In order to address the poor presplit blasting effect on the final slope of the Yulong Copper Mine in Xizang Autonomous Region, the engineering applicable ranges of parameters such as decoupling coefficient, borehole diameter, linear charge density and hole spacing were calculated in consideration of the combined effects of explosion-generated gases and air shock waves, and the presplit blasting parameters were also optimized by performing orthogonal experiment. The results indicate that with a borehole diameter of 120 mm, a linear charge density of 800-1 000 g/m and a hole spacing of 0.9 m, the half-borehole rate after blasting exceeds 95%, the unevenness between adjacent holes is much less than ±5 cm, and the slope gradient deviation is less than ±2°, forming a continuous and regular presplit surface. This confirms the engineering applicability of the theoretically calculated parameter ranges.

A new type of discontinuous mining system for deep-sea polymetallic nodules was proposed, consisting of collecting seafloor ore, conveying to buffer by flexible hose, and high-speed lifting of buffer. Then, the design and key equipment selection were carried out for the collecting system, flexible hose conveyance system and buffer lifting system for comprehensively lifting 100 t/h of ores at water depth of 5 200 m in the Minmetals' Contract Area. Furthermore, flexible hose configuration and load characteristics, as well as cable load dynamics during buffer lifting were all analyzed by hydrodynamic simulation. It is shown that with the flexible hose equipped with 18 buoyancy blocks, minimum bending radius of 1.6 m and a maximum tension of 4.98 kN, the whole mining system can satisfy requirements for the minimum bending radius and safe load capacity. During high-speed lifting of buffer, the cable can have the safety factor of comprehensive stress up to 5.22-6.03, exceeding the safety factor stated in national standard. These findings validate the reliability of this new type of deep-sea discontinuous mining system.

Constitutive models of HJC and RHT for different in-situ stress conditions were established by adopting ANSYS/LS-DYNA software, and the effects of blasting on effective stress and rock damage in different constitutive models were analyzed comparatively. The results show that the effective stress variation in the HJC model is more consistent with practical scenarios, while the rock damage in the RHT model can better reflect practical conditions. In-situ stress has a minor impact on effective stress in regions close to blast holes but a significant influence on effective stress in areas farther away. Additionally, in-situ stress has a smaller effect on rock damage in the HJC model, but substantially affects the damage variables in the RHT model.

Aiming at addressing the difficulty in selecting parameters for the support vector machine (SVM) model in predicting slope safety factors, a Newton-Raphson Backtracking Optimization (NRBO) algorithm was optimized to assist the SVM model in rapidly selecting appropriate hyperparameters. The NRBO algorithm was improved by introducing a dynamic opposition-based learning strategy, horizontal and vertical crossover strategies, and a modified adaptive coefficient calculation formula, so as to construct an INRBO-SVM model for predicting slope safety factors. Six factors, including bulk density, cohesion, internal friction angle, slope angle, slope height and pore water pressure ratio, were selected as model inputs, with the safety factor as the output. The trained INRBO-SVM model, NRBO-SVM model, SVM model and RBF model were used to predict the safety factors of nine test samples. The results show that the INRBO-SVM model exhibits the best performance in safety factor prediction, with a correlation coefficient of 0.999 9, higher than those of the other models. Its root-mean-square error and mean absolute error are significantly lower than those of the other models. Engineering application results indicate that the prediction errors of the INRBO-SVM model for safety factors are all less than 10%, with most below 5%, confirming the accuracy and practical application value of the model in predicting safety factors.

In order to assess stability of the current multi-level mined-out areas in Qijiaojing iron mine in Subei County Bolun Mining Development Co., Ltd.of Western Mining Limited Company, the mine excavation process was simulated with FLAC^3D software to mainly analyze the stress and displacement changes in the mined-out areas after multi-level excavation. The results indicate that the stress in the mined-out areas is predominantly compressive stress, which is primarily concentrated in the roof and pillars of the stope. The maximum compressive stress, approximately 20 MPa, is observed in the pillars of the mined-out area at the 2 150 m level. It is found that the mind-out area has the maximum settlement of 20.30 mm and the maximum horizontal displacement of 7.22 mm, being satisfactorily stable. However, long-term exposure of large-scale mined-out areas may lead to deformation and collapse of pillars. Therefore, regular inspections and reinforcement measures should be taken for the pillars during subsequent production processes.

