A series of(Sm_1-xY_x)₂Co₁₇ melt-spun ribbons with different Y doping contents were prepared by the melt spinning method.XRD was employed to characterize the phase compositions of both the(Sm_1-xY_x)₂Co₁₇ alloy and its corresponding melt spun ribbons,while VSM was utilized to measure the magnetic properties of the ribbons.The results show that the(Sm_1-xY_x)₂Co₁₇ melt-spun ribbons mainly consist of(Sm,Y)₂Co₁₇ single phase.After melt spinning,the diffraction peak intensity of the(001)crystal plane is significantly enhanced,manifesting a distinct preferred orientation.The Sm₂Co₁₇ melt-spun ribbons fabricated at a spinning speed of 35 m/s exhibit the optimal magnetic properties,with a coercivity of 1022.5 Oe and a remanence of 29.3 emu/g.In addition,the easy magnetization direction of these ribbons is along the c-axis.With an increase in Y doping content,the magnetocrystalline anisotropy of the(Sm_1-xY_x)₂Co₁₇ melt-spun ribbons decreases,which consequently leads to a gradual reduction in both coercivity and remanence.

The morphology,quantity and size of TiN inclusions in BT490XT automotive body steel exert a significant influence on its corrosion resistance.In this work,a combined approach of experiments and firstprinciples calculations was adopted to systematically investigate the modification mechanism of rare earth Ce on TiN inclusions in BT490XT steel.The evolution laws governing the occurrence state,micromorphology,elemental distribution,and size of TiN inclusions before and after Ce addition were explored.Meanwhile,the effect of Ce-modified TiN inclusions on the corrosion resistance of the steel was evaluated via computational analysis,and the electrochemical corrosion behavior of the steel with and without Ce addition was comparatively characterized.The results show that in the absence of rare earth Ce,the dominant inclusions in the steel are single TiN inclusions and Al₂O₃-TiN composite inclusions,which are large in number and irregular in blocky shape.After the addition of 0.0019%(mass fraction)rare earth Ce,the two types of TiN inclusions in the steel are transformed into CeAlO₃-TiN composite inclusions,accompanied by a reduction in quantity and a decrease in average size from 2.72μm to 2.32μm.The modification mechanism of Ce on TiN inclusions is as follows:Al tends to combine preferentially with Ce to form CeAlO₃,which precipitates prior to Al₂O₃.The precipitated CeAlO₃ serves as heterogeneous nucleation sites,inducing the precipitation of TiN phase at its periphery and further facilitating the growth of CeAlO₃-TiN composite inclusions with a core-shell structure and reduced particle size.First-principles calculations reveal that the electron work functions of different TiN crystal planes are not identical.When the exposed surfaces of TiN inclusions are the(100)and(110)crystal planes,as well as the Ti-atom-terminated surface of the(111)crystal lographic plane,TiN inclusions act as the anode and are susceptible to corrosion.In contrast,when the exposed surface is the N-atom-terminated surface of the(111)crystal lographic plane,the steel matrix surrounding the inclusions acts as the anode and undergoes preferential corrosion.After Ce addition,the electron work function of CeAlO₃ formed in the steel is closer to that of the steel matrix,and both the potential energy difference and fluctuation degree between CeAlO₃ and the steel matrix are lower than those between TiN and the matrix.Consequently,the smaller-sized CeAlO₃-TiN composite inclusions are less likely to induce pitting corrosion than pure TiN inclusions,thus effectively improving the corrosion resistance of the steel.Electrochemical corrosion tests confirm that the steel with Ce addition exhibits a lower self-corrosion current density and superior corrosion resistance,which is in good agreement with the results derived from first-principles calculations.

