Aiming at complicated flow field of Y-shaped pipe in pump piping system and risk of ore leakage in conveying test for deep sea mining, numerical simulation was performed by using CFD-DEM method for ore particles with different velocities, different volume concentration and different particle sizes. Based on that, the movement features of particle groups and flow field distribution pattern in Y-shaped pipe were all analyzed. It is found that the flow field distribution in Y-shaped pipe is influenced by the curvature of pipe elbow and the flow distribution in the inlet of Y-shaped pipe. The particle groups flow against the inner wall of elbow, and deflect upward under the influence of upward flow. If upward flow with lower velocity, particles with large grain size and high volume concentration will hit the bottom of pipe, leading to some losses. As the upward velocity decreases and both particle volume concentration and grain size increase, more and more particles will be continuously lost on the bottom of pipe. Due to the existence of particle flow, both intensity and scale of the low-pressure vortex region in Y-shaped pipe become weaken.

As for pipes with different lengths, with heave compensation device replaced by elastic constraint, a vibration equation was established by using energy integration approach, and the dynamic response of lifting pump installed at different positions of pipes was analyzed by finite element method. Results show that the harmonic response of stress excited by the following single loads was in an ascending order: torque, wave in longitudinal direction, and a combination of wave and current in horizontal direction. Under excitation by all these three loads with the same phase, the harmonic response of the system increased significantly. When the installed lifting pump was changed from a high position to a low position, the maximum equivalent stress of pipeline increased after an initial falling down. The installation position of lifting pump on the pipe corresponding to the minimum of the maximum equivalent stress was the suboptimal installation position. Based on the suboptimal installation position for the lifting pump on the pipeline with specific length, an empirical formula was established for the suboptimal installation position, which can provide reference for the quantitative design of lifting system.

It is difficult to simulate and analyze distribution of seepage field for the slope at the entrance of excavated tunnel during heavy rainfall. Aiming this problem, a slope project at a tunnel entrance was taken for study, and FISH language in the FLAC^3D was redeveloped to determine the permeability coefficient of soil under different saturation state during rainfall infiltration, and the boundary conditions for rainfall infiltration were updated in real time. In addition, the pore water pressure, matrix suction distribution, as well as safety and stability of the slope at the tunnel entrance after different support schemes were all analyzed with different rainfall durations. The results showed that after 24 hours of heavy rainfall, the slope before and after a combined support including anti-slide piles and anchor cables all reached saturation state, that is, the saturation line ran through from the foot to the crest of the slope, while the slope, after benching and being supported with bolt, had its surface soil from the foot to the secondary platform of the slope under a saturated state. As for the slope at tunnel entrance supported by anti-slide pile combined with anchor cable, the variation law of its safety factor during rainfall was consistent with that of the slope without support treatment, showing that the factor of safety tended to be stable after an initial rapid decrease, and gradually reached 1.2. As for the slope after benching and being support with bolt, its factor of safety decreased a little and maintained above 1.8. It is concluded that the factor of safety, excavated earthwork quantity and total investment for the support scheme should be taken into consideration before starting a slope engineering at a tunnel entrance, and a combined support scheme including anti-slide pile and anchor cable is superior to the scheme including benching and support with bolt.

By using CFD-DEM coupling approach and Archard wear model, a slurry pump with small flow was numerically simulated under the conditions including different flow rates and particle sizes. Based on the analysis of the movement law of particles in the pump, the distribution of particles in different regions of pump and the collision between particles and wetted parts of the pump, the wear characteristics of wetted parts in the slurry pump, especially the volute were studied. The results show that there is some blockage in the volute approaching the tongue region due to a slow flow rate of particles. It is found that wear of the volute is mainly concentrated on the upper part and near the tongue region. With the increase in the flow rate and velocity of particles, the kinetic energy of the particles collide with the pump wall increases, resulting in serious wear on the body of slurry pump. And the wear will become more serious by the particles with small grain size.

