Both preliminary heat treatment and final heat treatment play an irreplaceable role in the production of aluminum alloy products. The homogenization degree of compositions, the size of the dispersoid and its coherent relationship with the matrix, the size and aspect ratio of recrystallized grains, the supersaturation of solutes, and the characteristics of precipitates directly determine the mechanical properties, corrosion resistance, and the workability of materials. In engineering applications, non-isothermal phenomena involving heating and/or cooling processes are inevitable due to the impact of product scales. Therefore, novel heat treatment technology with higher engineering applicability is a necessary extension of the solid-state phase transformation theory. Based on the typical wrought aluminum alloys such as AlZnMg(Cu), AlMgSi, and AlCu(Li), the current researches on engineeringable homogenization, solid solution, and aging technologies were summarized. The novel technologies focused on multistage heat treatments and non-isothermal heat treatments.

Due to their poor plasticity and corrosion resistance, as well as their flammability in the air, magnesium alloys are limited in large-scale application. To address the above issues, magnesium alloys can be combined with aluminum alloys with superior plasticity and flame retardancy, resulting in high strength and good plasticity of composite laminates at room temperature, and lighter weight. Therefore, this article selects 5052 aluminum alloy as the outer layer of the laminated plate and AZ31 magnesium alloy as the inner layer material to study the effect of the precipitation of intermediate compounds at the interface of this laminated material under high-temperature creep conditions on the creep properties of the material. The results showed that the layer thickness of Al/Mg/Al laminate composite was about 50 mm. The main orientations of 5052Al alloy were (001) and (101) directions, while the main orientations of AZ31Mg alloy were (01

Binary metal-metal composites are promising for advanced applications. In general, the interface between adjacent metals may have a great influence on generation and propagation of fatigue cracks. However, limited research has been devoted to investigating the fatigue properties of laminated metal-metal composites. Here, we fabricated a laminated Ti-Ta metal-metal composite through powder metallurgy method, followed by hot deformation subsequently. The fatigue life and the fracture surfaces under different alternating stresses were investigated systematically. The results reveal that the fatigue strength of the Ti-Ta metal-metal composite is 450 MPa, significantly surpassing that of pure Ti. The Ta area presents the fatigue striation characteristics while the Ti area shows the cleavage fracture inside the fatigue stable propagation region. Besides, the interfaces between Ti and Ta areas could restrict the crack growth and/or change the direction of crack propagation. Owing to the direction of crack propagation changing constantly, the fatigue fracture surfaces present a “step-like” microstructure, which is first reported in laminated metal-metal composite. This work provides a novel model for fatigue crack propagation in laminated metal-metal composite.

TiNb alloys are widely used in the field of cryogenic superconductivity because of their excellent plasticity, machinability and superconductivity. As a common softening behavior in the process of material processing, dynamic recrystallization (DRX) has a considerable effect on the microstructure and the properties of material. The discontinuous dynamic recrystallization (DDRX) behavior of TiNb alloys during hot compression has been studied by combining experiment with cellular automaton (CA) simulation in this paper. It can be found that CA model can effectively predict DDRX behavior of TiNb alloy. The mean grain size and the volume fraction for DDRX of TiNb alloys increase with increasing deformation temperature, but they decrease with increasing strain rate. Furthermore, the serrated grain boundaries and the nucleation points of recrystallized grains in the deformed TiNb samples are in accordance with the characteristics of grain boundary bulging mechanism. In addition, the random orientation effect of DDRX grains is helpful to weaken the intensity of deformation texture in TiNb alloys.

In this work, a method for the formation of legs of n- and p-type thermoelements by screen printing using zinc phosphate cement and aqueous alkaline sodium silicate solution as binders was developed. Thermoelectric properties of thick films were investigated. A prototype of a flexible thermoelectric generator (TEG) was developed and fabricated using the results obtained by the screen printing method from suspensions based on Bi₂Te₃-Sb₂Te₃ (p-type) and Bi₂Te₃-Bi₂Se₃ (n-type) with an aqueous alkaline sodium silicate solution as binder. The developed prototype includes 6 pairs of n- and p-type legs connected by copper wires, and a silicone matrix was used as a flexible base. The prototype showed that at room temperature (298 K) the output voltages of the flexible thick film TEG at temperature differences ΔT=2.5 and 10.0 K are 0.8 and 14.8 mV, respectively.