The south slope of the Jingxi-Barak mining area of Xinjiang Jinchuan Mining Industry was taken for study. As for the issues of weakening mechanical parameters of slopes after an earthquake and the stability assessment of slopes under aftershocks, a BP neural network model optimized by the crow search algorithm (CSA-BP) was proposed for the inversion of mechanical parameters of slopes after an earthquake. The stability of slopes with dangerous rock mass under aftershocks was evaluated by using the discrete element method. The results show that the CSA-BP model can quantitatively reveal the weakening characteristics of rock masses through the inversion of mechanical parameters. Under aftershock of a magnitude 5 earthquake, significant displacement occurs in the tuffaceous sandstone in the middle and upper parts of the slope, with horizontal (x-direction) displacement far exceeding vertical (z-direction) displacement, indicating that slope instability is dominated by horizontal sliding. The CSA-BP model can accurately identify high-risk zones through a parameter-dynamic coupling mechanism, providing theoretical support for slope protection after earthquakes.

Ultra-fine iron ore tailings were modified through thermal activation, and then together with some waste rock were taken for mixed calcination. With the mass ratio of iron ore tailings to waste rock, calcination temperature and calcination time as variables, and the compressive strength of specimens and the content of chemically bound water as the objectives for optimization, an orthogonal experiment was carried out to analyze the sensitivity and influence trends of each factor on the target values, and the hydration products of the cemented materials were also analyzed. The results indicate that with an increase in the mass of waste rock, the specimen compressive strength initially increases and then decreases. As the calcination temperature rises, the specimen compressive strength monotonically decreases. As calcination time is prolonged, the specimen compressive strength first decreases and then increases. In consideration of both calcination cost and material performance, an optimal calcination scheme is finally determined, including iron ore tailings and waste rock in a mass ratio of 7∶3, a calcination temperature of 800 ℃, and a calcination time of 2 h. Under these conditions, the 3-day, 7-day and 28-day compressive strengths of the specimens can reach 4.18, 6.36 and 9.87 MPa, respectively. The main hydration products of the cemented materials are calcium silicate hydrate gel, rankinite, ettringite and hydrotalcite.

The western No.2 mining area of a certain mine adopts the non-pillar sublevel caving in mining, and excessive wedge cut height in the 1 546 m sublevel leads to poor blasting effect. To address this problem, blasting with wedge cut was specially studied. Firstly, the rock parameters were calibrated based on the RHT constitutive model and the damage threshold of the rock was determined to be 0.4 by a fluid-structure interaction analysis with the LS-DYNA software. A comparative analysis of the cut blasting effects with different cut width shows that with the cut height fixed at 23 m, the effective damage rate of the rock presents a unimodal distribution with an increase in cut width. The optimal cut width is found to be 24 m, with which the effective damage rate of the rock can reach a peak value of 0.692 5. Based on these parameters, the on-site application of designed cutting scheme indicates that over 85% of blast-forming space can meet the requirement, presenting a reasonable fragment distribution of muck pile, with the angle of repose at approximately 40°.

As for a mine in Yunnan, the failure modes of surrounding rock in roadways buried at a depth of 1 500 m was analyzed by adopting a combination of theoretical analysis, in-situ monitoring and numerical simulation for exploring the variation law of surrounding rock stress. The results indicate that the surrounding rock in the main transportation roadway and the drift transportation roadway near the ore body at a depth of 1500 m predominantly belongs to Class Ⅰ and Class Ⅱ rock masses. The influence of stratum stability on the broken zone is greater than that of the roadway cross-sectional dimensions. Under the disturbances of surrounding rock stress, mining-induced stress and blasting loads, the stress in the arch corner of the roadway is higher than that in the side walls. Based on the failure modes of the surrounding rock, a support method combining rock bolts, steel mesh and shotcrete was proposed. The 3DEC numerical simulation results show that after support, the depths of the plastic zones in the side walls, roof and floor of the roadway are reduced by 0.5 m, 0.8 m and 0.6 m, respectively.