Some typical rock was taken as the sample in an experiment to study the mechanical properties of white sandstone under uniaxial compression with strain rates ranging from 10^-5 s^-1 to 10^-3 s^-1. The surface displacement contours of the samples were observed and collected by using 3D-DIC system, and the difference in the deformation and failure characteristics of samples under the effect of different strain rate was also analyzed. The results show that the variation of displacement field on the surface of rock sample reflects an evolution law of failure surface, and there is a corresponding relationship between shear failure plane and concentrated displacement field. The difference in the overall axial strain mainly occurs during the period from micro-crack compaction to elastic deformation. At an initial stage of loading, there is difference in the overall radial strain. The lower end part of the sample has the largest radial displacement when the strength reaches the peak, while the upper end part is deformed under the impact of the end effect. The radial outward expansion is limited by the friction between the end face and the gasket. In addition, the local axial strain at the lower end is greater than that at the upper end. With an increase in the loading rate, rock sample has its mechanical characteristics converted from ductility to fragility. During the failure process of rock sample under the uniaxial compression with a lower loading rate, the occurred pore collapse results in friction effect due to the closure again and slippage of some cracks, thus there appears fluctuation in the stress-strain curve near the peak strength. It is shown that the mechanical parameters (peak strength, elastic modulus and Poisson's ratio) of white sandstone increase as the loading rate increases.

A concept of short delay blasting with blastholes in a combined fan pattern was put forward, in which a row of reinforced holes were added between each row of conventional fan-pattern holes, and detonation was initiated with short delay interval between the conventional row of holes and the added row of holes. The blasting scheme with different delay interval, and blastholes loaded with different confining pressure were numerically simulated with ANSYS/LS-DYNA. It is found that blasting crater cannot be effectively produced by adopting the scheme with conventional holes in fan pattern under high geo-stress environment, while the scheme of short delay blasting with holes in combined fan pattern is more effective in obtaining damaged and ruptured rock, showing better rock breakage effect. In addition, analysis of crack propagation under different confining pressure shows that the blasting crack tends to grow in the direction of the maximum principal stress. The numerical simulation and field engineering practice have proven that when there is an acute angle between the maximum principal stress and that added row of blastholes in fan pattern, that is, higher confining pressure is loaded in the direction of the horizontal row of holes, and lower confining pressure is loaded in the direction of the vertical row of holes, the short-delay blasting with blastholes in such a combined fan pattern can not only improve the rock breakage effect, but also effectively keep rear row of blastholes and the rock mass behind not impacted by the blasting.

The impact of blasting vibration on the open-pit slope in a limestone mine was explored. The characteristics and law of blasting vibration was investigated by performing field blasting vibration tests based on the consideration of geological conditions on site. Based on fitting with Sadowski formula, an obvious attenuation trend was found for the velocity of particle vibration in the data about two field blasting vibration. With Sadowski formula modified based on elevation effect, the correlation coefficient was up to 0.94, better than the fitting effect by the traditional Sadowski formula. The maximum vibration velocity on each bench of limestone slope was predicted by using the modified fitting formula in this paper, and considering the designed detonate charge for steep end-slope, showing that the impact of vibration source on the adjacent bench should be taken into consideration in blast design.

Qingdao Metro Line 8 was taken as an example for studying the surrounding rock stability of underground tunnel in mud-containing sandstone stratum with pore water. Based on the analysis of deformation and stress evolution law of surrounding rock by simulating three different pore water conditions, the maximum values of vertical displacement (roof subsidence), horizontal displacement (side walls moving closer), vertical stress, horizontal stress and shear stress of the tunnel were finally obtained. The numerical simulation results of tunnel with three kinds of pore water content were applied to the tunnel construction for Qingdao Metro Line 8, and the on-site monitoring results show the deformation of surrounding rock of tunnel roof and side wall is all controlled within the safety range. It is shown that such numerical simulation results provide good reference for the construction of Qingdao Metro Line 8.

