The effect of ultrasonic melt processing time on the microstructures and hardness of as-cast and homogenized Al-Cu-Mg-Ag-Fe-Ni alloys was studied. The results show that ultrasonic melt processing leads to more uniform distribution of Fe/Ni-rich phases. Two-minute ultrasonic processing can result in grain refinement of the alloy. However, ultrasonic processing, if extended to 6 minutes, will result in grain coarsening. It is found that ultrasonic processing promotes the dissolution of Al₂Cu phase and enhances the solid-solution strengthening effect, resulting in improvement in hardness of the as-cast alloy. After homogenization, Fe/Ni-rich phase is detected as the residual secondary phase in the structure, which exhibits discontinuous distribution along the grain boundaries after ultrasonic processing.

Influence of Al content on the microstructure, phases, hardness, tensile and impact properties of quenched and tempered 4Cr5MoVSi die steel was studied by using optical microscopy, transmission electron microscopy (TEM), tensile testing machine among other instruments. It is found martensite is formed in the quenched and tempered 4Cr5MoVSi die steel with Al content of 0-0.6% (mass fraction, the same below), while martensite plus δ ferrite are formed in the quenched and tempered 4Cr5MoVSi die steel with Al content of 1.2%-1.8%. Without adding Al or with an addition of 0.3%-1.8% Al, 4Cr5MoVSi die steel after quench and tempering has α-Fe and M₇C₃ formed as its main phases. The 4Cr5MoVSi die steel with an Al content of 0.3%-1.2% has its relatively small variation in its hardness after quenching and tempering; however, with Al content up to 1.8%, the quenched and tempered die steel has its hardness significantly reduced. It is concluded that an appropriate addition of Al is beneficial to improvement in the room-temperature tensile strength, elongation at break, and impact toughness of quenched and tempered 4Cr5MoVSi die steel; with an addition of 1.2% Al, the quenched and tempered 4Cr5MoVSi die steel can have higher hardness, strength, and impact toughness.

To investigate the rheological properties of heat-treatment-free AlSi9MnMg alloy specifically for high-pressure die casting (HPDC) process, influence of temperature and shear rate on the viscosity of molten alloy was studied by using a rotational rheometer based on the Searle principle, and the microstructure of the samples in rheological testing was analyzed. The results indicate that the viscosity of molten alloy decreases as the temperature rises in the test. At a given temperature, the viscosity decreases as the shear rate increases. With the shear rate exceeding 800 s^-1, the viscosity remains unchanged with shear time at the same shear rate. Under the action of shear force, the dendritic grains in the melt undergo fragmentation, agglomeration and spheroidization. Moreover, as the temperature rises in the test, the particle agglomerates become smaller in size.

Based on the Derwent Innovations Index (DII), the technologies for recycling cathode materials in spent lithium-ion batteries were analyzed in terms of patent indicators, including the number of patent applications and patent holders, the number of priority rights in countries/regions, patent citations, patent H-index among others. It is found that the recycling technologies are in rapid development, and the Chinese research organizations have created a patent portfolio plan, including a large number of high-quality patents that can improve competition. Over the past five years, the technologies, including pretreatment processes of discharge and separation, recovery of lithium, nickel, cobalt and manganese, extraction of precious metals by hydrometallurgical and pyrometallurgical processes, as well as recycling equipment, have become hotpots in this field. China has a relatively large number of core patents, mainly involving hydrometallurgical process, direct recycling process, and a combination of pyrometallurgical and hydrometallurgical processes. Finally, some countermeasures and suggestions are proposed for enhancing the competitiveness of China's industry in recycling cathode materials in spent lithium-ion batteries, which provides references for promoting the healthy development of China's lithium battery recycling industry.

