Search Results (120)

Metal/composite interfacial interactions are critical to the mechanical performance of Fiber Metal Laminates (FMLs). In this study, the feasibility of successively combining Vacuum-Assisted Resin Transfer Molding (VARTM) and Vacuum Bagging (VB) was investigated, a strategy that has not been reported in the literature for the fabrication of FMLs with 2/1 stacking configuration, using low-cost 3003-H14 aluminum alloy. The substrate was surface modified through mechanical abrasion and chemical etching in an ultrasonic bath with a 0.1 M NaOH solution, varying the exposure time (20, 40, and 60 min). These surfaces were characterized by optical microscopy and atomic force microscopy (AFM), conducting both qualitative and quantitative analyses of the two- and three-dimensional surface features associated with pore morphology. Additionally, their effects on interlaminar strength and Mode I failure modes of the adhesive joint at the metal/composite interface were evaluated. Micrographs of the surface variants revealed a systematic evolution of the metallic microstructure. The T-peel tests demonstrated that the microstructural features influenced the interlaminar behavior. The 40 min treatment exhibited the highest initial peak force (26.4 N) and the highest average peel force (12.4 N), with a predominantly cohesive mixed-mode failure, representing the most favorable configuration for maximizing adhesion at the metal/composite interface. Full article

This work presents a comprehensive study on the fabrication, microstructural evolution, and mechanical performance of hybrid aluminum matrix composites based on Al6060 alloy reinforced with ~2 wt.% TiB₂ and ~1 wt.% multi-walled carbon nanotubes (MWCNTs). The composites were produced via ultrasonically assisted stir casting followed by radial-shear rolling (RSR). The combined processing route enabled a uniform distribution of reinforcing phases and significant grain refinement in the aluminum matrix. SEM, EDS, XRD, and EBSD analyses revealed that TiB₂ particles acted as nucleation centers and grain boundary pinning agents, while MWCNTs provided a network structure that suppressed agglomeration of ceramic particles and enhanced interfacial load transfer. As a result, hybrid composites demonstrated a submicron-grained structure with reduced anisotropy. Mechanical testing confirmed that yield strength (YS) and ultimate tensile strength (UTS) increased by 67% and 38%, respectively, in the cast state compared to unreinforced Al6060, while after RSR processing, YS exceeded 115 MPa and UTS reached 164 MPa, with elongation preserved at 14%. Microhardness increased from 50.2 HV0.2 (base alloy) to 82.2 HV0.2 (hybrid composite after RSR). The combination of ultrasonic melt treatment and RSR thus provided a synergistic effect, enabling simultaneous strengthening and ductility retention. These findings highlight the potential of hybrid Al6060/TiB₂–MWCNT composites for structural applications requiring a balance of strength, ductility, and wear resistance. Full article

This study investigates the microstructural evolution and damage mechanisms of the nickel-based single-crystal superalloy DD9-thermal barrier coating (TBC) system under 1050 °C high-temperature oxidation, while conducting a comparative analysis of oxidation behavior with the DD6-TBC system. Results show that both systems have similar oxidation mechanisms but face long-term oxidation drawbacks: as oxidation time increases, the thermally grown oxide (TGO) evolves into a mixed oxide layer and an Al₂O₃ layer, with initial rapid TGO growth consuming Al in the bond coat (BC) and subsequent Al depletion slowing growth, though long-term TGO accumulation raises cracking and spallation risks. DD9 and DD6 substrates significantly affect substrate-BC interfacial interdiffusion: the interdiffusion zone (IDZ) and secondary reaction zone (SRZ) grow continuously (SRZ growing faster), and linear topologically close-packed (TCP) phases precipitate in the SRZ, spreading throughout the substrate and impairing high-temperature mechanical properties. Specifically, DD9’s IDZ growth rate is faster than DD6’s in the first 800 h of oxidation but slows below DD6’s afterward, reflecting DD9’s superior long-term oxidation resistance due to better temperature resistance and high-temperature stability. This study clarifies key high-temperature service disadvantages of the two systems, providing experimental support for coated turbine blade life evaluation and a theoretical basis for optimizing third-generation single-crystal superalloy-TBC systems to enhance high-temperature service stability. Full article