A kind of similar rock material was prepared with gypsum and quartz sand, and influence of seven factors on the strength index of the material was analyzed by performing laboratory tests. The results show that curing temperature and material density are in positive correlation with material strength index, while curing humidity, sand-to-binder ratio, ash-to-paste ratio, fine-grained quartz sand content, as well as water content are in negative correlation with material strength index. Based on the calculation of the sensitivity indices of different influencing factors, it is found that material strength has a sensitivity of only 4.5% to curing temperature, a sensitivity of 104.9% to sand-binder ratio. Factors of curing temperature, water content, material density, curing humidity, ash-to-paste ratio, fine-grained quartz sand content and sand-to-binder ratio are in an ascending order in terms of their sensitivity to uniaxial compressive strength; while factors of sand-to-binder ratio, ash-to-paste ratio, material density, curing humidity, water content, fine-grained quartz sand content and curing temperature are in a descending order in terms of their sensitivity to tensile strength.

An experiment on flotation of calcite in pulp with pH of 8.0 and the dosages for sodium silicate and sodium oleate respectively at 300 mg/L and 1.5 × 10^-4 mol/L was performed by using ultrasonic wave with the frequency at 40 kHz, for investigating the influence of ultrasonic power and sonication duration on the flotation behavior. The variation of sodium oleate content on the surface of calcite was analyzed by adsorption measurement, the chemical status of elements on the calcite surface was analyzed by XPS, and the variation of adsorbed reagents was also analyzed by zeta potential measurement. After 15 min-ultrasonication (40 kHz, 150 W), the flotation recovery of calcite can be increased from 8.5% to 82.7%. It is found that ultrasonication can bring in an increase in the adsorbed amount of sodium oleate on calcite, a decrease in the intensity of Si2p on calcite, and also an increase in the content of C1s. Meanwhile, the deconvolution of O1s spectrum shows reduction in the peak area of sodium silicate, but an increase in that of sodium oleate, and the surface zeta potential of calcite almost unchanged. The results indicate that the ultrasonication can induce a desorption of sodium silicate from the depressed calcite in the pulp containing both sodium silicate and sodium oleate, thus the freshly vacancy can be adsorbed by sodium oleate, leading to the significant improvement in floatability of calcite.

A medium-low grade calcium-magnesium phosphate ore was ground to a fineness of 56.74% -0.075 mm and was used to study the liberation characteristics of particle size within varied ranges on its flotation behavior. The particles were classified into coarse ranges (+0.15 mm, -0.15+0.106 mm and -0.106+0.075 mm) and fine ranges (-0.075+0.038 mm and -0.038 mm). The content of different minerals in each size range was estimated by using X-ray fluorescence spectroscopy and X-ray powder diffraction analysis, while the intergrowth and monomer liberation was evaluated with the backscattering images obtained from scanning electron microscopy. It is found that the content of liberated minerals increases as the particle size decreases. Fluorapatite is primarily enriched in the coarser particles within the size range of +0.075 mm, whereas dolomite is concentrated mainly in fine particles of -0.075 mm. By improving the selective aggregation of valuable minerals and gangues in size range of -0.038 mm, the P₂O₅ loss can be reduced. Furthermore, by reducing the content of coarse particles within the size of +0.075 mm and increasing the content of particles within -0.075+0.038 mm range, both P₂O₅ grade and recovery of the concentrates can be effectively improved.

In processing a mud-bearing high-silver lead-zinc sulfide ore, collectors of dimethylphenyl dithiophosphate and aniline aerofloat were used in combination to collect lead minerals in a low alkali environment, while the noble metal of silver was comprehensively recovered. Furthermore, lime combined with 8372CN were used to depress pyrite in zinc flotation process, thus alleviating the influence of sludge on the quality of zinc concentrate. The closed-circuit flotation test yielded a lead concentrate grading 67.18% Pb at 94.57% recovery, 2 560.37 g/t Ag at 80.54% recovery and 3.60% Zn, and a zinc concentrate grading 51.63% Zn at 93.27% recovery. With this flowsheet, an efficient comprehensive utilization of a mud-bearing high-silver lead-zinc sulfide ore can be actualized.

