Eight groups of WC-12%Co cemented carbides with different carbon contents were prepared by mixing,pressing,and hot isostatic pressing sintering.The influences of carbon content on the microstructure and mechanical properties of the cemented carbides were analyzed using metallographic microscope,scanning electron microscope,hardness tester,and electromechanical universal test machine.The results show that the WC-12%Co cemented carbides with carbon contents of 5.26%~5.42%are in the WC+γtwo-phase zone.When the carbon content is less than or equal to 5.22%,the cemented carbide exhibits flocculent and needle like decarburization phases.When the carbon content is greater than or equal to 5.46%,black flocculent carburized phase appears in the cemented carbides,accompanied by the appearance and aggregation of coarse grains and the segregation of cobalt.As the carbon content gradually increases,the WC grains gradually grow larger,the crystallization tends to be complete,the grain edges tend to be straight,and the grain boundaries become clearer.When the carbon content reaches 5.54%,rounded corners appear at the edges of the WC grains.The cemented carbides with carbon contents of 5.26%~5.42%are in WC and Co two-phase zone,exhibiting superior comprehensive mechanical properties,with hardness maintained at 1777~1695 kg/mm² and bending strength of 3357~3290 MPa.

YG6 fine-grained cemented carbides with different amounts of Mo₂C were prepared by traditional powder metallurgy method.The influence of Mo₂C addition amount on the microstructure and properties of YG6 fine-grained cemented carbides was studied by observing the microstructure and testing the physical and mechanical properties.The results show that with the increase of Mo₂C addition,the grain size of WC in the alloy becomes finer and stablizes.When the addition of Mo₂C in the alloy exceeds 3.5%,it has spheroidizing effect on the morphology of WC grains.In addition,the addition of Mo₂C reduces the density of the cemented carbides,while the coercive force increases with the increase of Mo₂C content.When Mo₂C addition amount is 5.0%,the cemented carbides exhibit the best comprehensive mechanical properties,with hardness of 92.7 HRA,bending strength of 3600 MPa,and abrasive wear value of 0.81 cm³/(10⁵r).

WC-Ni based cemented carbides were fabricated by vat photopolymerization(3D printing)technology.The influence of slurry composition and printing parameters on the rheological and curing properties of the slurry was investigated,as well as the properties of WC-Ni based cemented carbides.The results indicate that when the solid content of the slurry is 40 vol.%and ZN-1344 is chosen as the dispersant with an addition of 2%by mass of the powder,the rheological properties of the WC-Ni slurry meet the requirements of the additive manufacturing process.And the viscosity of the slurry reaches 2.718 Pa·s at a shear rate of 100 s^-1.When the printing parameters are set to 0.01 mm hatch spacing,90%laser power,and 2000 mm/s scanning speed,the maximum single-layer curing depth of the slurry reaches 144μm.The calculation model for the single-layer curing depth of the slurry is obtained by data fitting using the response surface methodology(RSM),and the calculated value has a deviation of 3.4%compared with the actual value,demonstrating its capability of theoretical prediction.The density and relative density of WC-15%Ni cemented carbide prepared via vat photopolymerization can reach a maximum of 13.51 g/cm³ and 96.5%,respectively.The addition of 1 wt.%grain growth inhibitor Cr₃C₂ significantly improves the Vickers hardness of the cemented carbide to 945 HV₃₀,approaching the hardness of traditional cemented carbides with equivalent Ni content but without Cr₃C₂.

CoCrFeMnNi high-entropy alloy powder with equal molar ratio was prepared by mechanical alloying,and WC-10CoCrFeMnNi cemented carbide was prepared by spark plasma sintering.The microstructure and properties of high-entropy alloy powder and cemented carbide were studied by X-ray diffractometer,scanning electron microscope,energy dispersive spectrometer,Vickers hardness tester,and laser particle size analyzer.The results show that the nanocrystalline CoCrFeMnNi high-entropy alloy powder,with BCC as the main phase and FCC as the secondary phase,can be obtained by 80 h of ball milling.The ave-rage particle size is 1.4μm,and the particle size distribution is relatively centralized.The cemented carbide,using CoCrFeMnNi high-entropy alloy as the binder phase,exhibits excellent mechanical properties.And the cemented carbide sintered at 1250℃has better comprehensive mechanical properties,with a Vickers hardness of(1452±18.95)HV₃₀and a fracture toughness of(8.57±0.32)MPa·m^1/2.

FeCoNi medium-entropy alloy exhibits excellent properties compared with traditional alloys,but its room temperature strength is not high,which limits its application.The blocks of FeCoNiTi_x(x=0,0.25,0.50,0.75,1)medium-entropy alloy were prepared by mechanical alloying and spark plasma sintering.The effects of mechanical alloying sequence of each element and Ti content on the microstructure and properties of FeCoNiTi_x medium-entropy alloy were emphasized.Additionally,preliminary exploration was conducted on the application of FeCoNiTi_x medium-entropy alloy as binder in WC-based cemented carbides.The results show that the FeCoNi matrix phase is FCC phase during mechanical alloying,and the addition of Ti element results in the formation of Laves phase and titanium oxide phase.Therefore,the phase of FeCoNiTi_x medium-entropy alloy consists of FCC phase,Laves phase and titanium oxide phase.With the increase of Ti content,the density,hardness and strength of FeCoNiTi_x alloy increase,while the plasticity increases at first and then decreases.The FeCoNiTi_0.50medium-entropy alloy exhibits good mechanical properties,and its microhardness,yield strength,compressive strength and compressive strain are 531 HV,1987.57 GPa,2114.85 GPa and 20.5%,respectively.The addition of a small amount of Ti element can enhance the corrosion resistance of FeCoNi alloy.FeCoNiTi_x binder can exist stably in WC-based cemented carbides,inhibiting the formation of decarburization phase in the sintering process of WC.WC-FeCoNiTi_0.50cemented carbide exhibits good mechanical properties,and its microhardness and fracture toughness are 1834 HV and 15.12 MPa·m^1/2,respectively.