Dense B₄C composites were fabricated by hot-press sintering using B₄C and nano-scale yttrium oxide as the raw materials. The effects of Y₂O₃ content and sintering temperature on the microstructure and mechanical properties of B₄C composites were studied. And the grain growth mechanism and the strengthening and toughening mechanism were discussed. B₄C-1 wt% Y₂O₃ composites (sintering temperature: 2000 °C, pressure: 30 MPa, dwell time: 1 min) have the best properties, with the relative density of 99.6%, bending strength of 588 MPa and fracture toughness of 5.0 MPa·m^1/2. Abnormal grain growth was found in B₄C-Y₂O₃ composites, including twins and coarse grains. The grain growth is affected by the complex interaction of yttrium oxide and the grain boundary of boron carbide. The toughening mechanism of B₄C composites follows self-toughening and twinning-toughening, and the transgranular fracture and intergranular fracture coexist.

Different vanadiferous titanomagnetites commonly show different sintering performance and the underlying reason is the difference in mineralization behavior. In this work, a mineralization mode for vanadiferous titanomagnetites sintering was developed and mineralization behavior for vanadiferous titanomagnetites was compared by thermodynamic analyses. Besides, the sintering performance was clarified by substitution for each other. The results indicate that sintering performance shows an excellent correlation with mineralization behavior in the novel mineralization mode. The difference in mineralization behavior and sintering performance of vanadiferous titanomagnetites was attributed to the discrepancies in TiO₂ and SiO₂ content, and a higher SiO₂ content was able to offset the negative impact of TiO₂ at a fixed basicity. As the TiO₂ content in titanomagnetite increased from 1.53% to 4.30% with a similar SiO₂ content, the liquid phase amount, mechanical strength, calcium ferrite in the liquid phase, and reduction disintegration performance of sinter decreased significantly. However, when ilmenite with TiO₂ and SiO₂ contents of 7.99% and 3.86% was used to replace ilmenite with TiO₂ and SiO₂ contents of 4.30% and 2.12%, the reduction disintegration index decreased by less than 4%. The strength of sinter increased by 1.60%, and the yield increased by 2.56%.

The floor of inclined coal seams during mining is prone to seepage instability, resulting in water loss and even water inrush. The production of inclined coal seams occupies a certain proportion in China. Therefore, it is necessary to carry out the research on the floor structure stability in response to underground mining. Firstly, a four-side solid support inclined laminate model was established by analyzing the stress state and deformation failure law of inclined floor under the action of bidirectional linear load. Then, by studying the relationship between permeability coefficient and deformation, the method and conditions for determining seepage stability are obtained, and the influencing factors and sensitivity of water protection mining in inclined coal seams are determined through engineering cases. The inclined floor deflection curve is not symmetrical; the maximum deflection of the inclined coal seam floor is located at a distance of 0.5864 times the length of the working face in the middle and lower part of the working face, and at a distance of 0.5864 times the advance distance of the working face in the advancing direction. Through an orthogonal experimental analysis, the significance order of the factors affecting the deflection of the bottom plate is as follows: working face length > water pressure > advance distance > dip angle. The boundary of the upper layer in the laminated plate is a compressive stress area, while the middle layer is a tensile stress area. The opposite is true for the middle and lower layers, where shear stress is concentrated in different regions. The maximum stress values in the lower area of the working face are greater than those in the upper area, showing an obvious asymmetry. Finally, the evaluation indicators and stability conditions for seepage stability were determined: the ratio of the ultimate permeability coefficient (K_li) to the equivalent permeability coefficient (K_eq) should not be less than 1, that is, K_li/K_eq≥1. The significance of the factors affecting seepage stability is as follows: water pressure>working face length>dip angle, which can provide guidance for water protection mining in similar mines.

Gob-side entry retaining (GER) is a technique in non-pillar mining, which maintains the original mining roadway along the edge of gob and retains it as a mining roadway for the subsequent working face. This technique offers significant advantages such as a high coal mining rate and cost-effective roadway retention. This paper focus on the GER implementation in 52605 panel of Daliuta Coal Mine and introduce an innovative technique involving the utilization of flexible formwork concrete wall (FFCW). To verify the feasibility of this technique, a numerical model was established. Furthermore, the stability mechanism of surrounding rock during the mining process of 52605 panel was thoroughly examined. Simulation results indicate that during the mining, the roadside backfill body (RBB) gradually bears load, causing peak stress transfer from gob side towards solid coal side. Moreover, plastic zone of roof and solid coal exhibited a noticeable increase, leading to a combined tensile-shear failure. Based on the stress and plastic zone evolution characteristics of surrounding rock during the mining process of the working face, control techniques were proposed and industrial experiment was successfully carried out. Ultimately, on-site monitoring results show that the deformation control effect of surrounding rock was good, and there was no obvious pressure manifestation in the working face.