A process consisting of pre-discarding with heavy medium separation and ambient-temperature flotation was adopted for a scheelite ore sampled from the middle-layer mining zone of a tungsten mine in Hunan Province. A heavy medium separation test with the ore size of -15+0.5 mm as the feeding show that in the heavy medium with the density of 2.37 g/cm³, 31.37% of yielded tailings can be discarded, while the obtained heavy product has WO₃ grade and recovery increased to 0.34% and 96.62% respectively. A test by using a process of desulfurization flotation plus ambient temperature flotation for scheelite demonstrates that the process of pre-discarding with heavy medium has little effect on the operation loss rate of WO₃ in sulfur-containing products. However, the raw ore is directly taken into the flotation without a pre-discarding will lead to more tungsten minerals left in the middlings. The closed-circuit test shows that after a pre-discarding by heavy medium separation, the tungsten concentrate from ambient-temperature flotation has its WO₃ grade and recovery reaching 5.50% and 84.15% respectively. It is concluded that pre-discarding by using heavy medium cyclone is conducive to improvement of tungsten product index and comprehensive utilization of tailings.

A mineral liberation analysis (MLA) automatic measurement technology was used to not only analyze the composition and dissemination of minerals in a skarn copper ore, but also investigate the characteristics like particle size distribution and mineral liberation degree of raw ore and bulk concentrate samples ground to different fineness. After a preliminarily study on beneficiation technique for such ore based on the obtained results, a processing flowsheet comprised sequentially of grinding, Cu-Pb bulk flotation, regrinding of roughing concentrate and Cu/Pb flotation separation. It is shown that such flowsheet with the primary grinding fineness of -74 μm 70% and the regrinding fineness of -20 μm 75% can produce a copper concentrate grading 20.88% Cu at 70.42% recovery, and 183.9 g/t Ag at 76.78% recovery, as well as a product of sulfur concentrate grading 32.65% S at 91.47% recovery.

Rhodococcus opacus (R opacus) was taken as a microbe collector in a flotation experiment to investigate the recoveries of cassiterite, calcite and quartz pure minerals. The results show that, with pulp pH as 4 and R opacus dosage as 1.24 g/L, the recoveries of these three minerals were correspondingly 82.07%, 45.42% and 13.66%. The interaction mechanism between R opacus and cassiterite was investigated by measuring zeta potential and surface tension. Finally, an open-circuit flotation experiment of tin ore was carried out with R opacus as the collector and sodium silicate as the depressant, showing that the grade of tin concentrate was improved from 3.98% to 23.83%.

A study on the separation of a copper-lead-zinc sulfide ore from Yunnan was presented by adopting a Cu-Pb-Zn full selective flotation process. The mineral liberation degree was enhanced by adopting fine grinding of raw ore and selective regrinding of lead roughing concentrate. A combined usage of depressants sodium sulfite and zinc sulfate benefited the synergistic effect and selectivity in depressing, and collectors Z-200, ethionitrogen and BK906 exhibited high selectivity. Under optimized parameters, a copper concentrate with Cu grade of 22.78%, Cu recovery of 83.28%, Pb content of 3.01% and Zn content of 4.23%, a lead concentrate with Pb grade of 75.86%, Pb recovery of 82.75%, Cu content of 0.17% and Zn content of 1.64%, and a zinc concentrate with Zn grade of 51.87%, Zn recovery of 93.16%, Cu content of 0.24% and Pb content of 0.31%, were obtained.