The development of lightweight, high-damping building materials is critical for enhancing the seismic resilience of civil infrastructure. This study introduces a novel approach to synergistically improve the damping and mechanical properties of cementitious composites by incorporating one-dimensional carbon nanotubes (CNTs) or two-dimensional graphene nanoplatelets (GNPs). The novelty lies in (1) a direct comparison of 1D versus 2D carbon nanomaterials efficacy within a vibration-relevant frequency range (0.5–2 Hz); (2) the use of the Ca(OH)₂ orientation index, derived from X-ray diffraction (XRD), to link microstructural texturing with macroscopic dynamic performance; and (3) establishing clear mechanistic link between carbon nanomaterials dispersion, pore structure evolution, and the resultant balance between stiffness and damping. Dynamic mechanical analysis identified an optimal dosage of 0.1% by weight for both nanomaterials. Comprehensive microstructural characterization (SEM, MIP, XRD, TGA/DTG) revealed that the carbon nanomaterials act as nucleation sites, promoting cement hydration and refining the pore structure. This structural enhancement concurrently improved mechanical strength and energy dissipation capacity. The primary damping mechanism was identified as interfacial friction and slippage at the nanofiller–matrix interface. These findings provide fundamental insights for the rational design of high-performance cementitious composites and offer an evidence-based pathway for creating advanced seismic-resistant materials. Full article

In the present study, the diffusion couple of solid CoCrFeMnNi HEA and liquid pure Al was prepared. The microstructure evolution and relevant interdiffusion behavior of CoCrFeMnNi HEA/Al solid–liquid diffusion couple processed by different parameters were characterized and investigated. Results demonstrated that the interfacial compounds in the order of Al(Co, Cr, Fe, Mn, Ni), Al₁₃(Co, Cr, Fe, Mn, Ni)₄ and Al₄(Co, Cr, Fe, Mn, Ni) were determined in the interdiffusion area along the direction from CoCrFeMnNi HEA to Al, and the precipitated Al₄(Cr, Mn) and Al₉(Co, Fe, Ni) phases were formed in the center of Al couple. In addition, the diffusion mechanism and activation energy of growth for each diffusion layer were revealed and determined. More importantly, the growth mechanism of each diffusion layer was also investigated and uncovered in detail. Meanwhile, the activation energy of each intermetallic layer was obtained by the Arrhenius equation and the linear regression method. It is anticipated that this present study would provide a fundamental understanding and theoretical basis for the high-entropy alloy CoCrFeMnNi HEA, potentially applied as the cast mold material for cast aluminum alloy. Full article

This paper provides an in-depth analysis of the microstructural characteristics and the chemical content of Polybutylene Terephthalate (PBT) composites that have different contents of Glass Fiber (GF). Blending of VALOX 420 (30 wt% GF/PBT) with unreinforced VALOX 310 allowed the composites to be prepared, with control of the concentration and distribution of the GF. The GF reinforcement and PBT matrix were characterized by an advanced microstructural spectrum and spatial analysis to show the influence of fiber density, dispersion, and chemical composition on performance. Findings indicate that GF content has a profound effect on microstructural properties and damage processes, especially traction effects in various regions of the specimen. These results highlight the significance of accurate control of GF during fabrication to maximize durability and performance, which can be used to inform the design of superior PBT/GF composites in challenging engineering applications. The implications of these results are relevant to a number of high-performance sectors, especially in automotive, electrical, and consumer electronic industries, where PBT/GF composites are found in extensive use because of their outstanding mechanical strength, dimensional stability, and thermal resistance. The main novelty of the current research is both the microstructural and chemical assessment of PBT/GF composites in different fiber contents, and this aspect is rather insufficiently studied in the literature. Although the mechanical performance or macro-level aging effects have been previously assessed, the Literature usually did not combine elemental spectroscopy or spatial microstructural mapping to correlate the fiber distribution with the damage mechanisms. Further, despite the importance of GF reinforcement in achieving the right balance between mechanical, thermal, and electrical performance, not much has been conducted in detail to describe the correlation between the microstructure and the evolution of damage in short-fiber composites. Conversely, this paper will use the superior spatial elemental analysis to bring out the effects of GF content and dispersion on micro-mechanisms like interfacial traction, cracking of the matrix, and fiber fracture. We, to the best of our knowledge, are the first to systematically combine chemical spectrum analysis with spatial mapping of PBT/GF systems with varied fiber contents—this allows us to give actionable information on material design and optimized manufacturing procedures. Full article

