A FeCoCrNiMn high-entropy alloy (HEA) coating was prepared on the 201 stainless steel surface by adopting high-speed laser cladding technology, and then the microstructure, phase distribution, microhardness of FeCoCrNiMn coating, as well as its wear properties in dry sliding condition were all investigated. It is found that such laser cladded FeCoCrNiMn HEA coating consists of a single FCC structure, with no obvious cracks observed. It also forms a good metallurgical bond with the substrate. The microhardness of the coating is around (439±2.1) HV, nearly two times that of 201 stainless steel substrate, and the strengthening mechanisms mainly include strengthening by grain refinement and solid solution strengthening. Also, the FeCoCrNiMn coating presents an obviously better wear resistance than 201 stainless steel, with an average friction factor of 0.246 and a specific wear rate of about 2.59×10^-6 mm³/(N·m). The wear mechanisms for it include adhesive and abrasive wear. It is concluded that such FeCoCrNiMn HEA coating prepared by high-speed laser cladding technology can significantly improve the surface hardness, wear resistance and service life of machine components.

The effect of water splat cooling assisted friction stir welding (WCaFSW) on the structure, texture and mechanical properties of aluminum alloy welding joints were investigated by means of optical microscopy, scanning electron microscopy and a tensile testing machine. The results show that compared to normal friction stir welding (FSW), WCaFSW can lead to grains in weld nugget zone (WNZ) with significantly reduced size and grains in all regions of WNZ with more uniform size, and a higher percentage of high-angle grain boundaries. The WNZ of FSW joints have and B shear texture, while the WNZ of WCaFSW joints have and C shear texture. Compared to FSW joints, WCaFSW joints have higher tensile strength and lower elongation rate. And ductile fracture is the main failure mode in both WCaFSW and FSW joints.

In order to improve the strength-ductility balance of medium manganese steel for automobiles, cold-rolled medium manganese steel was treated by annealing at different temperatures (650-680 ℃) and for different time (10-50 min) for austenitic reverse transformation. Then, effects of annealing temperature and holding time on the microstructure and mechanical properties of medium manganese steel were explored. It is found that the microstructure of the original cold-rolled medium manganese steel plate is composed of ferrite (F) and martensite (M), and the dispersed carbides with sizes ranging from 20 nm to 45 nm can be observed in the microstructure. As the annealing temperature rises from 650 ℃ to 680 ℃, the yield strength, elongation, strength-ductility balance, and residual austenite volume fraction of medium manganese steel increase followed by a decrease, but tensile strength increases all the time. As the annealing time is prolonged from 10 min to 50 min, the yield strength, tensile strength, elongation, strength-ductility balance and residual austenite volume fraction of medium manganese steel decrease after an initial increase. It is found that after annealing treatment at 660 ℃ for 30 min, the cold-rolled medium manganese steel has a structure composed of F + M + austenite (γ), with austenite at a volume fraction of 24.12%, ultrafine grained ferrite with an average grain size of 0.29 μm, lath martensite with an average wideness of 0.27 μm, and strength-ductility balance of 23.33 GPa·%.

In order to investigate the main factors affecting the service life of graphite anodes used in preparation of rare earth metals, a range of analytical tools, including a digital microscope, an optical microscope, an SEM, XRD, a simultaneous thermal analyzer and a four-probe tester were employed for comparison and comprehensive evaluation of macroscopic and microscopic morphology, crystal structure, graphitization, thermal properties and resistances of graphite anodes with different service lives. The results indicate that the resistance, internal cracks and porosity of graphite anodes contribute mainly to the difference in the service life of graphite anodes. The research results can be of reference for selection of graphite anode in preparation of rare earth metals, thus providing technical assistance for enterprises to realize cost reduction and efficiency improvement.