In a Hunan polymetallic ore concentrator, the tailings with CaF₂ grade of 26.56% exhibit certain economic value. However, due to the influence of residue reagents in the upstream processing of main tungsten-molybdenum-bismuth minerals and the interference of calcium-bearing gangue, it is extremely difficult to recover fluorite from the tailings. A process consisting of selective regrinding, tailings discarding by high intensity magnetic separation, and fluorite flotation was adopted with a new reagent NH-1 as activator of fluorite, CY-63 as collector of fluorite, SWG+SZY as depressant of silicate and micro-fine gangue, and CYAB as depressant of calcareous gangue. As a result, fluorite concentrate with CaF₂ grade of 90.50%, CaCO₃ content of only 1.35% and CaF₂ recovery of 79.50% was finally reclaimed in the closed-circuit test. It is concluded that such tailings resources can be comprehensively utilized by adopting this process.

As for a gold-bearing pyrite from Hebei Province, the influence of four oxidants, including H₂SO₄, H₂O₂, HNO₃ and KMnO₄, on its floatability was investigated, and the adsorption of collectors on pyrite was also explored by infrared (IR) analysis and electrochemistry measurement. The flotation test shows that with H₂SO₄, H₂O₂ and HNO₃ as oxidants, moderate oxidation can promote the floatability of pyrite, while the oxidation of KMnO₄ can obviously depress the floatability of pyrite. The IR analysis shows that the effects of these four oxidants on pyrite-collector interaction are in the following descending order: HNO₃>KMnO₄>H₂O₂>H₂SO₄. The oxidation of KMnO₄ may passivate pyrite and reduce its floatability. Electrochemical analysis shows that H₂SO₄ and HNO₃ have obvious oxidation effects on pyrite. By increasing oxidant concentration, the double xanthate formed on pyrite due to its reaction with xanthate will be oxidized by H₂O₂ solution, and the hydrophobic layer on pyrite will be destroyed, leading to the decline of pyrite's floatability.

The parameters of lifter bars in the design of a Φ12.2 m×6.7 m semi-autogenous grinding (SAG) mill liner for the Las Bambas concentrator in Peru were optimized by employing discrete element method, and a quadratic regression model was constructed based on response surface analysis to investigate the effect of various factors on total collision energy and energy dispersion. The results indicate that lifter height has a significant impact on particle motion behavior, and it can alter drop height, particle trajectory and moving range, thereby impacting the collision energy during grinding process. The face angle and width of lifter can influence the distribution of collision energy by adjusting particle positions in the cascading and grinding zones. Based on a comprehensive consideration, the optimal lifter parameters are finally determined as follows: height of 380 mm, width of 100 mm, and face angle of 30°.

The separation process and the on-site equipment used for processing a copper-molybdenum bulk concentrate in Yunnan are systematically introduced. By improving the technical flowsheet and optimizing configuration, the processing capacity of Cu/Mo separation system can be increased from 25.00 t/h to 35.70 t/h, while the Mo grade and recovery are improved by 3.98 and 5.74 percentage points, respectively. Meanwhile, the power consumption can be reduced by 10.21%, and the unit production cost of Mo metal can be reduced by 7.06%, bringing a good economic benefit.

As for the molybdenum ores from Yichun Luming Mine, an m-order grinding kinetics model was used to explore the effects of four grinding aids, such as triethanolamine (TEA), triisopropanolamine (TIPA), polyacrylic acid (PAA) and polycarboxylic ether (PCE), on grinding kinetics of molybdenum ores. The results show that before addition of grinding aids, the proportion of the milled product in the size range of -0.074 mm increases significantly with the increase of the medium charge ratio, and the grinding kinetic parameters of m and k all increase; with the same medium charge ratio, the parameter of m increases and the parameter of k decreases as the grain size of milled product decreases. Comparatively, as for the samples milled with grinding aids of TEA, TIPA, PAA and PCE, the milling products in the size range of -0.074 mm increase by 6.19, 2.40, 3.62 and 1.89 percentage points, respectively. Compared to the system without grinding aids, an addition of TEA can lead to higher values of parameters of k and m, and larger particle size can result in great decline in the k value, while small particle size can bring a gentle k-grain curve, indicating the k value plays a dominant role at the initial grinding stage. After addition of grinding aids, the grains present improved dispersibility with significantly less agglomeration.