The lime method is one of the most common flotation processes, which can achieve flotation separation of scheelite, fluorite and calcite. The large amount of calcium ions released by lime easily formed calcium dioleate colloids with fatty acid anions, which was overlooked in the classical action mechanism of the lime method. The solution chemistry calculations revealed that calcium dioleate colloid was the main action component in the pulp of lime method. The fluorite surface was covered by calcium carbonate as a result of increased surface transformation reactions, and the surface properties were similar to calcite surface. The size of calcium dioleate colloid in lime method slurry was 100–600 nm, and the amount of lime significantly affected its size and size distribution. Selective adsorption of calcium dioleate colloids occurred on the surface of scheelite, and its adsorption effect on the surface of fluorite was weakened due to surface transformation. The excellent selectivity of the lime method was explained by the selective adsorption of calcium dioleate on the surface of scheelite, which was further enhanced by the surface conversion reaction of fluorite to calcite. The new mechanism completes the classical theory by complementing the role of calcium dioleate in lime flotation.

Aluminum nitride (AlN) in aluminum dross could be hydrolyzed in humid air, releasing a large amount of NH₃. NH₃ can harm environment and human health when exposed to air, but it could be recycled and utilized after effective disposal. This paper studied the effects of reaction temperature, liquid-solid ratio, and time on hydrolysis behavior, and optimized experimental conditions using response surface methodology, in response to characteristics of long reaction time and incomplete reaction in AlN hydrolysis. Hydrolysis rate of AlN was 92.45% under the optimum experimental conditions of: reaction temperature of 95 °C, reaction time of 11.2 h, liquid-solid ratio of 7.8: 1 mL/g, and stirring speed of 400 r/min. Reaction kinetics studies showed that hydrolysis process was controlled by a surface chemical reaction control model with an apparent activation energy of 40.24 kJ/mol. XRD and SEM-EDS results showed that AlN transforms into Al(OH)₃ adhering to the surface of aluminum dross, with the crystals growing over temperature and time. This work provided value for recycling of NH₃ from aluminum dross.

In this study, firstly, an ultra-pure magnetite concentrate with 72.12% Fe and 0.09% Si was obtained by reverse flotation from superior magnetite concentrate with 68.38% Fe and 2.33% Si. Then, using the ultra-pure magnetite concentrate as raw material, high-purity reduced iron powder with Fe grade of 99.06% was prepared by Höganäs process, of which bulk density, mobility and compressibility were 2.34 g/cm³, 9.01 s/(50 g) and 6.55 g/cm³, respectively. The high-purity reduced iron powder reached the MHF80·235 (superior) grade in the enterprise standard of iron powder for powder metallurgy (MHF/QB-2016). We used it to prepare lithium iron phosphate with first charge capacity of 168.20 mA·h/g by coprecipitation method. Compared with iron scale, the ultra-pure magnetite concentrate did not require a magnetic separation in Höganäs process, and needed a shorter coal-based and hydrogen reduction time. Besides, its reduced iron powder had a higher Fe grade and better process performance. Mechanisms for improvement of the process performance of reduced iron powder were proposed: an increase in the coarse particles percentage and Fe grade of reduced iron powder could significantly improve its bulk density and compressibility, and an increase in the coarse particles percentage also could improve its mobility.

Understanding the role of surface roughness in flotation is crucial to obtain the highest technical and economical efficiencies of flotation operations. In this review, the fundamentals of the static wetting and the dynamic attachment/detachment of bubbles on rough surfaces are discussed with special focus on the comparisons with the mechanisms in the case of ideal surfaces. The gaps between current research in dynamics of bubble-particle interaction in ideal cases and the real mineral particles in flotation are identified. In addition, the impacts of surface roughness on real mineral flotation are clearly discussed by combining collector, nanobubbles and wetting state. The fundamental mechanisms in ideal case may not be applicable, or only partially applicable to the real mineral flotation operations. The future research directions on enhancing the role of surface roughness in flotation separation recovery of real mineral particles were proposed, such as developing suitable techniques to quantify surface roughness of real mineral solids, and correlating the dynamics of bubble-particle interactions in ideal case with the real mineral particles.

