A machine learning method was used to uncover interaction mechanisms between substitutional and interstitial solutes in metals, using binding energy as the indicator of interaction strength. By applying classification and regression algorithms, both the sign (indicating attraction or repulsion) and magnitude of binding energy were investigated. SHapley Additive exPlanations (SHAP) analysis reveals that the atomic volume of substitutional solutes is the most influential factor, followed by the number of unpaired electrons in the host metal and the electronegativity of substitutional solutes. SHAP-driven visualizations elucidate the decision-making process of the model, providing multi-scale insights from global patterns through local interactions down to individual sample predictions. This approach delivers intuitive, quantitative representations of feature contributions in both magnitude and direction, surpassing traditional analysis methods. Moreover, the model generates thousands of new binding energy predictions with minimal computational overhead, significantly enhancing computational efficiency.
To improve the high-temperature damping performance of aluminum alloys, the ZA27 alloy as a reinforcement phase was integrated into the 6061 Al alloy by friction stir processing (FSP) to develop ZA27/6061 aluminum matrix composites with enhanced high-temperature damping capacity. The results demonstrate that FSP effectively fuses the ZA27 reinforcement phase with the 6061 Al alloy, resulting in no interfacial reactions. The introduction of the ZA27 reinforcement phase leads to a reduction in the average grain size and an increase in the dislocation density within the composites. At about 275 °C, an internal friction (IF) peak was observed in the ZA27/6061 aluminum matrix composites. The IF value is 933.9% higher than that of the 6061-FSP Al alloy. The improved interfacial damping resulting from grain refinement, along with the inherent superior damping characteristics of the reinforcement, significantly enhances the high-temperature damping ability of the ZA27/6061 aluminum matrix composites.
To resolve the strength–ductility trade-off in Mg/Al composites, a mechanical-ultrasonic vibration assisted rolling (M-UVAR) technique was developed. The M-UVAR composites exhibit an interfacial bonding strength exceeding 58.6 MPa, with a 22.65% increase in tensile strength and a 120% improvement in elongation compared to traditional rolling (TR) composites. The TR composites display a 10 μm transition layer of Mg2Al3 and low-angle grain boundaries. However, the M-UVAR composites develop a 42 μm gradient microstructure consisting of Mg−Al solid solution, stacking faults, high-angle grain boundaries and ultrafine grains. A gradient structure is formed at the interface with increasing density toward the interface. This structure pins dislocations, restricts their motion, and promotes stacking, significantly enhancing strength. Simultaneously, the gradient microstructure improves stress/strain distribution, while ultrasound-induced defect elimination creates space for geometrically necessary dislocations, jointly boosting ductility. Ultimately, unique interfacial microstructure of M-UVAR achieves synergistic improvement in the strength and ductility of the composites.
The rolled (R sample) and extruded (E sample) AZ31 alloys show different texture characteristics, exhibiting a strong basal texture and a transverse direction-split texture, respectively. The increased crystallographic orientation heterogeneity in the E sample enhanced resistance to slip transfer, leading to a more pronounced slip accumulation at the grain boundaries between adjacent grains. This resulted in a higher hetero-deformation induced (HDI) stress in the E sample compared to the R sample. The enhanced yield strength observed in the E sample can be ascribed to the elevated Hall−Petch slope value, which was a consequence of the reduced geometrical compatibility factor. Meanwhile, more significant HDI strengthening and hardening effects synergistically improved both strength and ductility. Notably, high grain boundary misorientation angle contributed to the activation of non-basal slips, thereby alleviating local strain concentration near the grain boundary and improving the work hardening ability.
Grain boundary (GB) characteristics in relation to texture development were investigated in an extruded Mg−Zn−Gd alloy subjected to isothermal annealing at 400 °C for 5−155 min. Quasi in-situ electron backscatter diffraction (EBSD) was employed to analyze grain growth (GG), grain rotation, and GB character evolution. GG was found to proceed via two distinct mechanisms: nucleation at triple junction followed by subsequent growth, and GB migration governed by the Burke–Turnbull mechanism. The rotation angle of (0001) basal pole ranged from 31° to 40°, contributing to the observed non-basal texture. Misfit strain (δ) associated with various coincidence site lattice (CSL) boundaries was evaluated, showing that the length fractions for Σ7, Σ13b and Σ45a boundaries decreased in the isothermal annealing due to their higher δ values, while those for Σ9, Σ21a and Σ43b boundaries increased. Grain growth kinetics was evaluated after isothermal annealing and grain growth exponent was also determined. Collectively, these findings demonstrate that GB characteristics significantly influence texture evolution by promoting energetically favorable boundary configurations.
