specifically, a peak improvement of 45.4 % in compressive strength is observed with 50 % GP replacement of 100 % RA, while high temperature resistance tests show increases of 28.57 % in compressive strength and 26.75 % in flexural strength at 800 °C. The incorporation of GP also has a minimal impact on freezing-thawing resistance, with a slight reduction of 5.84 % in compressive strength and 5.78 % in flexural strength. Advanced microstructural analysis using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared (FT-IR) spectroscopy reveals intricate details, confirming the significant efficacy of GP in improving GM properties. Furthermore, the analysis establishes a 94 % correlation between UPV and compressive strength and demonstrates the effectiveness of the material composition and processing conditions tailored to this study.

Effect of heat treatment processes on the Cu-electrodeposited through glass vias (TGV) plate

Based on laser-induced deep etching technology and through-hole filling techniques, TGV interposers were successfully fabricated. The residual stress in the Cu overburden film directly affects the yield improvement after subsequent grinding of the interposer. Therefore, we studied the evolution of residual stress, microstructural changes, and micro-nano mechanical properties within the Cu overburden film after heat treatment at different temperatures. Residual stress analysis using the sin2Ψ method with an X-ray diffractometer (XRD) indicates that during the process of increasing temperature from 100°C to 200°C, the internal residual stress in the Cu overburden film changes from compressive stress to tensile stress. Furthermore, the maximum absolute value of the residual stress, 70.09 MPa, appears at room temperature, and the minimum absolute value of the residual stress, 15.59 MPa, occurs after the heat treatment process at 200°C. Electron backscatter diffraction (EBSD) microstructural analysis shows that the application of heat treatment can effectively accelerate static recrystallization (SRX), promote a higher proportion of high-angle grain boundaries (HAGB), and refine grain size. Additionally, a (001) preferred orientation at high residual stress states and a (111) preferred orientation at low residual stress states are observed. Nanoindentation test results indicate that the Cu overburden film treated at 100°C has the most potential for removal during the grinding process.

Microstructural evolution and property evaluation of in‐situ Al‐MgAl2O4 nanocomposite prepared by ɣ‐Al2O3 and ultrasonication‐assisted impeller mixing

Synthesis of nanocomposites is challenging due to the difficulties in achieving homogeneous distribution of reinforcing particles in metal. In this paper, an in‐situ Al‐MgAl2O4 nanocomposite billet was prepared by the reaction of ɣ‐Al2O3 with molten Al and ultrasonication‐assisted impeller mixing. The microstructure of the composite showed homogeneously distributed MgAl2O4 crystals alongside their clusters in the Al matrix. Microstructural analysis revealed MgAl2O4 crystals distributed from 20 nm to 4 μm in size. The hardness was found to vary within the composite from 50 Hv for the matrix to 140 Hv for particle cluster regions. The grain size was reduced from 1000 μm in reference metal (CP Al) to 100 μm in the composite. The compression strength of the composite was increased substantially and higher strain hardening effect in comparison with Al was noticed in the compression test. The signatures of extensive plastic deformation such as dislocation pileups, deformed grains, grain boundary pinning etc. were observed in the composite via transmission electron microscopy. Damping properties of as‐cast composite were higher than those of CP Al in the temperature range from room temperature to 350 °C. After rolling the composite up to 40% reduction, the damping capacity (Tanδ) of the composite was found to increase marginally after 150 °C. Higher damping was found to reoccur after the annealing treatment of the composite. The improvement in damping capacity at RT was possibly influenced by the micron sized MgAl2O4 and at higher temperatures by the nano‐sized MgAl2O4 crystals. The reoccurrence of higher damping in the annealed composite underlined the stability of finer grains due to the grain boundary pinning by nano‐sized MgAl2O4 crystals. The studies on the damping property of the composite displayed the benefits of having dual size distribution of MgAl2O4 crystals (nm and μm) in the composite.This article is protected by copyright. All rights reserved.