Ce-based catalysts possess high oxygen storage capacity and excellent high-temperature thermal stability,showing outstanding performance in denitration reactions.To address the issue of poor low-temperature adsorption activity of Ce sites in the CePO₄-H(hexagonal cerium phosphate)catalyst toward NH₃ and NO molecule,Cu-doped CePO₄-H catalysts were prepared by impregnation method.The effects of varying Cu contents on the denitration performance and phase composition of the catalysts were investigated.Based on the first-principles density functional theory(DFT),the adsorption behaviors of NH₃ and NO during the NH₃-SCR reaction on the Cu-doped CePO₄-H(100)crystal plane were systematically studied by the PBE functional.The experimental results show that the CePO₄-H catalysts before and after Cu doping exhibit the characteristics of typical hexagonal CePO₄ phase.After Cu doping,the NOx conversion rate of the CePO₄-H catalyst is enhanced,the active temperature window is broadened,and the NH₃-SCR catalytic denitration performance is significantly improved.The theoretical results show that both NH₃ and NO molecules can be adsorbed on the Ce and Cu active sites of Cu-doped CePO₄-H catalysts,and the adsorption configurations of both NH₃ and NO molecules on the Ce active sites exhibit higher stability.Compared with the undoped CePO₄-H catalyst,Cu doping significantly enhances the chemical adsorption capacity of the catalyst for NO,while the enhancement of its adsorption capacity for NH₃ is relatively modest.The adsorption of NH₃ on Cu active sites is physical adsorption,whereas the adsorption of NO is typical chemical adsorption.By regulating the electronic structure of the CePO₄-H catalyst surface,Cu doping increases the adsorption energy of reactant molecules,thereby significantly improving the catalytic activity of the NH₃-SCR reaction.This study provides experimental data and theoretical support for improving the NH₃-SCR denitration performance of CePO₄-H catalysts.

As a high-quality functional material with superior performance,Nd-Fe-B permanent magnets are widely used in fields such as aerospace,robotics,and renewable energy.However,their poor temperature stability limits their application in high-temperature environments.Currently,grain boundary diffusion using rare earth alloys or compounds has emerged as a promising technique to enhance the permanent magnetic properties of sintered Nd-Fe-B magnets.In this study,cost-effective TbF₃ was introduced into heavy rare earth-free sintered Nd-Fe-B magnets via grain boundary diffusion.The magnetic properties,microstructure,and elemental distribution of the magnets before and after diffusion were investigated.The results show that after TbF₃ grain boundary diffusion,the coercivity of the magnet increases from 16.81 kOe to 23.51 kOe,overcoming the inherent coercivity limitation of heavy rare earth-free sintered Nd-Fe-B.Meanwhile,the temperature coefficient of coercivity of the magnet is significantly improved,and its service temperature range is expanded from 20~100℃to 20~180℃.Electron probe and transmission electron microscopy analyses reveal that numerous Tb-enriched shell structures are formed in the diffused magnets,which effectively hinders the expansion of magnetic domains and enhances the thermal stability of the magnets.This study provides a scalable approach for optimizing the thermal stability of high-performance magnets,while alleviating the cost pressure associated with preparing high-performance Nd-Fe-B magnets via traditional alloy melting methods.

In order to improve the coercivity of sintered NdFeB magnets without adding heavy rare earth elements,this study adopted the grain boundary addition method to incorporate PrNdFeCuGaB alloy powders with different mass fractions(0,2%,4%,6%,and 8%)into NdFeB magnetic powders,and prepared sintered NdFeB magnets.The regulatory effects of PrNdFeCuGaB alloy addition content on the magnetic properties and microstructure of the magnets were systematically investigated.Combining the thermal activation theory,the intrinsic correlation between magnetic properties and microstructure was revealed.The results show that the matrix phase of the NdFeB magnets remains Nd₂Fe₁₄B regardless of the PrNdFeCu-GaB alloy addition content.The addition of PrNdFeCuGaB alloy optimizes the distribution of the RE-rich phases in the magnets,transforming them from an initially agglomerated morphology to a continuous striplike structure.These phases are distributed at the interfaces between adjacent matrix phase grains,resulting in more continuous and distinct grain boundaries.With the increase in PrNdFeCuGaB alloy addition content,the coercivity of the NdFeB magnets first increases and then decreases.The magnet achieves the optimal magnetic properties when the addition content of PrNdFeCuGaB alloy reaches 6%:B_r=13.85 kGs,H_cj=14.38 kOe,and(BH)_max=46.84 MGOe.The improvement in coercivity is attributed to two aspects:On the one hand,Pr atoms diffuse into the matrix phase to form a(Pr,Nd)₂Fe₁₄B shell layer,which enhances the interfacial anisotropy of the matrix phase grains.On the other hand,the formation of the(Pr,Nd)₆Fe₁₃Ga phase consumes the free Fe elements in the grain boundary regions,which allows the low-melting-point Ga and Cu elements to combine with Nd and Pr and migrate to the grain boundaries.This process forms a thin non-magnetic grain boundary layer between adjacent grains,which weakens the exchange coupling effect and strengthens the decoupling effect among the matrix phase grains.

