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.