The influence and reaction mechanism of sodium humate as a depressant on the flotation of apatite, dolomite and calcite in sodium oleate system were investigated by performing single-mineral flotation test, adsorption test, Zeta potential measurement, infrared spectroscopy analysis and X-ray photoelectron spectroscopy analysis. The results show that sodium humate can strongly depress dolomite and calcite at pH of 7, but has less effect on apatite flotation. Sodium humate is weakly adsorbed onto apatite, but it can be adsorbed onto dolomite via chemical bonding, and also adsorbed onto calcite by the combined effect of hydrogen bonding and chemisorption. As a result, the variation in adsorption of sodium humate onto apatite, dolomite and calcite leads to its selective depression of the latter two minerals.

Surfactants of Span80 and Tween80 were adopted to emulsify diesel in an experiment. Based on the studies on effects of diesel microemulsion on the concentrate recovery rate by graphite flotation and fuel-saving efficiency, the optimal conditions for preparing diesel microemulsion were determined as follows: emulsifier's hydrophilic-lipophilic balance (HLB) value of 9, n-butyl alcohol as a co-emulsifier, and emulsifier and co-emulsifier in a mass ratio of 2∶1. Under these conditions, the diesel microemulsion can be prepared with an average particle size of 78.82 nm and uniformly dispersed, presenting excellent stability. Flotation experiments showed that the usage of diesel microemulsion could save 28.66% of oil. And the mechanism of interaction between diesel microemulsion and graphite reveals that diesel microemulsion can significantly reduce the surface tension of the pulp, thus increasing the contact angle of graphite, leading to a higher flotation recovery rate compared to the adoption of conventional diesel.

Although the annual production of low-concentration microfine-grained ilmenite in Pan-Xi region attains over 1 million tons, it is not conducive to adopt flotation process for the subsequent titanium selection due to the microfine particle size, large volume and low concentration of this ore. For this resource, comparative experiments were conducted based on two major flowsheets, including “SLon high-intensity magnetic separation + flotation” and “desliming using new type of cyclone+flotation”. The results show that the latter process flowsheet has a lower consumption of reagents, and the obtained titanium concentrate has better indicators, with a titanium concentrate grading 47.06% TiO₂ at 59.03% recovery with the yield of 20.22%.

Based on the optimization of flotation parameters of a low-grade spodumene ore from Sichuan, processing tests were conducted by adopting four flotation schemes to investigate their advantages and disadvantages. It is found that both the process of flotation with full-size range of ores followed by middling regrinding and the process of desliming followed by flotation and sequential returning of middlings are more advantageous than the conventional flowsheet of flotation with full size-range of ores followed by just sequential returning of middlings. It is shown that Li₂O recoveries by two processes can be increased correspondingly by 1.08 and 1.53 percentage points, and the second processing technique can bring a higher Li₂O recovery at 86.7%. However, the first processing technique can produce a higher quality lithium concentrate with a Li₂O grade of 5.76%.

To achieve the separation of arsenic and antimony from high-arsenic antimony-containing dust, a selective oxidation roasting process was employed with barium oxide as an antimony-fixing agent. The effects of oxygen partial pressure, roasting temperature, roasting time, and the dosage of antimony-fixing agent on the volatilization rates of arsenic and antimony from the dust were explored. The results indicate that with pure oxygen flow rate at 40 mL/min, addition of barium oxide at an amount of 2%, and roasting at 450 ℃ for 60 min, the volatilization rates of arsenic and antimony in the dust can reach 90.46% and 6.79%, respectively. It is shown that the volatile products contain 99.53% As₂O₃ and 0.26% Sb, thus effective separation of arsenic and antimony from high-arsenic antimony-contained dust antimony can be actualized.

Based on process mineralogy study, a processing technique consisting of atmosphere roasting and leaching with dilute sulfuric acid was proposed to separate a kind of mixed rare earth concentrate containing 48.23% REO. It is found that the phase composition of such concentrate is mainly composed of bastnaesite, monazite, apatite and fluorite, with rare earth elements primarily existing in bastnaesite and monazite. Under air/argon atmosphere roasting, phases of monazite, apatite and fluorite can remain stable, and phase transition is mainly attributed to bastnaesite reaction. In an air atmosphere, bastnaesite is transitioned in the following steps, CeFCO₃→Ce₇O₁₂→Ce₁₁O₂₀→CeO₂, while its transition steps in an argon atmosphere include CeFCO₃→Ce₇O₁₂, Th_0.5Ce_0.5O_1.84→CeOF. After roasting in an air atmosphere at 500 ℃ followed by leaching with dilute sulfuric acid, the leaching rates of F-REO and P-REO can reach 86.67% and 1.70%, respectively, while the process of roasting at 700 ℃ in an argon atmosphere can lead to the leaching rates of F-REO and P-REO at 75.97% and 13.33% respectively. And the leaching residues obtained from above-mentioned two different processes have F-REO and P-REO contents of 6.92%, 26.02% and 11.86%, 21.81% respectively, all dominated by monazite. It is concluded that this processing technique of atmosphere roasting followed by dilute sulfuric acid leaching can effectively achieve separation between bastnaesite and monazite.