This study presents a comprehensive grayscale texture analysis framework for investigating the microstructural evolution of cement-based materials during hydration. High-resolution X-ray computed tomography (X-CT) slice images were analyzed across five hydration ages (12 h, 1 d, 3 d, 7 d, and 31 d) using three complementary methods: grayscale histogram statistics, fractal dimension calculation via differential box-counting, and texture feature extraction based on the gray-level co-occurrence matrix (GLCM). The average value of the mean grayscale value of slice (Mean_{G_AVE}) shows a trend of increasing and then decreasing. Average fractal dimension values (D_{B_AVE}) decreased logarithmically from 2.48 (12 h) to 2.41 (31 d), quantifying progressive microstructural homogenization. The trend reflects pore refinement and gel network consolidation. GLCM texture parameters—including energy, entropy, contrast, and correlation—captured the directional statistical patterns and phase transitions during hydration. Energy increased with hydration time, reflecting greater spatial homogeneity and phase continuity, while entropy and contrast declined, signaling reduced structural complexity and interfacial sharpness. A quantitative evaluation of parameter performance based on intra-sample stability, inter-sample discrimination, and signal-to-noise ratio (SNR) revealed energy, entropy, and contrast as the most effective descriptors for tracking hydration-induced microstructural evolution. This work demonstrates a novel, integrative, and segmentation-free methodology for texture quantification, offering robust insights into the microstructural mechanisms of cement hydration. The findings provide a scalable basis for performance prediction, material optimization, and intelligent cementitious design. Full article

Direct copper-plated ceramic (DPC) substrates have emerged as a favored solution for power device packaging due to their unique technical advantages. AuSn, characterized by its high hermeticity and environmental adaptability, represents the optimal sealing technology for DPC substrates. Through the application of vacuum sintering techniques and adjustment of peak temperatures (325 °C, 340 °C, and 355 °C), the morphology and composition of interfacial compounds were systematically investigated, along with an analysis of their formation mechanisms. A gradient aging experiment was designed (125 °C/150 °C/175 °C × oxygen/argon dual atmosphere × 600 h) to elucidate the synergistic effects of environmental temperature and atmosphere on the growth of intermetallic compounds (IMCs). The results indicate that the primary reaction in the sealing weld seam involves Ni interacting with Au-Sn to form (Ni, Au)₃Sn₂ and Au₅Sn. However, upon completion of the sealing process, this reaction remains incomplete, leading to a coexistence state of (Ni, Au)₃Sn₂, Au₅Sn, and AuSn. Additionally, Ni diffuses into the weld seam center via dendritic fracture and locally forms secondary phases such as δ(Ni) and ζ’(Ni). These findings suggest that the weld seam interface exhibits a complex, irregular, and asymmetric microstructure comprising multiple coexisting compounds. It was determined that Tpeak = 325 °C to 340 °C represents the ideal welding temperature range, where the weld seam morphology, width, and Ni diffusion degree achieve optimal states, ensuring excellent device hermeticity. Aging studies further demonstrate that IMC growth remains within controllable limits. These findings address critical gaps in the understanding of the microstructural evolution and interface characteristics of asymmetric welded joints formed by multi-material systems. Full article

This study proposes a coupled constitutive model that captures the anisotropic failure characteristics and damage evolution of nickel-based single-crystal (SX) superalloys under various temperature conditions. The model accounts for both creep rate and material damage evolution, enabling accurate prediction of the typical three-stage creep curves, macroscopic fracture morphologies, and microstructural features under uniaxial tensile creep for specimens with different crystallographic orientations. Creep behavior of SX superalloys was simulated under multiple orientations and various temperature-stress conditions using the proposed model. The resulting creep curves aligned well with experimental observations, thereby validating the model’s feasibility and accuracy. Furthermore, a finite element model of cylindrical specimens was established, and simulations of the macroscopic fracture morphology were performed using a user-defined material subroutine. By integrating the rafting theory governed by interfacial energy density, the model successfully predicts the rafting morphology of the microstructure at the fracture surface for different crystallographic orientations. The proposed model maintains low programming complexity and computational cost while effectively predicting the creep life and deformation behavior of anisotropic materials. The model accurately captures the three-stage creep deformation behavior of SX specimens and provides reliable predictions of stress fields and microstructural changes at critical cross-sections. The model demonstrates high accuracy in life prediction, with all predicted results falling within a ±1.5× error band and an average error of 14.6%. Full article