The effect of α lamellae configuration on recrystallization uniformity in TC18 alloy was systematically investigated. The results indicated that with increasing the thickness of α lamellae, the β grain size uniformity factor (statistics standard deviation) exhibits a tendency of decreasing and then increasing. The mechanism of microstructural homogeneity regulation through the interplay between α dissolution and β recrystallization nucleation and growth was elucidated. When the α lamellae are thin, β recrystallization nucleation primarily occurs through grain boundary-induced boundary migration mechanism, characterized by unidirectional nucleation from high-strain to low-strain regions, resulting in excessive growth of certain β grains. However, the thick α lamella results in asynchronous processes of β recrystallization nucleation and growth near the grain boundaries and within the grains, ultimately leading to deteriorated β grain size uniformity.
The microstructure of Ti-55511 alloy in a wide annealing temperature range of 600−900 °C was obtained by gradient heat treatment. The annealing microscopic mechanism map reflecting phase composition and the homogeneity of grain size was constructed. When the temperature exceeds 875 °C, the annealing microstructure is a single-phase structure of β phase. When the annealing temperature is 800−875 °C, a small amount of α lamellar structure is precipitated in the β grains. When the annealing temperature is 650−800 °C, the αGB phase precipitates at the β grain boundary. When the annealing temperature is 600−650 °C, the content of the α phase is high but there is no αGB phase. The sample annealed at 750 °C for 120 min has good matching of strength and plasticity, with a yield strength of 1197 MPa and a true fracture strain of 0.31. The annealing microstructure has the best homogeneity degree of β grain size. The α lamellar structure can hinder the dislocation movement, and its grain boundary strengthening effect contributes 207 MPa to strength.
The effects of varying pre-torsion amounts (35 and 41 N·m) on the tensile properties, deformation mechanisms, and fracture behavior of Ti-55531 alloy with a bimodal microstructure were investigated using a combined pre-torsion and tension loading approach. The findings reveal that pre-torsion deformation prior to tension enhances the activity of plastic deformation mechanisms by promoting dislocation slip and altering grain orientation. Under uniaxial tensile loading, the αp phase activates multiple prismatic slip planes without significant interaction. Conversely, under pre-torsion (35, 41 N·m)−tension loading, the αp phase predominantly induces interactions among multiple slip planes within the prismatic slip system, resulting in an increased density of slip lines as the pre-torsion amount increases. Furthermore, pre-torsion promotes the formation of high-density twins within a single αs lath following tensile deformation.
The microstructural evolution, texture development, and mechanical properties of Ti60 linear friction welded joints were systematically investigated under varying welding pressures (32, 64, and 96 MPa). Continuous dynamic recrystallization occurs in both the weld zone (WZ) and thermo-mechanically affected zone (TMAZ), with increased welding pressure leading to refined recrystallized β grains and reduced joint dimensions. The WZ exhibits transformation from parallel lamellar α to acicular martensitic α' with basket-weave morphology. Texture analysis reveals pressure-dependent characteristics, with maximum intensity (11.27) observed at 64 MPa in the WZ. Enhanced mechanical properties result from multiple strengthening mechanisms: strain hardening and phase transformation strengthening in the TMAZ, coupled with grain refinement and phase transformation strengthening in the WZ. While joints maintain equivalent tensile strength to the base material, their elongation increases with welding pressure (8.0%, 9.3%, and 9.7% at 32, 64, and 96 MPa, respectively), correlated with reduced TMAZ and WZ widths.
The solidification structure of nickel-based single crystal superalloy was systematically investigated by the combined methods of scanning electron microscopy, electron probe microanalysis, site-specific sampling, spherical aberration-corrected scanning transmission electron microscopy and super energy dispersive spectroscopy. The results show that four distinct solidification microstructures, dendritic core, interdendritic region, coarse γ′ phase and a network-type (NT) γ–γ′ eutectic, are formed during the process of directional solidification. The NT γ–γ′ region exhibits low γ/γ′ interfacial misfit and minimal segregation, showing exceptional stability against dissolution during heat treatment. In contrast, the coarse γ′ phase displays high misfit, severe segregation, and dense quadrilateral dislocation networks at interfaces, promoting dissolution and re-precipitation of γ′ phase.