For phosphorus-iron waste left after lithium extraction from cathode powder of spent lithium iron phosphate (LFP) batteries, a selective leaching with sulfuric acid was adopted to remove impurities therein. The results indicate that after a 4-stage leaching at 80 ℃ for 2 h, with a sulfuric acid at a concentration of 0.32 mol/L and a liquid-to-solid ratio of 5 mL/g, the total leaching rates of elemental impurities, including Cu, Mn, Al, Ca, Na and Mg reach 70.81%, 68.33%, 65.57%, 68.03%, 67.85% and 64.28%, respectively, and the total leaching rates of P and Fe are only 2.52% and 2.24%, respectively. It is concluded that the main elemental impurities can be effectively leached out from such phosphorus-iron waste, with elements of P and Fe left for subsequent resource utilization.

The mechanical properties and energy evolution law of dolomite under a combined action of dry-wet cycle and cyclic loading and unloading were explored. The results show that the structural damage caused by dry-wet cycles leads to the transformation of dolomite from brittle fracture to ductile fracture, which is manifested by an increase in the area of hysteresis loops and a decrease in peak strength. At the early stage of cyclic loading and unloading, a strengthening effect is observed, and then the dolomite develops into the strain-softening and damage stages. An energy analysis indicates that the total input energy is mainly stored in the form of elastic strain energy, and the proportion of dissipated energy increases slowly with the accumulation of damage. Additionally, based on the variation of the damage variable defined by dissipated energy, the damage evolution tends to be stable after a progressive and accelerated process.

Based on the characteristics of the exploration contracts approved by the International Seabed Authority (ISA), the global competition status and variation trend of the exploration contract areas are analyzed in terms of temporal changes, spatial distribution and mineral types. Based on the analysis results, strategies to cope with the variation in the situation of ISA exploration contract areas are proposed, including commercial companies acting as the main players, strengthening international cooperation with African countries and the Enterprise of ISA, giving priority to exploration of polymetallic nodules, cultivating advantageous contractors and safeguarding the rights and interests of contractors.

A 3D heterogeneous numerical model was established based on the C6^# mining area of the Bayan-Uul uranium deposit to analyze the effects of different horizontal permeability in the filter section on solute transport, pH value and uranium mineral leaching performance. The simulation results show that after 450 days, the uranium leaching rate is 13.56% at the vertical depth of 30 m in the filter section, presenting 22.71% higher compared to the leaching rate of 11.05% at the depth of 35 m. According to the sandstone permeability, grade of uranium in the stratum and heterogeneity, the vertical arrangement position and length of filter section can be optimized, so as to effectively improve the economically recoverable metal quantity.

To investigate the fracture characteristics of rocks with bent cracks under saturated condition, uniaxial compression tests were conducted for rock specimen with different inclination degrees and numbers of crack bends under saturated conditions to study load-displacement curves, peak strength, acoustic emission characteristics, crack initiation modes, and penetration modes of the rock specimen. The results show that the load-displacement curve of saturated rock specimen with bent cracks presents one-peak or double-peak shape, with peak strength increasing after an initial decreasing as the crack inclination angle becomes larger. The acoustic emission signals become stronger as the crack inclination angle becomes larger and the number of crack bends increases. Cracks mainly initiate at the tip and bends, and mainly penetrate directly or run without penetration.

To explore the impact of near-surface ore body mining on the stability of overburden and dangerous rock masses of slopes, a phosphate mine was taken as an engineering project in the study. The stability of the dangerous rock mass of the slopes was determined by on-site investigation, and the evolution of deformation, stress and plastic zone of overburden under different mining schemes were simulated with FLAC^3D software. The research results indicate that structural planes between layers of surrounding rock on the roof of stope are well-developed, probably causing falling debris in blocks or flakes. The strata are hard and brittle in lithology and have developed rock fractures. Under unloading effect of high and steep slopes, dangerous rocks are prone to be separated along the combination of fractures and strata plane, forming dangerous rock masses. The response law of the maximum stress in the overburden is similar to the law of the unbalanced force in numerical calculation. There is relatively small disturbance generated during mining process, which brings a little impact to the stability of adjacent stopes and surface. It is found that the ground surface is less affected by underground mining, with the deformation within the maximum limit value specified in the standard. If Ph2^# ore body is mined after Ph1^# ore body, the overburden can have relatively small displacement, and no connectivity in the plastic zones is occurred in the mining pillars, stopes and overlying strata.