A dual hard phase material,Cr₃C₂-WC-NiCoCrMo thermal spraying powder,was prepared by agglomeration-sintering method,with the coating prepared by utilizing high-velocity oxygen-fuel(HVOF)spraying technology.And the effects of powder microstructure and oxygen-fuel ratio(λ)of thermal spraying on the microstructure and properties of the coating were studied.The results show that with an increase in sintering temperature,the apparent density and fluidity of the powder increase,leading to a denser microstructure.Under the condition of a fixed oxygen-fuel ratio of 1.09 during thermal spraying,the comprehensive performance of the prepared coating is relatively excellent when the sintering temperature of the spraying powder is 1295℃,with its microhardness of(1135.8±40.7)HV_0.3and porosity of 1.1%±0.1%.And under the condition of a fixed sintering temperature of the spraying powder of 1295℃,the prepared coating with the oxygen-fuel ratio of 1.0 during thermal spraying has the optimal comprehensive performance,with a microhardness of(1145.8±39.6)HV_0.3,a deposition efficiency of 48.8%,and a porosity of 1.0%±0.1%.

随着人民生活水平的提高,投资理财已经成为许多家庭实现财富增长与资产管理的重要途径。然而,近年来层出不穷的非法集资事件也提醒人们投资前需擦亮眼睛,理性分辨理财活动是否合法,保护财产安全。一、明辨非法集资风险目前,非法集资活动伪装成各类理财产品吸引投资者,上当受骗事件层出不穷。

Vanadium is usually associated with other metals as a rare metal.A large number of impurity ions,such as iron,could exist in the sulfuric acid leaching solution of vanadium-bearing ore,which significantly impacts the subsequent separation and enrichment of vanadium.The study of extraction kinetics is an important method for determining the control steps in the extraction process,and the difficulty in extracting metal ions.A self-designed cylindrical constant interface cell was used to study the kinetics of extracting V(Ⅳ)and Fe(Ⅱ)from sulfuric acid solution with P507 as the extractant.The results show that the aqueous phase serves as the diffusion resistance zone of the extraction process,which is a chemical reaction-controlled type.The extraction rates of V(Ⅳ)and Fe(Ⅱ)both demonstrate an upward trend with the increase of stirring speed and extraction temperature.The apparent activation energy of V(Ⅳ)extraction is 48.68 kJ/mol,and that of Fe(Ⅱ)extraction is 135.11 kJ/mol.P507 is more likely to extract V(Ⅳ)from sulfuric acid solution,presenting the potential to achieve the efficient separation of V(Ⅳ)from Fe(Ⅱ).

W-Cu composites are widely used in various industrial fields due to their excellent comprehensive properties, including high hardness, wear resistance, ablation resistance, electrical and thermal conductivity, and low thermal expansion coefficient.This paper introduces the latest research progress of W-Cu compo-sites and their current applications in electrical contacts, microelectronics, military use, and functionally graded materials.In addtion, the paper emphatically summarizes and analyzes the classification and principles of doping modification for W-Cu composites, as well as the influence of doping modification on material properties.Finally, the potential problems and research directions of W-Cu composites in the future are put forward.

The W-6Ni-4Co-2X alloys(X=Nb,Ta,Hf,Mo and Ti)were prepared by powder metallurgy technology,and the effects of adding Nb,Ta,Hf,Mo,and Ti elements on the microstructure and mechanical properties of W-6Ni-4Co alloy were investigated.The results show that the microstructure of the W-6Ni-4Co-2X alloys mainly includes base phase(W phase)and binder phase,and the type and content of the binder phase are related to the precipitation of dissolved W phase in the binder phase(Ni,Co)during sintering.The W grains of W-6Ni-4Co-2Ta alloy and W-6Ni-4Co-2Hf alloy are in the form of irregular polygon,while the W grains of W-6Ni-4Co-2Nb alloy and W-6Ni-4Co-2Ti alloy are ellipsoidal and dispersedly distributed in the binder phase.The uniform microstructure,finer grains,and good interfacial bonding of the W/binder phase in W-6Ni-4Co-2Ta alloy contribute to its superior hardness,bending strength,and yield strength.In W-6Ni-4Co-2Mo alloy,W grains are arranged in network structure,and the continuous W ske-leton structure,in synergy with the ductile binder phase,reduces the strain hardening of the alloy,contributing to its excellent strain hardening resistance.Therefore,adding suitable transition metal elements to W-6Ni-4Co alloy provides an effective way for improving its mechanical properties.