Thermal oxidation was employed as a method to enhance the wear resistance of two novel TiZrAlV alloys. The obtained oxidized coatings, primarily composed of TiO2, ZrO2, Al2O3, and Ti2ZrO6, showed compositional variations influenced by Ti/Zr ratio. Oxidation kinetics revealed distinct kinetic behaviors: the T30Z alloy followed a linear model, whereas the T47Z alloy exhibited parabolic model. Furthermore, the specific wear rate of the T30Z alloy initially decreased from 32.18×10−4 to 22.21×10−4 mm3/(N·m) during short durations, but increased after 24 h due to coating performance degradation. In contrast, the T47Z alloy showed a consistent improvement in wear resistance under all conditions, achieving a minimum specific wear rate of 20.87×10−4 mm3/(N·m). Regarding wear mechanisms, the T30Z alloy exhibited both abrasive and adhesive wear, except after 1 h of oxidation. In comparison, the oxidized coating on the T47Z alloy effectively suppressed adhesive wear, throughout the durations, except 36 h of oxidation.
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.
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.
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.
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.
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.
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.
To explore the mechanism of chalcopyrite bio-oxidation in acid mine drainage (AMD), a two-factor, three-level chalcopyrite bio-oxidation experiment was designed to assess the effects of visible light and pyrrhotite, which are common environmental factors that influence AMD. Bio-oxidation results, mineral surface morphology, mineralogical phase, elemental composition and electrochemical analyses revealed that visible light and pyrrhotite promoted chalcopyrite bio-oxidation, facilitating enhanced copper release and iron/sulphur oxidation and dissolution. The results demonstrated that visible light contributed to maintaining suitable oxidation–reduction potential and eliminating passivator S0. Meanwhile, pyrrhotite enhanced mineral redox activity of chalcopyrite and photoelectron transfer, thus promoting chalcopyrite leaching. In addition, a considerably enhanced interaction between Acidithiobacillus ferrooxidans and chalcopyrite facilitated ferrous iron oxidation, iron/copper release and sulphuric acid generation.
First-principles calculations were employed to investigate the effects of microalloying element X (X = Yb, Er, Sc, Zr, Hf) interactions on the formation of L12 phases in aluminum conductor during aging. The evolution of L12-Al3X core−shell phase was examined. The analysis of interactions among solute atoms reveals a preference for elements to bind at the second nearest neighbors (2NN) distance. Particularly, Yb and Er are found to effectively attract elements to form clusters, with Sc showing a comparatively weaker attraction. Among the tri-solute combinations, Yb−Er−Zr exhibits the strongest mutual attraction. When the solute is segregated on the surface of phase, the segregation energy of remaining solute at the Al3X/α-Al interface increases gradually with decreasing the element diffusivity. Notably, the segregation energies at the Al3Yb/α-Al and Al3Er/α-Al interfaces are similar and relatively low. The values of segregation energies at the interfaces are primarily determined by the solute bonding with surrounding atoms. The interface energy of Al3X/α-Al is negatively correlated with the element diffusivity. The core−shell interfaces, such as Al3Er/Al3Hf, Al3Yb/Al3Hf, Al3Zr/Al3Er, and Al3Zr/Al3Yb, exhibit high interface stability, which is determined by the chemical bond strength between the atoms of microalloying elements at the interface.
To overcome the limitations of low activity of single-metal sites and suboptimal interface structures of porous carbon-derived electrocatalysts, a nitrogen-doped carbon-coated CuCo nanoparticle (CuxCoy−NC) catalyst was synthesized using a straightforward grinding method followed by high-temperature pyrolysis. The introduction of CuCo bimetallic sites plays a crucial role in enhancing the intrinsic catalytic activity by diversifying the active sites and optimizing the adsorption energy of oxygen intermediates. Particularly, when the Cu/Co mass ratio is 1:1, the formation of thin-walled carbon nanotubes effectively exposes the embedded metal active sites and refines the interface structure of the porous carbon matrix. As a result, the optimized CuxCoy−NC (1:1) catalyst demonstrates exceptional electrocatalytic performance for the oxygen reduction reaction. This enhancement enables the assembled zinc−air batteries to achieve an impressive discharge specific capacity of 812 mA·h/g at 25 mA/cm2.
The differences in surface chemical composition among copper,lead,and zinc concentrates,as well as flotation residues obtained from the flotation of cyanide tailings,were investigated,using time-of-flight secondary ion mass spectrometry(ToF-SIMS)and X-ray photoelectron spectroscopy(XPS).XPS analysis revealed that oxidation of metal and sulfur ions on mineral surfaces induced by cyanide leaching diminished adsorption sites for flotation collectors.ToF-SIMS analysis revealed the surface composition differences of flotation concentrates and residues.Cyanide adsorption onto sulfide mineral surfaces during cyanide tailings leaching was a primary factor limiting the selective adsorption of flotation reagents in the flotation process of cyanide tailings.Additionally,dissolved metal ions from sulfide minerals during cyanide leaching were non-selectively adsorbed onto all mineral surfaces,weakening the boundaries of target minerals and thereby impeding effective flotation separation of sulfide minerals.
The shear property and fracture behavior of ZnSnCuNiAl/Cu solder joints were experimentally investigated under varying aging conditions and strain rates.The results demonstrate that higher aging temperatures can accelerate the diffusion of Cu atoms within the solder,leading to faster growth of intermetallic compounds(IMCs).Furthermore,extended aging durations result in a larger volume of IMCs.Shear tests reveal that the shear strength of the solder joint decreases as the thickness of the IMCs increases,highlighting the detrimental effect of excessive IMC formation on joint integrity.To evaluate the strain rate sensitivity of the solder joints,shear tests were conducted at different strain rates.The results indicate that the shear strength increases with higher strain rates,rising from 21.32 MPa with lower strain rates to 25.98 MPa with higher strain rates.The strain rate sensitivity index was calculated to be 0.052,confirming a positive correlation between strain rate and shear strength.At low strain rates,the solder exhibits internal ductile fracture,suggesting sufficient time for plastic deformation prior to failure.However,as the strain rate increases,the fracture location progressively shifts toward the interface between the solder and the IMCs,resulting in a mixed fracture mode characterized by both ductile feature and brittle feature.