The expanded graphite (EG) derived from the graphite anodes of spent lithium-ion batteries was taken as conductive substrate, and then Sn/Co-based bimetallic sulfide was loaded by using a hydrothermal method to synthesize SnCoS₄@EG nanocomposite. And such EG presents a cross-linked porous three-dimensional lattice, and the SnCoS₄ nanocrystals in the synthesized composite are uniformly dispersed in the EG, which enhances electrical conductivity of electrode material and stability of metallic sulfide, but also increases the contact area between active sites and electrolyte, leading to a higher exchange rate of Li⁺ ions at electrode/electrolyte interface. It is shown that SnCoS₄@EG electrode can exhibit a reversible specific capacity of 1 195.90 mAh/g at 1.0 A/g after 500 cycles, presenting excellent durability over a large number of cycles.

High-strength and high-conductivity Al-0.65Mg-0.58Si-0.17Fe alloy wire was prepared by adopting horizontal continuous casting process followed by continuous extrusion and drawing processes, and effects of such processing technique and heat treatment on microstructure, mechanical properties and conductivity of the prepared alloy were investigated. The results show that the processing technique of horizontal continuous casting plus continuous extrusion can improve the solid solubility in supersaturated alloy and lead to significantly grain refinement, and the following drawing process introduces high-dense dislocation, which changes the precipitation behavior of Mg₂Si phase during the ageing treatment of the alloy. It is shown that Al-0.65Mg-0.58Si-0.17Fe alloy prepared by the processes of horizontal continuous casting, continuous extrusion and drawing is subjected to 3 hours of aging treatment at 155 ℃, resulting in its tensile strength of 335 MPa, elongation rate of 6.9%, and electrical conductivity of 55.7%IACS.

Surface mechanical attrition treatment (SMAT) was adopted for low-carbon steel materials to achieve surface nanonization, and then the influence of surface nanonization on corrosion resistance of low-carbon steel was also discussed. The results show that due to surface nanonization, the low-carbon steel has a greater plastic deformation on the surface as the carbon content decreases, and the X-ray diffraction of its surface presents obviously wider peaks. It is found that after nanosizing treatment for the surface of low-carbon steel with different carbon content, the lower the carbon content, the rougher the surface and the worse the corrosion resistance.

Based on an introduction of the structural characteristics of single-crystal Ni-rich ternary cathode material, the common preparation techniques of such material are summarized. Besides, the main strategies for improving the performance of this material in recent years are also discussed, which can provide a reference for large-scale production of such high-performance single-crystal Ni-rich ternary cathode material.

To improve the interfacial stability of spinel phase LiNi_0.5Mn_1.5O₄ cathode material in deeply charged state, a nanoscale Al₂O₃ film was deposited on the surface of single-crystal LiNi_0.5Mn_1.5O₄ by atomic layer deposition in a controlled manner. The modified cathode material exhibits excellent long-cycle performance and corrosion resistance (with capacity retention rate up to 94.7% after 500 cycles at 1C). The surface and interface analysis shows that the nanoscale Al₂O₃ coating deposited by atomic layer deposition technology can significantly inhibit the corrosion reaction between material and electrolyte, and also constrain the irreversible dissolution and precipitation of transition metal ions. In addition, AlF₃ produced by HF surface etching can enhance corrosion resistance of LiNi_0.5Mn_1.5O₄ cathode material, which can thus improve its long-cycle performance and the service performance at high voltage.

A cathode material (NaNi_0.5Mn_0.5O₂) for sodium-ion batteries was synthesized by adopting solid-state, co-precipitation and sol-gel methods, and the effects of synthesis methods on crystal structure, microscopic morphology and electrochemical performance of the cathode material were also explored. The results show that the materials synthesized respectively by those three methods all have O3-type structure, but exhibit different morphology. The cathode material synthesized by solid-state method has a special layered structure, which is conducive to sodium ion de-intercalation. The cathode materials synthesized by solid-state, co-precipitation and sol-gel methods, respectively, deliver an initial specific discharge capacity of 96.1 mAh/g, 92.8 mAh/g and 92.3 mAh/g at 0.1C, with retention rate of 64.3%, 46.5% and 36.5% respectively after 100 cycles at 0.5C. It is concluded that the solid-state synthesis is an appropriate method.