The effects of different content of interstitial carbon atoms on the microstructure and properties of Fe₅₀Mn₃₀Co₁₀Cr₁₀ as-cast high-entropy alloy were analyzed by means of XRD,OM,EBSD and SEM.The results show that phase composition of the as-cast alloy changes from FCC+HCP two phases to FCC single phase with the increase of carbon content.The Cr_xC_y carbide precipitates in the grain boundary and within the grains of the matrix when the molar fraction of carbon atoms reaches 4%,which deteriorates the ductility of the alloy.When the molar fraction of carbon atoms is 2%,(Fe₅₀Mn₃₀Co₁₀Cr₁₀)₉₈C₂ high-entropy alloy has the best comprehensive mechanical properties due to the obvious TWIP effect.

High purity SiC powder for single crystal growth was synthesized by self propagating method in vertical reaction chamber and horizontal rotating drum chamber,respectively,and 4 H-SiC single crystal was grown by using the synthesized high purity SiC powder.The crystal orientation,crystal form and purity of the synthesized powder were studied by bulk density test,XRD,Raman and GDMS.The morphology and crystal form of the grown 4 H-SiC single crystal were characterized to verify the applicability of the synthesized powder.The results show that when the synthesis process of high-purity SiC powder is carried out in the horizontal rotating drum chamber,the synthesized SiC powder has stable crystal form and good crystal quality,which meets the needs of growing 4 H-SiC single crystal.Compared with the vertical reaction chamber,the synthesis efficiency in the horizontal rotating drum chamber is increased from 87.8% to 98.7%.

Taking the two groups of WC-11.2Co-0.3TaC cemented carbide with or without H2 during the process of secondary sintering as the research object,the influence of H2 on the microstructure and properties of the alloy after pre-sintering was studied by metalloscopic observation and physical and chemical properties testing.The results show that the oxygen content of the pre-sintered sample at 850℃ is affected by the storage time.With the prolongation of the storage time,the oxygen content of the sample gradually increases.After the storage time is more than 12 h,the oxygen content is basically stable at about 0.22%.H₂ intervention during the secondary sintering can better protect the carbon content in WC-11.2CO-0.3TaC cemented carbide,so that its relative magnetic saturation strength is maintained at about 94.9%.The higher carbon content leads to more ununiform WC grains in the alloy,and at the same time leads to a decrease in density,hardness,coercive force and bending strength of the alloy.Compared with the secondariy sintered sample without H₂,the flexural strength of the sample with H₂ is reduced by 604 N/mm².

The effects of carbon content,WC grain size,microporous structure,sintering temperature,heat treatment process,etc.on the friction properties of WC coarse-grained cemented carbide are reviewed.Through analysis,it is found that as the carbon content gradually increases,the friction properties of WC coarse-grained cemented carbide firstly increases and then decreases.When the WC coarse-grained cemented carbide has a microporous structure,excellent friction properties can be obtained.Appropriately increasing the sintering temperature can increase the free path of Co and contribute to the stability of the coarse-grained WC framework.The lower the Co content,and the larger the size of the coarse WC grains,the better the friction properties of the WC coarse-grained cemented carbide.Based on analysis,it is also found that the heat treatment process can effectively improve the friction properties of WC coarse-grained cemented carbide.

The effects of electromagnetic enhancement treatment on physical properties,microstructure,residual stress and cutting performance of cemented carbide coated tools were studied.The results show that electromagnetic enhancement has no obvious effect on the magnetic and mechanical properties of cemented carbides,but the tool life is increased by 18.9%,and the flank wear loss of the tool is reduced by 27% for the same cutting time.The residual stress of the tool was measured by XRD.And the results show that electromagnetic enhancement reduces the residual stress of the cutting edge.The microstructure of the tool was characterized by SEM.And it is found that the density of the material is improved by electromagnetic enhancement,and the number of microcracks is reduced,which can improve the anti-collapse ability of the tool.In addition,the spherical nano-oxide particles adsorbed on the cutting surface of the electromagnetically enhanced tool play a role in reducing friction and improving the wear resistance of the tool.

在各种灾害中,火灾是最经常、最普遍地威胁公众安全和社会发展的主要灾害之一。火灾不仅毁坏物质财产,造成社会秩序的混乱和生态平衡的破坏,还直接或间接危害生命。每个人对自己工作、学习或居住场所的结构及逃生路径要做到了然于胸,同时在生活中也要时时处处防火,掌握基本的消防安全常识。

Simulated in-situ leaching tests of ionic rare earth ore were carried out,and the influences of type,concentration,pH value and flow rate of the leaching agent,solid-liquid ratio and temperature on RE and Al leaching rate were investigated.The results show that the average leaching rates of RE and Al are 94.56%and 45.10%,respectively,using ammonium sulfate as the leaching agent with concentration of 2%,pH va-lue of 4.50 and flow rate of 10 mL/min,and under the leaching conditions of solid-liquid ratio of 1∶0.66 and room temperature.The results of extended leaching test show that the leaching rate of RE and Al are 94.58%and 45.96%,respectively,realizing the high-efficiency leaching of RE,while the impurity Al is less leached.

High-concentration Pr-NdCl3 feed solution separated from Bayan Obo rare earth concentrate by smelting contains 0.10~0.34 g/L aluminum,and the aluminum content directly affects the quality of downstream products,so it is necessary to separate aluminum from rare earth.Based on the principle of preferential extraction of aluminum in naphthenic acid-isooctanol-sulfonated kerosene system,the non rare earth impurity aluminum can be removed from high-concentration Pr-NdCl3 feed solution by cascade extraction separation process.The pilot scale test was carried out based on the analysis and demonstration of the whole technological process and the cascade extraction and cascade washing process.The results show that after 30-stage cascade extraction separation process,the concentration of REO is more than 220 g/L,the content of aluminum impurity is greatly reduced,the mass ratio of Al2O3 to REO is less than 7.8×10-5,and the product quality meets the standard.The application of cascade extraction separation process not only optimizes and improves the existing single-stage extraction process,but also improves and stabilizes the product quality,having promotion value.

In view of the long recovery process and low lithium recovery rate of waste ternary power batte-ry,and the situation that most enterprises only produce crude lithium carbonate and lithium phosphate,and the added value of products is low,the lithium extraction process of flotation-reduction roasting carbonization is used to produce battery grade lithius carbonate.The results show that under the optimized process index and device sign parameters,the recovery rate of lithium is more than 90%.The removal of most ne-gative graphite by flotation can effectively reduce the specifications of leaching equipment and pressure filtration equipment,shorten the subsequent recovery process of nickel,cobalt and manganese,and reduce the acid and alkali consumption in the extraction process.The impurity content of the solution after lithium extraction by carbonization is low,and the battery grade lithium carbonate can be produced after purification,which can improve the economic benefit of the enterprise.