The effects of surface mechanical attrition treatment (SMAT) on pure copper, with treatment durations ranging from 15 to 60 min, were investigated, focusing on surface characteristics and current-carrying tribological behavior. The current-carrying tribological behavior was examined using reciprocating microscale sliding tests under loads of 50 and 200 mN with an applied voltage of 5 V. The results show that sufficient SMAT not only produces nanocrystalline structures that improve the surface hardness of copper but also develops (111) textures and promotes the formation of finely-dispersed copper oxides on the surface layer. These microstructural evolutions synergistically contribute to optimal current-carrying tribological performance in the sample treated for 60 min at a load of 50 mN. Compared to the untreated sample, the friction coefficient, wear rate, and electrical contact resistance (ECR) of the 60 min SMAT-treated sample are reduced by 6.5%, 47.1%, and 9.3%, respectively, and the stability of current transmission is improved by 4.3%.
The thermo-mechanical response and failure precursors of granite and granodiorite subjected to heat treatments at 100–300 °C, followed by either natural cooling or rapid water-cooling, under uniaxial, biaxial, and Brazilian splitting tests were examined. Acoustic emission (AE) monitoring was used to track amplitude (A), the ratio of initial rising angle to average frequency (RA/AF), and the ratio of energy to ringing counts (E/C) parameters, and their evolution was analyzed using variance, autocorrelation coefficient, and entropy to identify early-warning signals. The results indicate that the combined variation of these statistical indicators successfully captures the transition from stable crack propagation to imminent failure. Natural cooling decreases system disordering, whereas rapid water-cooling intensifies AE activity and energy release due to residual thermal stresses. These findings establish a multi-parameter AE-based framework for evaluating instability in thermally damaged crystalline rocks.
Uniaxial compression tests combined with acoustic emission (AE) monitoring were conducted on the sandstone and concrete specimens to measure the physical and mechanical properties and analyze the damage evolution after heating test. A modified thermal-mechanical statistical damage constitutive model was established by K-means++ clustering algorithm for determining the proportion of tensile and shear cracks in AE data and for defining the new tensile and shear mechanical damage factors of the Weibull distribution. This model is verified to be valid by good agreement with the experimental results.
To optimize pulp rheological properties and enhance fine spodumene recovery, sodium p-styrene sulfonate (SPS) was employed as a rheological modifier. Through rheological analysis, flotation tests, and EDLVO theoretical calculations, the mechanism of SPS in regulating pulp rheology and improving spodumene flotation performance was systematically elucidated. The results show that, as the size of mineral particles in the slurry decreases, both the shear yield stress and the apparent viscosity of the slurry increase, which can negatively affect the flotation recovery of spodumene. However, after adding SPS, the zeta potential of fine spodumene particles decreases from −48.93 to −50.33 mV, while that of feldspar particles decreases from −65.33 to −75.14 mV. The repulsive force among 10 μm particles increases from 4.3 to 7.1 nN, whereas the apparent viscosity decreases from 1.069 to 0.861 mPa·s. The strengthened electrostatic repulsion between spodumene and feldspar particles effectively reduces pulp viscosity and shear yield stress. These modified rheological characteristics create favorable conditions for improved flotation performance of fine spodumene, ultimately enhancing separation efficiency.
The zinc removal kinetics from the zinc-bearing dust pellets was comparatively investigated using conventional heating reduction (CHR), atmospheric microwave-heating reduction (AMR) and vacuum microwave-heating reduction (VMR) processes. Key operational parameters, including vacuum environment, microwave-heating, reduction time and reduction temperature, were evaluated for their effect on zinc removal efficiency. The results show that vacuum and microwave-heating conditions significantly lower the reduction temperature, shorten the reduction time, and lessen the reductant dosage compared with the CHR process. The kinetic model fitting results show that the zinc removal model of VMR process is the Avrami−Erofeev second-order chemical reaction model. The apparent activation energies of the CHR, AMR and VMR processes are 93.15, 60.52 and 18.69 kJ/mol, respectively.
An alkaline autoclave dissolution method was developed to directly extract LiOH from α-spodumene in NaOH−Na2SO4−CaO system. Approximately 90.3% Li, 10.27% Si, and 9.62% Al were leached under optimal conditions: ore to CaO mass ratio of 1:1, liquid-to-solid ratio of 14 mL/g, NaOH and Na2SO4 mass concentrations both of 15% at 280 ℃ for 3 h. Notably, the addition of Na2SO4 was found to selectively replace Li+ while simultaneously reduce NaOH consumption. Kinetic analysis was also provided further insight into the dissolution behavior of α-spodumene in this system. This innovative autoclave process can eliminate the energy-intensive high-temperature calcination for phase transformation, and enables the direct preparation of LiOH·H2O from α-spodumene.