The incineration slag of circuit board was doped with different proportions of copper concentrate, and then calcined at a high temperature to prepare oxygen carrier. The effects of doping amount of copper concentrate and calcination temperatures on the phase composition and morphology, as well as the oxygen absorption and desorption performance of the prepared oxygen carrier were all explored. The results indicate that CuFe₂O₄ is the main phase of the oxygen carrier, the formation of which can be improved by increasing the doping amount of copper concentrate and calcination temperature; the prepared oxygen carrier exhibits excellent lattice oxygen transfer capability; the mass weight of oxygen carrier in an air atmosphere increases by about 3% due to oxygen absorption, while the mass weight in a nitrogen atmosphere decreases by about 4% due to oxygen desorption.

A chrysoberyl-type beryllium ore from Xinjiang, containing 0.102% Be with quartz as the dominant gangue mineral, was taken in an experimental study on sulfuric acid leaching. According to the Box-Behnken experimental design principle, a multivariate regression equation was established by using response surface methodology (RSM) for three influencing factors of leaching effect, including liquid-solid ratio, leaching time and leaching temperature, as well as their interactions. Based on the test of significance of regression equation, the optimum process conditions were determined as follows: roasting temperature of 900 ℃, roasting time of 3 h, sulfuric acid concentration of 50%, liquid-solid ratio of 3.2∶1, leaching time of 4.8 h and leaching temperature of 90 ℃. Under these conditions, the Be leaching rate is predicted to be 89.73%, and an average value is 89.10% based on three parallel experiments, indicating that the established model is accurate. A kinetic model of leaching revealed that the leaching process was controlled by interfacial chemical reactions, with an apparent activation energy at 50.42 kJ/mol.

In order to investigate the reaction behavior of associated thallium sulfide in zinc concentrate during fluidized roasting, thermodynamic calculation and verification experiments were conducted for the oxidation process of thallium sulfide. Firstly, the volatilization of thallium chloride, thallium oxide, metallic thallium and thallium sulfide were analyzed based on data retrieval and calculation, and the volatilization of those four matters was determined in the following descending order: Tl₂O>TlCl>Tl₂S>Tl. Then, the equilibrium analysis and the calculation of Gibbs free energy change of the Tl₂S-O₂ system were conducted. It is shown that Tl₂S volatilizes violently in an inert atmosphere as temperature rises, and decomposes into Tl and sulfur vapor after temperature is above 1 000 ℃. However, in an oxidizing atmosphere, Tl₂S begins to generate a large quantities of Tl₂SO₄ after the temperature reaches 100 ℃, and a few of Tl₂S begins to decompose into SO₂ and Tl₂O after temperature is above 1 000 ℃. No interaction occurs between Tl₂S and ZnO. In the practical roasting process, Tl₂S is completely converted into Tl₂SO₄ and remains stable in the calcine at the temperature above 800 ℃, which can be intensively removed in the subsequent open-circuit of leaching and purification process.

Based on the analysis of patent application trend, major applicants and technological development in recycling of spent lithium iron phosphate batteries by leaching process, a list of key patents of mainstream technologies is presented. The results show that the number of patent applications for recycling of spent lithium iron phosphate batteries by leaching process has been steadily increasing since 2015, and oxidative acid leaching is the mainstream technology at present, with other technologies keeping in pace. However, some outdated technologies are being phased out.