Aluminum matrix composites provide an ideal solution for lightweight brake disks, but conventional casting processes are prone to crack initiation due to inhomogeneous reinforcement dispersion, gas porosity, and inadequate toughness. To break the conventional trade-off between high wear resistance and low toughness of brake disks, this study fabricated a bimetallic structure of SiC_p/Al–Fe–V–Si aluminum matrix composite and cast ZL101 alloy using friction stir lap welding (FSLW). Then, the microstructural evolution, mechanical properties, and tribological behavior of the FSLW joints were studied by XRD, SEM, TEM, tensile testing, and tribological tests. The results showed that the FSLW process homogenized the distribution of SiC particle reinforcements in the SiC_p/Al–Fe–V–Si composites. The Al₁₂(Fe,V)₃Si heat-resistant phase was not decomposed or coarsened, and the mechanical properties were maintained. The FSLW process refined the grains of the ZL101 aluminum alloy through recrystallization and fragmented eutectic silicon, improving elongation to 22%. A metallurgical bond formed at the joint interface. Tensile fracture occurred within the ZL101 matrix, demonstrating that the interfacial bond strength exceeded the alloy’s load-bearing capacity. In addition, the composites exhibited significantly enhanced wear resistance after FSLW, with their wear rate reduced by approximately 40% compared to the as-received materials, which was attributed to the homogenized SiC particle distribution and the activation of an oxidative wear mechanism. Full article

To investigate the effects of heavy-metal-sludge sintered aggregates on the workability, mechanical properties, and fracture toughness of ultra-high-strength concrete (UHSC), this study systematically evaluated the influence of different aggregate replacement ratios and particle gradations on the fluidity, flexural strength, compressive strength, and fracture energy of UHSC. Microstructural characterization techniques including SEM, XRD, TG, and FTIR were employed to analyze the hydration mechanism and interfacial transition zone evolution. The results demonstrated the following: Fluidity continuously improved with the increase in the sintered aggregate replacement ratio, with coarse aggregates exhibiting the most significant enhancement due to the “ball-bearing effect” and paste enrichment. The mechanical properties followed a trend of an initial increase followed by a decrease, peaking at 15–20% replacement ratio, at which flexural strength, compressive strength, and fracture energy were optimally enhanced; excessive replacement led to strength reduction owing to skeletal structure weakening, with coarse aggregates providing superior improvement. Microstructural analysis revealed that the sintered aggregates accelerated hydration reactions, promoting the formation of C-S-H gel and Ca(OH)₂, thereby densifying the ITZ. This study identified 15–20% of coarse sintered aggregates as the optimal replacement ratio, which synergistically improved the workability, mechanical properties, and fracture toughness of UHSC. Full article

By applying different heat treatment processes (furnace cooling, air cooling, and water cooling), the stress–strain behavior of the localized interfacial region in weathering steel–stainless steel clad plates was investigated using nanoindentation, along with an analysis of interfacial microstructure formation and strengthening mechanisms. The results show that samples in the as-rolled (R), furnace-cooled (FC), air-cooled (AC), and water-cooled (WC) conditions exhibit distinct interfacial morphologies and local mechanical properties. A well-defined interfacial layer forms between the base and cladding materials, where a high density of dislocations, grain boundaries, precipitates, and nanoscale oxides significantly enhances interfacial strength, resulting in a yield strength (R_p0.2) much higher than that of either adjacent metal. Across the transition from weathering steel to stainless steel, the interfacial region consists of ferrite—interfacial layer—“new austenite”—stainless steel austenite. Its formation is predominantly governed by element diffusion, which is strongly influenced by the applied heat treatment. Variations in diffusion behavior significantly affect the microstructural evolution of the dual-phase transition zone at the interface, thereby altering the local mechanical response. Full article