An experimental study was carried out for sulfur reduction and upgrading of a high-sulfur antimony-gold bulk concentrate from Russia with Sb grade of 24.58%, Au content of 76.92 g/t and S content of 14.46%. A closed-circuit flotation test was conducted using a new collector CJ-201 and a new depressant CJ-5S. The Sb and Au grades in the antimony concentrate attained respectively 42.26% and 92.36 g/t, with the corresponding recoveries of 88.04% and 62.18%. With this approach, a antimony-gold concentrate product with high content of antimony and low content of sulfur can be separated out from antimony-gold bulk concentrates collected in a Russian mine.

In order to comprehensively recover fluorite resources from the tailings left after hot flotation of scheelite, a beneficiation process consisting of regrinding, water displacement and concentration, and fluorite flotation was proposed. It is shown that with the feed ore with CaF₂ grade of 25.47%, a fluorite concentrate can be obtained with CaF₂ grade and recovery at 92.35% and 60.59% respectively.

Experiments were performed in a tube furnace for reduction roasting of high-iron manganese oxide ore, respectively with gas-based (CO) and pulverized coal as reducing agents. The effects of roasting temperature and roasting time on the simultaneous reduction of manganese and iron oxides therein were investigated. The results show that during the gas-based reduction roasting, the reduction process of Mn₂O₃ is controlled by chemical reaction, with apparent activation energy of 42.64 kJ/mol. However, the magnetization process of Fe₂O₃ is controlled by internal diffusion, with apparent activation energy of 21.30 kJ/mol. Compared to coal-based roasting process, Mn₂O₃ and Fe₂O₃ are easier to be reduced during the process of gas-based reduction roasting, and the manganese oxides can be directly reduced from Mn₂O₃ to MnO without the step of being reduced to intermediate product Mn₃O₄.

The influence of roasting on mineral decomposition under stable magnetic field was investigated. A direct reduction roasting experiment without carbon presence was performed for Bayan Obo lean iron, with roasting temperature of 950 ℃ and magnetic induction density of 1.02 T. Based on the analysis of the loss rate of mineral weight, mineral phase transformation and micro-morphology change by means of TG-DSC, XRD and SEM-EDS, the phase evolution law for rare earth minerals, gangue minerals and iron minerals under magnetic field was revealed. The results show that the decomposition time of bastnaesite is shortened by about 20 min after applying a stable magnetic field, and even the monazite with extremely low decomposition rate is almost completely decomposed after 60 min-roasting process. It is found that magnetic field can promote the decomposition and transformation of gangue minerals that cannot be decomposed without application of magnetism, and also accelerate the migration of alkali metal ions and the replacement of Fe²⁺ with fayalite.

The phase composition and morphology of a molten mixture of steel slag and furnace slag prepared at a high temperature was analyzed by X-ray diffraction and SEM-EDS scanning electron microscope to investigate the effect of MgO doping. The results show that MgO doping can effectively inhibit the formation of MgFe₂O₄ phase and non-gel Ca₂Al₂SiO₇ phase, and promote the formation of MgFeAlO₄ phase, thus increasing the melting point of the mixed slag. It is found that the mixed slag after doping 2% MgO presents a layered structure on its cross section. The inner layer has an increased proportion of MgFeAlO₄ phase, with uniform and fine pores; and the MgFeAlO₄ phase is wrapped by MgFe₂O₄ spinel with layered structure in the middle part; and the outer layer has Ca₂Al₂SiO₇ phase with uniform pores and moderate density. The mixed slag with such kind of structure is suitable to be used as the filter material for removing heavy metal ions.