A thermodynamic analysis based on HSC Chemistry software reveals the phase evolution of main metals in the production of nickel matte by sulfidation smelting of copper-nickel electroplating sludge, and the optimal process conditions for obtaining medium-grade nickel matte by sulfidation smelting were also analyzed. Theoretical calculation shows that the electroplating sludge with grades of Cu and Ni at 3.0% and 3.5% respectively is smelted at a temperature of 1 300 ℃, with calcium sulfate as a sulfurizing reagent under a smelting atmosphere with in a volume ratio of 60%-75%, and the actual usage of sulfur 1.6-2.0 times the theoretical value. It is expected that medium-grade nickel matte with Fe content less than 20% can be obtained, and the contents of Cu and Ni in the slag with S ratio in the preferred range can be less than 0.20% and 0.43% respectively. It is shown that recovery rates of Cu and Ni exceed 95% and 90% respectively, and the fixation rate of Cr in the slag is over 99.9%. According to the statistical results of production samples, the distribution behavior of Cu, Ni and Cr is basically consistent with the thermodynamic analysis results. This proves that the established mathematical model has good reliability and is of certain guiding significance for production.

A low-grade manganese carbonate concentrate was processed by adopting direct sulfuric acid leaching. The effects of leaching parameters on the leaching rates of manganese, calcium and magnesium were investigated, and changes in phase composition and microstructure before and after leaching process were also discussed. The results show that under the optimized conditions, including acid and ore in a mass ratio of 0.6, liquid-solid ratio of 4∶1, leaching temperature of 60 ℃, and leaching time of 3 h, the leaching rates of manganese and magnesium reach 99.36% and 83.97% respectively, while calcium is hardly leached out and mainly left in the residue as calcium sulfate.

Multiferroic BiFeO₃ ceramics were synthesized by chemical co-precipitation. The effects of calcination temperature and time on crystal structure, morphology and grain size of products were investigated. Ions of Ba and Ti were doped to modify the properties of BiFeO₃ ceramics for improving ferroelectric and ferromagnetic properties. It is found that compared to the products before doping, the products with Ba doping at an amount of 30% in mass fraction can have the saturation magnetization enhanced from 4.69 emu/g to 4.93 emu/g; while the products with Ti doping at 10% in mass fraction can have the remnant magnetization enhanced from 0.047 emu/g to 0.164 emu/g. The co-doped ceramic samples combine the effects of A-site and B-site doping and exhibit enhanced multiferroic properties.

The thermal dissipation performance of a battery pack was optimized by thermal simulation, aiming to enhance safety and service life of batteries. A thermal simulation model of the battery pack was established with ANSYS software, and temperature distribution was analyzed for the battery discharged at 1C rate. It is found that the simulation results deviate from actual measurements by less than 0.5 ℃, confirming the high accuracy of the model. Two optimized thermal dissemination schemes were proposed, including I-shaped heatsink and thermally conductive adhesive filling. Study shows that both schemes can effectively improve the thermal dissipation performance, leading to the maximum temperature of cells reduced by 6.0 ℃ and 5.9 ℃, respectively. The scheme of I-shaped heatsink can not only reduce cell temperatures but also significantly reduce temperature differences, resulting in better thermal uniformity.

Bagasse was calcined under an inert atmosphere to produce biochar, which was then mixed with metakaolin and taken to prepare sugarcane bagasse biochar/geopolymer composite microspheres (BGM) by using sodium silicate as an activator. The microstructure of BGM was characterized by XRD, FTIR, BET and XPS, and its adsorption performance for crystal violet (CV) and methylene blue (MB) was also investigated. Results show that the introduction of biochar can enhance the adsorption capacity of metakaolin-based geopolymer microspheres. The adsorption processes of BGM for both dyes follow the pseudo-second order kinetic model. BGM-20 can have theoretically maximum adsorption capacities of 138.031 mg/g for CV and 79.128 mg/g for MB, which can be well-described by the Langmuir isotherm model. Dynamic adsorption experiments revealed that the time required for adsorption of CV and MB by BGM to reach exhaustion exceeded 8 500 min, indicating that BGM can be taken as a fixed-bed adsorption medium material for dye wastewater treatment.