Aiming at developing Mg alloys with good strength and ductility, an inverse temperature field equal channel angular pressing (ITF-ECAP) technique was proposed to realize the severe plastic processing of Mg−8Bi−1Al−1Zn (BAZ811, wt.%) alloy at low temperature of ~80 °C. As a result, a microstructure consisting of ultrafine grains having an average grain size (AGS) of ~506 nm and fine grains with an AGS of ~1.36 μm was constructed in BAZ811 alloy through 4-pass ITF-ECAP processing. Additionally, a large amount of nano-sized Mg3Bi2 phase precipitated during ITF-ECAP processing, and the micro-scale Mg3Bi2 particles were greatly refined. Furthermore, the ITF-ECAPed BAZ811 alloy exhibits an ultra-high strength−ductility synergy with yield strength and elongation of (381.5±4.2) MPa and (21.4±1.6)%, respectively. High strength stems from grain boundary, precipitate, and dislocation strengthening; good ductility arises from high intergranular strain coordination and weak texture plasticization.
The impact of cyclic heat treatment and acid etching on microstructure and corrosion performance of AA7075 was investigated.The microstructure of the alloy was characterized by EPMA,SEM and TEM,and the corrosion resistance of the alloy was studied by intergranular corrosion test.The results show that driven by continuous thermal energy and content gradient generated by the cyclic heat treatment and acid etching,Mg atoms in the surface layer of AA7075 continuously cross grain boundaries.Finally,a compositional gradient layer with a thickness of 185 μm is formed.The surface layer of AA7075 after the dealloying treatment demonstrates reduced intergranular corrosion susceptibility,which is due to low anodic and discontinuously distributed grain boundary precipitates in the dealloyed surface layer.
A crystal plasticity theory was coupled with a phase-field model to investigate the regulating effect of initial lattice misfits on the kinetics evolution and creep properties of Ni-based superalloys. The quantitative characteristics of the γʹ-(Ni, Co)3(Al, Ta) phase, including morphology, particle size, element partitioning, rafting fracture, and plastic strain evolution, were systematically elucidated in a model Ni−12.2Al−6Co−2.5Ta (at.%) superalloy at 1273 K. The results reveal that reducing the initial lattice misfit between the γ and γʹ phases promotes the partitioning of Al and Ta into the γ matrix and Ni into the γʹ phase, resulting in a higher γʹ volume fraction and slower coarsening rate in the alloys. The γʹ phase undergoes coalescence and coarsening at the primary creep stage, and dissolution and fracture at the secondary creep stage. Alloys with larger initial lattice misfit exhibit higher creep strain, faster raft degradation, and shorter creep life. These findings provide insights for designing high-performance superalloys by optimizing lattice misfits.
To improve the efficiency of gold extraction and address environmental pollution issues associated with conventional cyanide processes,a novel process was proposed to concentrate gold stepwise by iron matte and Bi-alloy.Firstly,theoretical analysis was conducted to confirm the feasibility of the new process.Three Bi-containing agents were selected to enhance gold capture in iron matte smelting.Subsequently,the effects of agents and Bi content on gold recovery rate in iron matte smelting were investigated.The gold content of slag decreases to 0.10 g/t,with a gold recovery rate of 99.53%.The distribution of Bi in iron matte is beneficial to the gold recovery.Furthermore,molten reverse extraction was conducted,thus resulting in a gold-enriched alloy with a gold content of 182.47 g/t.Finally,the entire process experiment was conducted to recycle iron matte and increase gold content in gold-enriched alloy.The gold content of gold-enriched alloy reached more than 400 g/t.
Multi-directional forging at 450 °C combined with rolling at 300 °C and 470 °C was applied to a 7050 aluminum alloy prior to heat treatment. The effects of rolling temperature on the microstructure of the alloy were analyzed using optical microscopy, X-ray diffraction, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. After solution treatment, the average grain size of the alloy measured from high-angle grain boundaries was approximately 20 μm, compared to 100 μm before forging. After artificial aging, the yield strength, ultimate tensile strength and elongation after fracture of the samples rolled at 300 °C were (609.9±5.5) MPa, (662.4±1.7) MPa and (18.5±1.2)%, respectively. In the case where the alloy was rolled at 470 °C, the corresponding values were (592.7±4.2) MPa, (641.0±3.9) MPa and (18.7±0.9)%, respectively.
This study aimed to enhance the mechanical properties of Al−Li alloys through alternating magnetic field (AMF)-assisted microstructure optimization. During heat treatment, the alloys were exposed to AMF (0.06 T) to systematically study the microstructure, precipitate evolution, and mechanical properties of the alloys. Compared to conventional treatment, at 160 °C and 24 h, AMF increased tensile strength from 517.6 to 523.3 MPa and yield strength from 452.0 to 465.6 MPa, despite a minor elongation reduction (from 7.8% to 6.1%). Microstructural analysis demonstrated that the AMF promoted a more uniform distribution and refinement of the precipitate while inhibiting precipitate coarsening, thereby improving the alloy strength. Under the conditions of 160 °C and 60 mT AMF for 24 h, the Al−Li alloy achieved optimal mechanical performance: the tensile strength reached 523.3 MPa, the yield strength was 465.6 MPa, and the elongation was 6.1%.