As a typical iron-containing silicate, it is challenging to separate chlorite from specularite owing to their similar density, magnetic and surface physicochemical characteristics. Gum arabic (GA) was used as selective depressant for the separation of specularite from chlorite using dodecylamine (DDA) as the collector to resolve this issue. Moreover, the depressing mechanism of GA was investigated using flotation experiments, adsorption amounts measurement, Zeta potential detection, contact angle measurement, Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The single-mineral flotation results indicated that the recovery of specularite and chlorite reached 22.1% and 82.4%, respectively, with 90 mg/L GA and 20 mg/L DDA at pH=8. Furthermore, artificial mixed ore flotation test verified the selective depressing effect of GA on specularite. Surface adsorption, contact angle, and Zeta potential studies all indicated that GA has a more affinity for adhering to the surface of specularite than chlorite, and that pro-adsorbed GA inhibits the following adsorption of DDA, which reduces specularite’s capacity to float. The FT-IR and XPS analysis results demonstrated that GA adsorbs on the surface of specularite mainly via chemisorption, and the hydroxyl groups of GA interact with iron sites on the mineral surface to form metal chelates.

Red mud is a highly alkaline solid waste with very fine particles produced in the production of alumina from bauxite, which is difficult to utilize comprehensively. In this paper, microbial mineralization is applied to the treatment of sintering red mud, and the mineralized products with good cementation characteristics generated in the reaction process are used to cement and solidify the red mud, so as to realize the purpose of using red mud to produce building materials and foundation filling materials. The test shows that mineralizing bacteria can overcome the characteristics of strong alkalinity, high salinity, and fine and uniform particles of red mud, the unconfined compressive strength (UCS) of the red mud sample can reach about 3 MPa and the maximum amount of the newly formed carbonate is 27%. Moreover, due to the unique microstructure characteristics of red mud, it is difficult for mineralizing bacteria to adhere to the surface of red mud particles and their aggregates, thus they are suspended in pores. Therefore, most of the formed calcium carbonate crystals form aggregates, showing a stacking state. Based on this, a new microbial mineralization and cementation mechanism is established, which is suitable for fine particulate matter.

The whale optimization algorithm (WOA) is one of the meta-heuristic algorithms that achieve parameters optimization by simulating the feeding behavior of humpback whales. The WOA can be applied to self-potential (SP) data inversion for regular polarized geometric objects (i.e., sphere, horizontal cylinder, and vertical cylinder), which can assist in exploring subsurface geological objects. The WOA was first applied to perform parameter inversion on three models: the sphere, the vertical cylinder, and the combination of both models. The optimization process of the vertical cylinder model parameters was analyzed, and the convergence behavior of the WOA was discussed. Secondly, laboratory-measured data from three sets of physical models were used for parameters inversion, and a comparison was made with two other optimization algorithms to demonstrate the advantages of the WOA. Finally, the WOA was applied to process a set of field data. The WOA algorithm was employed for the inversion of SP data inversion from numerical experiments, physical experiments, and field examples. The inversion results demonstrate that the proposed WOA inversion has good stability and effectiveness in solving the self-potential inversion problem.

In this paper, the flow characteristics of an air chamber inside a tunnel when subjected to train-nose-entry wavefronts were analyzed using numerical simulation. The results demonstrate that there exists a specific range of connection sizes for a fixed volume of air chamber, which imparts an under-damped characteristic to the chamber. Additionally, the pressure distribution within the air chamber and tunnel exhibits a noticeable three-dimensional effect as a consequence of the non-uniform flow field at the connection of the air chamber. The difference in the numerical results of the maximum pressure gradient is primarily observed at the air chamber connection when comparing the axisymmetric model to the one-dimensional model. However, this difference gradually diminishes to approximately 1% after the wavefronts have traversed through the air chamber for a distance of approximately 5 m. Furthermore, a scaled experimental setup was constructed to compare the obtained numerical results with the experimental data, successfully validating the accuracy of the numerical method.

With the vigorous construction of intercity railways, the environmental vibrations along the railways, especially in buildings with precision instruments (PI), have been deteriorating, and the internal instruments are affected by repeated vibrations. The train-induced vibrations will be more severe when two trains meet at a high speed. In this study, numerical simulation analysis of PI in adjacent buildings was carried out. A coupling model of high-speed trains meeting was developed, and a method for predicting vibration superposition was proposed. The existing vibration data were collected and used for model verification. Based on this, the vibrations of PI were evaluated, and corresponding measures were proposed. The prediction results show that the dominant frequency of the existing vibrations is 10–20 Hz, and there is a risk of excessive vibrations in this frequency range. PI can be affected by high-speed trains meeting, resulting in abnormal operation. The high-frequency train-induced vibrations (40–80 Hz) are effectively alleviated by the damping pad. After the superposition of train-induced vibrations and existing vibrations, the vibrations on higher floors are mainly in the 10–20 Hz range, which requires attention and implementation of reduction measures for PI.