The immersion end quenching method, combined with hardness testing, metallographic microscopy, scanning electron microscopy and transmission electron microscopy, was used to investigate the effect of quenching rate on the age hardening of 6061 aluminum alloy for building formwork. Results show that when the quenching rate decreases from 305 ℃/s to 26 ℃/s, the post-aging hardness of the alloy remains nearly unchanged. However, when the quenching rate drops below 26 ℃/s, the hardness decreases rapidly with further reduction in quenching rate. At quenching rates below 26 ℃/s, solute atoms precipitate from the supersaturated solid solution during cooling, forming β (Mg₂Si) phases without strengthening effect at grain boundaries, Al₁₃ (Fe, Cr)₃Si₂ dispersoids, and dislocations. This reduces the number of β″precipitates in the grains after aging, thereby lowering the alloy hardness. Lower quenching rates result in more β phases and lower post-aging hardness. It is concluded that the quenching rate shall exceed 26 ℃/s for attaining high hardness alloy.

In order to study the high-temperature and high-pressure sintering of binderless tungsten carbide (WC), X-ray diffraction, scanning electron microscopy, universal testing machine, and microhardness tester among others were adopted to characterize the phase composition, microstructure and mechanical properties of the WC samples. The results show that the relative density, hardness and fracture toughness of the samples increase as the sintering temperature rises. It is found that WC sample prepared by sintering at 1 500 ℃ can exhibit excellent comprehensive mechanical properties, with relative density of 99.5%, hardness of 2 885HV, and fracture toughness of 9.50 MPa·m^1/2.

Extreme high-speed laser cladding (EHLA) technology was used to prepare Al₂O₃-316L coatings on Ti6Al4V rods. The effects of scanning speed, powder feeding rate on single-track coating quality, and 316L powder content on multi-track coating quality and corrosion resistance were explored. Results show that with the following optimum process parameters, including scanning speed of 250 mm/s and powder feeding rate of 8 g/min, the coating can present superior quality with the 316L powder in a mass fraction of 20%. It is shown that all Al₂O₃-316L coatings exhibit superior corrosion resistance compared to the substrate. As 316L content increases, the corrosion resistance of coatings increases followed by decline. With 316L powder in a mass faction of 20%, the electrochemical impedance of the coating is 2.27 times that of the substrate.

The relevant literature on laser-MIG hybrid welding of aluminum alloy from the China National Knowledge Infrastructure (CNKI) core journal database and Google Scholar database in 2000-2023 was systematically analyzed by using VOSviewer. Three primary research focuses were identified by analyzing citation frequencies of key literature and the evolution of research hotspots: ① the interaction between laser and MIG heat sources, particularly the effects of laser-arc distance and heat source leading modes on plasma behavior and molten pool stability; ② hybrid welded joints, revealing the formation mechanisms and optimization strategies for defects such as porosity and cracks by investigation into morphological characteristics; ③ mechanical properties of welded joints, focusing on microhardness distribution and softening mechanisms in the heat-affected zone. Results indicate that the transition of Mg and other alloying elements can be effectively achieved by adopting welding wire alloying, and after heat treatment of those heat-treatable aluminum alloys, the welded metal exhibit remarkably enhanced strength and hardness through aging. The subsequent researches can employ multi-scale numerical simulations to explore the dynamic coupling mechanisms between laser and arc, and the interaction between droplet transfer and keyhole stability, as well as to optimize process parameters to suppress porosity and overcome the technical bottleneck in simultaneously improving welding speed and quality. This review can provide insights for enhancing the performance of laser-MIG hybrid welding of aluminum alloy.

The effect of Cr content in mass fraction on the microstructure and mechanical properties of Al-Cu-Mg-Ag alloy with a low Cu/Mg ratio was investigated. Results indicate that after an addition of Cr to the Al-Cu-Mg-Ag alloy with low Cu/Mg ratio, phases of Al-Cr and Al_1.6TiCr_0.4 are generated in the alloy; with Cr content from 0.17% up to 0.22%, the alloy has its tensile strength improved from 463 MPa to 484 MPa (a 4.5% increase), and its yield strength enhanced from 288 MPa to 319 MPa (a 10.8% increase). The enhancement in mechanical properties is attributed to solid solution strengthening by Cr and precipitation strengthening by S′ phases.

To gain an in-depth understanding of research status of ceramic additive manufacturing, the technical processes of direct ink writing, fused deposition modeling, selective laser sintering, stereolithography and digital light processing, as well as the materials used in those technologies are reviewed based on domestic and international researches on ceramic additive manufacturing. The advantages and disadvantages of those five technologies are summarized, which can provide references for their application scenarios. Finally, the prospect for the development of ceramic additive manufacturing is also discussed.