With Bayan Obo niobium concentrate and semi-coke powder as raw materials, effect of basicity on melting process of the reduction product of carbon-containing pellets was observed in situ by using a high temperature heat table. The samples with optimum basicity were quenched and prepared at different melting conditions. The migration rule of elements during the melting process was analyzed by SEM-EDS, and the reaction rates of Nb and Si in the melting process were quantitatively analyzed by XRD, TG-DSC and ICP. Results show that with the binary basicity of 1.0, the spattering of molten slag can be effectively suppressed and the melting efficiency can be improved. With the basicity of 1.0 and temperature of 1 350 ℃, the SiO₂ in the slag is reduced at slag-gold interface and pulled into iron phase. After the molten slag is held at 1 400 ℃ for 2 min, the C in molten iron at slag-gold interface is preferentially reacted with the niobium oxide in the slag and reduced to NbC. A small amount of NbC is dissolved into the iron phase, and most of the remaining NbC is wrapped around the granular iron, forming a retention zone, which hinders the mass transfer at the slag-gold interface and reduces the reduction rate. After hot-holding at 1 400 ℃ for 10 min, the reaction rates of Nb and Si are 36% and 1.7% respectively. Titanium and rare earth are not involved in the reaction during the whole melting separation process.

In order to improve the efficiency of lithium extraction by brine adsorption, a process consisting of pre-concentration and adsorption was developed for lithium extraction. Based on the theory of phase diagram of Na⁺, K⁺//Cl^--H₂O ternary system at 50 ℃ and 100 ℃, variation of lithium concentration and lithium loss rate in brine at different temperatures with different evaporation rate was explored in the test, and the adsorption effects of adsorbents on brine before and after pre-concentration were compared. The results show that the concentration and loss rate of lithium in the solution are not affected by evaporation temperature. As the evaporation rate exceeded 40%, the loss rate of lithium in brine increased rapidly. The pre-concentrated brine with concentration of 55 mg/L lithium at an evaporation rate of 40% was adsorbed with manganese absorbent, showing that the lithium adsorption capacity reached 4.25 mg/g after 4 hours, higher than the adsorption capacity of 3.39 mg/g in the original brine without pre-concentration. It is proven that brine pre-concentration can enhance the adsorption effect of lithium brine extraction.

Research on redox leaching of intermediate of nickel hydroxide with synergetic effect of nickel sulfide was carried out, and optimum leaching conditions were obtained from tests, including intermediates of nickel sulfide and nickel hydroxide in a mass ratio of 1/10, initial acidity of 4 mol/L, temperature of 90 ℃, liquid and solid in a ratio of 2.0, and a reaction time of 5 h. Under such conditions, the leaching rate of manganese from nickel hydroxide can reach 99.88% and the utilization rate of nickel sulfide is also up to 79.50%. And the leaching residue can be returned as a reducing agent in the reduction and leaching of nickel hydroxide. By using this method, the consumption of both the reducing agent in leaching of nickel hydroxide and the oxidizing agent in leaching of nickel sulfide can be greatly reduced. In addition, the leaching of intermediate of nickel hydroxide can be achieved with synergetic effect of nickel sulfide, which is easy to operate and can be applied into industrial production.

With sodium bicarbonate as a precipitant, praseodymium neodymium oxide was prepared by feeding step by step in a positive sequence. The effects of pH value at the end of precipitation and precipitation temperature on particle size and impurity content of the precursor and product of praseodymium neodymium oxide were all investigated. The results show that precipitation at 50 ℃ with pH value of 5.10 at the end can prepare a praseodymium neodymium oxide powder with a median particle size D₅₀ of 21.45 μm and narrow particle size distribution. It is sphere-like powder formed by flake crystallization agglomeration, with the content of Cl^-and Na₂O at 0.017% and 0.012%, respectively, indicating higher than the national standards.

