Grain boundaries precipitates (GBPs) represent a critical factor responsible for plasticity degradation in aged high-strength Al-Mg-Mn alloys. However, the crystal structure, chemical composition, and underlying role of Mn-rich precipitates in the crack nucleation of a Selective Laser Melting (SLM) fabricated Al-Mg-Mn-Sc-Zr alloy remain poorly understood. Herein, we confirm that the Mn-rich precipitates are L1₂-structured Al3(Mn, Si), whose intrinsic physical properties are further studied by first-principles calculations. Meanwhile, the interactions between L1₂-Al3(Mn, Si) and dislocations are systematically investigated using molecular dynamics simulations to elucidate the stress evolution of microstructure during in-situ tensile deformation. Acting as obstacles to dislocation motion, such precipitates become vulnerable sites during both crack initiation and propagation. The findings offer useful insights for clarifying the specific role of precipitates in additively manufactured Al alloys designed for simultaneous high strength and exceptional damage tolerance.
Aluminum matrix composites reinforced with ceramic nanoparticles have attracted considerable attention for lightweight structural and marine applications because of their potential to simultaneously improve mechanical performance and corrosion resistance. In this study, AA5083 aluminum matrix composites reinforced with 0.0–6.0wt. % nano-sized SiC particles were fabricated by stir casting to investigate the relationships among microstructural evolution, mechanical properties, and corrosion behavior.Microstructural characterization revealed that low to moderate SiC additions (1.5–3.0wt. %) promoted grain refinement, relatively uniform particle dispersion, and effective matrix–particle interaction, whereas higher reinforcement contents resulted in particle agglomeration and increased microstructural heterogeneity. The average grain size decreased from 83 μm in unreinforced AA5083 to 65 μm in the reinforced composites. Consequently, the ultimate tensile strength increased from 261MPa to 286MPa, while the hardness increased from 70 HV to 97 HV. The 3.0wt. % SiC composite exhibited the highest toughness (~81 MJ/m³), indicating the optimum balance between strength and ductility. XRD and SEM–EDS analyses confirmed the incorporation of nano-SiC particles and their role in microstructural evolution.At higher reinforcement contents, particle agglomeration promoted localized stress concentrations and increased susceptibility to localized corrosion. The corrosion rate increased from approximately 0.017mm·yr⁻¹ for unreinforced AA5083 to 0.037mm·yr⁻¹ for the 6.0wt. % SiC composite. The results demonstrate that particle dispersion, grain refinement, and matrix integrity govern the mechanical and corrosion performance of AA5083/nano-SiC composites, with 3.0wt. % SiC providing the optimum overall performance.
ZnO-based nanorods were synthesized on glass substrates via dip-coating and hydrothermal methods, and the influence of hexamethylenetetramine (HMTA) concentration on structural, optical, and photodetector performance was systematically investigated. The HMTA concentration was varied by adjusting the ZnO:HMTA molar ratio as 1:0 (without HMTA), 1:0.3, 1:0.5, 1:1.0, 1:1.5, 1:3.0, and 1:4.0. XRD analyses confirmed the formation of single-phase hexagonal wurtzite ZnO with variations in (002) preferential orientation and crystallinity depending on HMTA concentration, indicating the influence of HMTA on crystal growth behavior. SEM results demonstrated that HMTA strongly controls nanorod morphology, yielding optimized one-dimensional structures with high aspect ratio. Optical measurements revealed a direct band gap ranging from 3.24 to 3.27eV. Photodetector characterization demonstrated that the device performance strongly depends on HMTA concentration in the visible-light region. The optimized sample (ZH15) exhibited the highest responsivity (9.90 × 10-3A/W) and specific detectivity (2.97 × 109 Jones), together with the fastest response/recovery time of 6.4/7.2s at 20mW/cm2 under 5V bias. Device performance exhibited a concentration-dependent trend, increasing with HMTA content up to an optimal ZnO:HMTA molar ratio, followed by a decline at higher concentrations. This result indicates that an appropriate balance in HMTA is essential, and precise optimization is crucial for achieving high-performance ZnO photodetectors. These findings demonstrate that HMTA optimization is an effective strategy for controlling ZnO nanorod properties and improving visible-light photodetector performance without additional sensitizing materials or complex architectures.
In this work, a series of Sm-doped Bi3YO6 electrolytes is synthesized via a simple solid-state reaction route. The optimal composition, Bi3Y0.80Sm0.20O6 (BYSO), exhibits a bulk (grain) conductivity of 4.86 × 10-5 S cm-1 at 300 °C and 8.1 × 10-2 S cm-1 at 600 °C, as determined from the grain resistance of Pt-coated pellets measured in air. The BYSO-based cell further exhibited a cell-derived grain conductivity of approximately 0.10 S cm-1 at 550 °C under fuel-cell operating conditions, a high-power density of 587mWcm-2 at 550 °C under H2/air, and a high open-circuit voltage (≥1.00V). Atomic-scale scanning transmission electron microscopy reveals local oxygen-deficient regions and Sm distributions that are predominantly consistent with substitutional incorporation. In contrast, some local Sm-intensity features suggest the possible presence of a minor octahedral interstitial Sm configuration. Such a configuration may locally perturb the oxygen sublattice and contribute to the enhanced transport behavior, together with the observed reconstruction of the {111} surface regions. First-principles calculations further indicate that Sm incorporation modifies the local structural and electronic environment of Bi3YO6, including the Sm–O coordination and electronic charge distribution, providing complementary insight into the experimentally observed transport behavior.
Lead-free Ce doped BNBT piezoceramics were studied to investigate the influence of Ce replacement on ferroelectric, dielectric, energy storage properties. Incorporating Ce disrupted long-range ferroelectric pattern, enabling an enhanced relaxor state characterized by decreased coercive field (Ec = 11.5 kV/cm) and suppressed remanent polarization (Pr) and this relaxor-like conversion is suggested to be mediated by donor/acceptor doping behaviour and associated oxygen vacancies (VO∙∙), that disorder polar nanoregions (PNRs). A high normalized strain of Sₘₐₓ/Eₘₐₓ = 395 pm/V due to field-induced phase transitions and high recoverable energy density (Wrec) 0.68 J/cm3 was achieved for x = 0.03. However, the compositional shift to x = 0.04 yields the energy efficiency (η) of 82%. Dielectric properties displayed that Ce incorporation broadened the peaks at dielectric maxima (Tm) and the dielectric constant was decreased. The strain and energy efficiency in modified BNBT ceramics providing key insights for defect-engineering lead-free capacitors and energy storage materials.