Under the global initiative for automotive lightweighting to address climate challenges, this study investigates the microstructure evolution of steel–aluminum composites processed by hot equal-channel angular pressing (H-ECAP). Using 6061-T6 aluminum cores clad with 20 # low carbon steel tubes processed through 1–4 C-path passes (Φ = 120°, ψ = 30°), we demonstrate significant microstructural improvements. The steel component showed progressive grain refinement from 2.2 μm (1 pass) to 1.3 μm (4 pass), with substructures decreasing from 72.19% to 35.46%, HAGB increasing from 31.2% to 34.6%, and hardness increasing from 222 HV to 271 HV. Concurrently, aluminum experienced grain refinement from 59.3 μm to 28.2 μm, with recrystallized structures surging from 0.97% to 71.81%, HAGB increasing from 9.96% to 63.76%, and hardness increasing from 51.4 HV to 83.6 HV. The interfacial layer thickness reduced by 74% (29.98 μm to 7.78 μm) with decreasing oxygen content, containing FeAl₃, Fe₂Al₅, and minimal matrix oxides. Yield strength gradually increased from 361 MPa (one pass) to 372.35 MPa (four passes), accompanied by a significant enhancement in compressive strength. These findings reveal that H-ECAP’s thermomechanical coupling effect effectively enhances interface bonding quality while suppressing detrimental intermetallic growth, providing a viable solution to overcome traditional manufacturing limitations in steel–aluminum composite applications for sustainable mobility. Full article

Recent studies primarily focus on how the fiber content and curing age influence the pore structure and strength of concrete. However, The interfacial bonding mechanism in basalt-fiber-reinforced concrete hydration remains unclear. The lack of a long-term performance-prediction model and insufficient research on multi-field coupling effects form key knowledge gaps, hindering the systematic optimal design and wider engineering applications of such materials. By integrating X-ray computed tomography (CT) with the watershed algorithm, this study proposes an innovative gray scale threshold method for pore quantification, enabling a quantitative analysis of pore structure evolution and its correlation with mechanical properties in basalt-fiber-reinforced concrete (BFRC) and normal concrete (NC). The results show the following: (1) Mechanical Enhancement: the incorporation of 0.2% basalt fiber by volume demonstrates significant enhancement in the mechanical performance index. At 28 days, BFRC exhibits compressive and splitting tensile strengths of 50.78 MPa and 4.07 MPa, surpassing NC by 19.88% and 43.3%, respectively. The early strength reduction in BFRC (13.13 MPa vs. 22.81 MPa for NC at 3 days) is attributed to fiber-induced interference through physical obstruction of cement particle hydration pathways, which diminishes as hydration progresses. (2) Porosity Reduction: BFRC demonstrates a 64.83% lower porosity (5.13%) than NC (11.66%) at 28 days, with microscopic analysis revealing a 77.5% proportion of harmless pores (<1.104 × 10⁷ μm³) in BFRC versus 67.6% in NC, driven by densified interfacial transition zones (ITZs). (3) Predictive Modeling: a two dimensional strength-porosity model and a three-dimensional age-dependent model are developed. The proposed multi-factor model demonstrates exceptional predictive capability (R² = 0.9994), establishing a quantitative relationship between pore micro structure and mechanical performance. The innovative pore extraction method and mathematical modeling approach offer valuable insights into the micro-structural evolution mechanism of fiber concrete. Full article

The regulatory mechanism of vinyl acetate-ethylene (VAE) in the interfacial properties of silicate cement–silica fume repair mortar was investigated by examining the effects of varying VAE contents (0 wt.% to 10.0 wt.%) on mortar fluidity, mechanical strength, and interfacial bonding strength. The interface microstructure was also examined to reveal its evolution. Results indicate that VAE enhances mortar fluidity through micro-filling and interfacial activity. At 10% VAE content, fluidity reached 265 mm, a 14.97% increase. However, VAE introduction reduced compressive and flexural strength due to pore induction at low dosages and polymer network interference at high dosages. By improving interfacial stress transfer and refining calcium sulfoaluminate (AFt) and C-S-H crystals in the interfacial transition zone, VAE increased the tensile bonding strength of the repaired mortar to 2.1 MPa at 28 days, a 133.3% increase, according to microscopic analysis. Based on performance analysis, 5.0 wt.% VAE is optimal, increasing interfacial bonding strength by 133.3% while limiting compressive strength loss to 9.4%, thus achieving interfacial collaborative optimization of the repaired mortar. Full article