A technique of nanofiltration combined with ammonium sulfide precipitation was verified for its feasibility of separating and recovering ammonium nitrate and nickel nitrate from nickel-containing feed solution. Based on investigating the effects of pressure on the side of concentrate stream in nanofiltration, stages of nanofiltration and pH value of ammonium sulfide precipitate, an appropriate route was determined, including two-stage nanofiltration, KLNi-01 ion exchange to remove nickel, nickel precipitation with ammonium sulfide, and dissolution with nitric acid to recover nickel nitrate. The feed stream with pH of 6 was subjected to a two-stage nanofiltration, with pressure of 0.8 MPa on the side of concentrate stream. The obtained permeate stream with nickel content decreased to 0.181 g/L was adsorbed with KLNi-01 resin, leading to the nickel content therein further reduced to 0.002 mg/L. Then, 36 mL/L ammonium sulfide solution was added into the concentrate stream with an initial pH of 6 for nickel precipitation. The generated solution had nickel content of 4.7 mg/L, and no sulfide was detected, while the obtained precipitate of nickel sulfide was then dissolved with nitric acid, and the nickel nitrate solution was obtained with concentration of 258.40 g/L. The material balance calculation shows that treatment of 1 m³ of nickel-containing feed stream can generate 0.3 m³ permeate, and 192.93 L of nickel nitrate solution with concentration of 258.40 g/L can be generated with the consumption of 25.20 L of ammonium sulfide solution with concentration of 20%-26%, 37.22 L of concentrated nitric acid and 109.05 L of water.

A technique combining mechanical force and heating effect was adopted to selectively disassociate cathode material from spent lithium-ion batteries and roll the aluminum foil by adjusting processing parameters. The results show that a better disassociation effect can be obtained with the frequency of electric motor, air circulation fan and dissociation device at 40 Hz, 40 Hz and 50 Hz, respectively. The aluminum foil with particle size of -1.7+0.075 mm is rolled to be spherical, and the cathode materials with particle size of -0.075+0.048 mm and -0.048 mm are rough on the surface and wrapped by organic binder. The final dissociation rate of cathode sheet can be up to 96.35%, and the cathode material can be recovered at a rate of 94.95% by single operation, with the content of Al impurity less than 0.15%. It is shown that this selective dissociation technique based on a combination of mechanic force and heating effect can actualize an efficient separation and sorting of cathode sheet, not only shortening the battery disposal process flow but also achieving efficient metal enrichment.

An introduction of preparation method of Fe/Al₂O₃ ceramet composites is presented. The combination mechanism of Fe-base and ceramic phase in the preparation process of Fe/Al₂O₃ cermet composites, as well as the optimization of preparation technique and material properties are all expounded based on the principle of powder metallurgy. Finally, the future direction for Fe/Al₂O₃ cermet composites research is also predicted.

The cap specimens of Al_0.4 CoCrFeNi high-entropy alloy were dynamically loaded with a split Hopkinson pressure bar at room temperature, for studying the adiabatic shear sensitivity of Al_0.4CoCrFeNi high-entropy alloy at different strain rates. The results show that the grain size of Al_0.4CoCrFeNi high entropy alloy before and after dynamic loading is about 100 μm and 100 nm, respectively, with about three orders of magnitude difference. The Al_0.4CoCrFeNi high entropy alloy, with a finer grain size after dynamic loading, has lower adiabatic shear sensitivity, which will increase with the increase of strain rate. Within the range in the experiment, the adiabatic shear sensitivity reaches the highest when the strain rate is 3 360 s^-1, forming an adiabatic shear band that is about 2 μm wide and has an angle of 45° with the dynamic loading direction. At this moment, both the critical strain value and the formation energy per unit volume of adiabatic shear are the smallest. The Al_0.4CoCrFeNi high-entropy alloy undergoes significant grain refinement during high strain rate deformation. And the adiabatic shear of Al_0.4CoCrFeNi high-entropy alloy under dynamic loading is attributed to the thermal-viscoplastic constitutive instability of the material.

With micro-nano TiC as reinforcing phase and nickel powder as matrix powder, a TiC reinforced Ni-based coating was fabricated by laser cladding technology, and the effect of TiC on microstructure and wear resistance of the coating was investigated. The results show that Ni-based coating has its microstructure predominately composed of γ-Ni and TiC, and a high content of TiC is prone to cause TiC segregation at the top of coating. With the increase of TiC content, coating will have its hardness increase gradually, especially have an obvious improvement in the surface hardness. A three-body wear test shows that the wear resistance of this composite coating decreases as TiC content increases, indicating that the brittle reinforcement phase is not conducive to improving wear resistance of the coating under impact load.

