This study systematically investigates the effects of grinding parameters (e.g., grinding speed, feed rate) and subsequent heat exposure (at varying temperatures and durations) on the surface and subsurface recrystallization behavior of a nickel-based single crystal superalloy processed by robot-assisted grinding. Multiscale characterization techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD), were employed to analyze the morphology, elemental distribution, crystallographic features, and defect evolution of recrystallized grains. The results demonstrate that: (1) The recrystallization type and thickness are jointly regulated by heat exposure temperature and time. Under identical temperatures, the recrystallization layer thickens with prolonged exposure, while distinct recrystallization morphologies emerge at different temperatures. (2) The recrystallization thickness exhibits a nonlinear relationship with grinding speed, initially increasing and then decreasing as the grinding speed rises. (iii) EBSD analysis reveals that recrystallized grains are predominantly submicron-sized (< 1.5 μm), with boundaries dominated by low-angle grain boundaries and minor twin boundaries. High densities of geometrically necessary dislocations (GND) and significant grain reference orientation deviation (GROD) angles observed in the grinding-affected zone confirm that plastic deformation storage energy serves as the primary driver for recrystallization.
Magnesium–zinc alloys in the homogenized condition with various grain sizes (D) and different Zn contents in the α-Mg matrix (xZn) were obtained by adding different amounts of Zn, Ca, and Sr and two-step homogenization treatment. It was revealed that with increasing Zn content, D decreases; while xZn increases upon homogenization. Moreover, Ca and Sr addition leads to grain refinement and change in the possibility of secondary phase dissolution, affecting xZn. Regarding mechanical properties, the main hardening/strengthening effects were characterized as grain boundary strengthening and solid solution via Zn dissolution. As a result, the classical Hall-Petch relationship was unable to present the grain size dependency of hardness (H) and yield stress (YS). To address this issue, the solid solution effect was incorporated into the Hall-Petch relationship, showing improved agreement with the measured H and YS. Accordingly, the modified Hall-Petch formulae of H = 32 + 6xZn + 66.5/√D and YS = 26.2 + 10.54xZn + 159.6/√D were proposed and verified based on the leave-one-out cross-validation (LOOCV) approach. In summary, this work provided preliminary empirical correlations valid for the investigated alloy set and homogenization conditions.
The article develops a novel comprehensive multi-directional and multi-physics framework for analyzing the coupled vibro–electro–magnetic response of advanced smart plate structures. It investigates the porosity-dependent vibration behavior of multi-directional functionally graded magneto-electro-elastic (MFG-MEE) porous plates subjected to externally applied magneto-electrical potentials. The kinematic relations are derived using a refined four-variable shear deformation plate theory. The magneto-electro-elastic properties of the MFG plate varied smoothly along the three directions (length, width, and thickness), are estimated by using the modified power-law rule. Two distinct porosity distribution patterns are incorporated to characterize void and cavity variations through the plate thickness. The governing equations consist of six coupled partial differential equations with variable coefficients are derived. The differential quadrature method (DQM) is employed to discretize these equations, while the integral quadrature method (IQM) efficiently handles the variable coefficients. The accuracy of the proposed model and solution methodology is validated through comparisons with available results in the literature, yielding relative errors ranging from 0.01 to 4.7
This paper focuses on sandwich panels with stepped functionally graded material (FGM) layers and initial geometric imperfections, exploring their nonlinear transient behavior when placed on viscoelastic bases and subjected to sinusoidal forces. The three-layer composition involves a uniform core, with upper and lower FGM face sheets exhibiting a stepped thickness profile. The face sheets are divided into two segments of distinct thicknesses along both the length and width directions, achieving optimal stiffness enhancement while maintaining a constant total thickness. The FGM face sheets exhibit thickness-dependent material properties following a power-law distribution. Utilizing the third-order shear deformation theory (TSDT) and incorporating initial geometric imperfections along with von Kármán geometric nonlinearity, a theoretical model was developed. The governing equations are solved via the Galerkin and Runge–Kutta methods, with model accuracy validated against existing literature and finite element analysis results. In the numerical analysis, four different geometric configurations of the sandwich plates are selected to examine the influence of key parameters, including initial geometric imperfections, aspect ratio, thickness ratio, damping coefficient, load amplitude, load duration, and power-law index, on the transient response of the sandwich plates. The findings of this study provide a theoretical basis for the dynamic design and optimization of stepped FGM sandwich structures with initial geometric imperfections.
Laser metal deposition (LMD) of AlSi10Mg alloy often leads to coarse columnar dendrites, a continuous network of eutectic Si phase, and residual porosity, which degrade mechanical properties and corrosion resistance. In this study, friction stir processing (FSP) was applied to modify the LMD‑fabricated AlSi10Mg alloy. The effects of FSP on the microstructure evolution, phase distribution, elemental homogeneity, microhardness, wear resistance, and corrosion resistance were systematically investigated. The results show that FSP induces intense dynamic recrystallization, transforming the coarse, textured columnar grains into fine, uniform equiaxed grains with an average size reduced from 65.15 μm to 3.26 μm. The continuous network of eutectic Si is broken and redistributed into fine, dispersed particles, and elemental segregation (especially Si) is largely eliminated. These microstructural changes lead to a significant increase in microhardness (from 80 HV0.2 to 105 HV0.2), a 46