In order to improve the accuracy and efficiency of the train-track-bridge coupled system (TTBS) dynamics random analysis under the excitation of track irregularities, a full information representation of the track irregularities is required while minimizing the number of track irregularities. To realize full information representation and simulate random track irregularities with a small number of samples, this paper proposes a combined method of the adaptive sampling method (ASM) and the modified stochastic harmonic function method (MSHF). The ASM can reduce the number of samples by selecting highly representative points that match the spectral probability distribution from the aforementioned set. The obtained point set is substituted into the independent variable added in the stochastic harmonic function (SHF) in order to achieve accurate simulation of the track irregularity time domain samples. Compared with the traditional method, the proposed method can achieve highly accurate simulation of track irregularities with small samples. By considering the TTBS dynamic analysis as an example, the combined method can improve precision while reducing computation time by 41.67% of random analysis.

A deformation of an existing tunnel is complicated when a shield tunnel undercrossing and vertical paralleling excavates with existing tunnel in composite stratum. Therefore, a novel deformation calculation method is proposed for the existing tunnel considering slurry consolidation and shield undercrossing and vertical paralleling excavation. First, the equivalent layer method is used to simplify the composite stratum, the deformation caused by different factors is analyzed, and the slurry consolidation equation is introduced to correct it. Then, according to the subsection calculation idea, the calculation formula of shield undercrossing and vertical paralleling with the existing tunnel is established. Finally, considering an actual engineering case, a finite element model is established to analyze the deformation of the existing tunnel. Results show that before the shield construction section overlaps with the existing tunnel, the deformation curve of the existing tunnel generally exhibits an “M” form; After the overlap, the deformation curve of the existing tunnel gradually becomes “U” shape, and the maximum deformation point moves from the overlapping point to the shield tunneling direction; The settlement deformation range of the existing line gradually expands, and the maximum deformation increment gradually decreases and tends to stabilize.

Wetting-drying cycles of weathering loading frequently lead to failure of infrastructures in loess regions, China. Water retention behaviours of loess are key information for capturing the physical causes of loess engineering problems. To demonstrate variations in water retention performance of intact and recompacted loess from three regions due to a purely environmentally driven deterioration process, laboratory testing programmes were carried out to measure soil water retention curve (SWRC) and microstructure, by incorporating employing a pressure plate apparatus and scanning electron microscope. According to the laboratory results, the wetting-drying weathering has a significant impact on the water retention properties of intact and recompacted loess, especially after the first wetting-drying cycle. A distinctive feature was that the SWRC of the intact loess was bimodal, whereas that of the recompacted loess was unimodal. The features of water retention behaviour and its variations as well as linking with soil microstructure were well interpreted by the conceptual model, considering multiple influences including wetting-drying cycles, soil fabric and regional variability. A new equation was proposed to provide a unified description about the water retentions of both intact loess with bimodal behaviour and recompacted loess with unimodal characteristics. The parameters were able to define the variables of SWRC, and it was highly usefulness and effectiveness in terms of external environmental influences, such as multiple wetting-drying cycles, soil fabric, regional differences and soil types.

Sandstone is commonly found in mountainous regions of China, and the mountain tunnels are often built in sandstone strata. The tunnel surrounding rocks often suffer from elevated temperature and acidic solutions during tunnel construction and operation. In this study, the energy evolution and failure characteristics of sandstones under elevated temperature and acidic solutions were investigated by observing the compressive strength, elastic deformation energy density, dissipative energy density, failure mode, and fracture distribution characteristics of sandstone through uniaxial compression tests and computed tomography scanning. The findings indicate that elevated temperature and acidic solutions had a significant impact on the energy distribution and failure mode of sandstone, and their effects on the failure mode and fracture distribution characteristics of sandstone varied at different stages. The influence of elevated temperature on the energy distribution and failure mode of sandstone was more pronounced compared to that of the acidic solution. Furthermore, the elastic deformation energy density and dissipative energy density of sandstone showed a close linear relationship with failure characteristics. These conclusions could provide a theoretical significance for the design and construction of rock structures under complex high-temperature conditions, and associated tunnel projects.