After 6061-T4 aluminum alloy sheet for automobile was welded by laser welding, the microstructure, microhardness, strength and plasticity of welded joint, as well as fracture surface morphology of tensile specimen were studied by using metallographic microscope, transmission electron microscope, scanning electron microscope, Vickers hardness test and tensile test. The results show that the laser welded joint of 6061-T4 aluminum alloy has a coarse strip of grain structure in its base metal area, the weld seam has a structure of very fine as-cast dendrite in the center, acicular β″ precipitates segregate at grain boundary, and dislocation density decreases. It is found that both the strength (hardness) and plasticity of laser welded joint are lower than those of base metal.

A Fe-based cladding layer was prepared on the surface of 27SiMn steel by using laser cladding technique, and effect of preheating on the microstructure and mechanical properties of the heat affected zone (HAZ) of 27SiMn steel was investigated. The results show that a large amount of martensite appears in the HAZ of 27SiMn steel after laser cladding process. The tensile fracture is composed of river-pattern cleavage plane, tear edge and dimple, representing a quasi-cleavage fracture; preheating treatment effectively reduces the amount of martensite and brings pearlite structure. When the preheating temperature is 100 ℃, the quenched layer has its hardness decreased by 25.4%, elongation increased by 11.5%, and tensile strength decreased by 14.3%. When the preheating temperature rises to 300 ℃, ductile fracture occurs in the material under tensile force. Appropriate preheating can effectively reduce the martensite in the HAZ of 27SiMn steel and alleviate the decline in the toughness of 27SiMn steel caused by quenching, thus improving the safety during the service of hydraulic cylinder made of laser cladded 27SiMn steel.

A surfacing layer of Babbitt alloy was prepared on the surface of steel 20 by cold metal transfer (CMT) welding. And the metallographic morphology, phase composition, microstructure, element distribution, hardness and friction coefficient of the surfacing layer were analyzed by using metallographic microscope, X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, Vickers hardness tester, as well as friction and wear tester. The results show that the phase structure of surfacing layer of Babbitt alloy does not change and is composed of hard point SnSb phase, Cu₆Sn₅ phase and soft matrix α-Sn phase. A lower heat input leads to a rapid cooling rate for the surfacing layer of Babbitt alloy, and the surfacing layer with a finer grain size has hardness around 40HV_0.1, much higher than that of cast Babbitt alloy. As the microhardness increases, the friction coefficient and specific wear rate of Babbitt alloy fall down to 0.31 and 1.38 × 10^-5 mm³/(N·m), respectively. Based on the study of the wear mechanism, it is found that the surfacing layer of Babbitt alloy principally experiences abrasive wear. CMT welding can effectively improve the hardness and wear resistance of Babbitt alloy.

In order to protect ecological environment during exploitation of coal resources in lake, a mining mode with distributed ecosystem was developed for lake mining area, and the function mechanism of such system was explored. In such mode of lake mining, an ecosystem is composed of six subsystems, including biological function system, ecological water treatment and utilization system, ecosystem development and utilization system for land resources, organic fertilizer processing system, integrated energy utilization system, and ecosystem utilization system for solid waste resources. These subsystems can not only function alone but also interact with each other, thus forming mechanisms for life cycle, metabolism, balance, combination, sharing and cooperation. With these mechanisms as the theoretical basis for the distributed ecosystems in lake mining area, effective exploitation of lake resources, sustainable development of ecological environment, as well as promotion of economic benefit from lake resources mining can be actualized by recycling the resources among those six distributed subsystems. This study can provide reference for underwater coal resources mining while ensuring ecological conservation.