The Mn-Ce/TiO₂ catalysts prepared by impregnation method were calcined at 300~500℃.XRD,BET,XPS,H₂-TPR,NH₃-TPD and denitration performance tests were conducted to investigate the effect of calcination temperature on the physical and chemical properties and denitration efficiency of Mn-Ce/TiO₂ denitration catalysts.The results show that the proper calcination temperature(400℃)is beneficial to increase the content of Mn⁴⁺,Ce³⁺and chemisorbed oxygen(O_α)of the catalyst,which can promote the denitration reaction.However,excessive calcination temperature(≥450℃)will lead to the increase of the particle size and the decrease of the dispersion of the active component MnO_x in the catalyst,and the decrease of the specific surface area of the catalyst.moreover,high calcination temperature also causes the decrease of the n(Mn⁴⁺)/n(Mn²⁺+Mn³⁺+Mn⁴⁺),n(Ce³⁺)/n(Ce³⁺+Ce⁴⁺),n(O_α)/n(O_α+O_β)and reducibility of the catalyst,which has an adverse effect on the denitration activity.The catalyst prepared at a calcination temperature of 400℃exhibits the best denitration activity within the flue gas temperature range of 120~270℃.

To clarify the influence of anisotropy induced by additive manufacturing on the damage behavior of titanium alloy components,Ti150 alloy specimens were fabricated using laser powder bed fusion technology in both vertical and horizontal build directions.The effects of build direction on the microstructure,tensile property anisotropy,and damage mechanism of the alloy were investigated.The results indicate that both vertically and horizontally built specimens form prior-βcolumnar grains along the build direction,with continuous or discontinuousα_GB phases precipitated at the prior-βgrain boundaries.Due to the collective influence of prior-βgrain boundary orientation andα_GB phase continuity on dislocation motion,the tensile properties of the vertically and horizontally built specimens exhibit anisotropy,primarily manifested as elongation differences.Quasi-in-situ tensile tests reveal that the continuousα_GB phase and prior-βgrain boundaries exhibit significant loading anisotropy,which provides favorable conditions for crack initiation and propagation,ultimately deteriorating the elongation of horizontally built specimens.

TA15 titanium alloy was selected as the experimental material,and the alloy was heat treated at different temperatures and cooled in different ways.The effects of heat treatment temperature and cooling methods on the microstructure and tensile properties of the alloy were studied.The results show that when the heat treatment temperature is 970℃(inα+βtwo-phase zone),the microstructure presents T-type texture,the alloy after water cooling or air cooling treatment is(α+β)two-phase structure,and there is a finer needle-likeαphase in the microstructure after water cooling.When the heat treatment temperature is 1000℃(inβzone),the microstructure shows R-type texture.This microstructure shows fine lamellar morphology after water cooling or air cooling treatment,and the primaryαphase disappears completely.α'phase is formed in the microstructure after water cooling treatment,whileαphase is formed in the microstructure after air cooling treatment.Regardless of the heat treatment temperature range,the strength of the alloy after water cooling is higher than that after air cooling.When the cooling methods are the same,compared with the(α+β)zone,the strength of the alloy is improved when the heat treatment temperature is inβzone,but the plasticity is significantly reduced.Regardless of the cooling method,the tensile fracture morphology of the alloy after heat treatment at the(α+β)zone temperature is composed of dimples.The tensile fracture after heat treatment at theβzone temperature is mainly coarse rock morphology,along with tear ridges and small shallow dimples.

The finishing temperature during hot rolling of beryllium bronze has significant impact on the microstructure and properties of beryllium copper alloy plates.Mechanical properties and microstructure of beryllium copper alloy plates with different hot rolling finishing temperatures subjected to identical subsequent cold rolling and heat treatment processes were analyzed by tensile property,hardness and electrical conductivity measurements,along with SEM and EDS.The corresponding variation trends were investigated.The results indicate that with increasing the hot rolling finishing temperature from 520℃to 620℃,the Vickers hardness,tensile strength,yield strength,elongation after fracture and elastic modulus of beryllium copper alloy plates gradually increase,while the electrical conductivity decreases.This is primarily due to the more severe grain boundary reactions and highβ-phase content in the beryllium copper alloy plates at lower hot rolling finishing temperature,leading to the deterioration of alloy properties.

With the rapid development and industrial upgrading of the manufacturing industry,market demands for high efficiency,high quality and low cost of solid carbide cutting tools are continuously increasing.The performance improvement of ultrafine-grained cemented carbide rods,as the matrix material for solid carbide cutting tools,has attracted extensive attention.In this paper,based on the traditional liquidphase sintering process,ultrafine-grained WC-12%Co cemented carbide rods were designed and prepared via a two-step sintering process using WC as the matrix,Co as the binder phase,and Cr₃C₂ and VC as inhibitors.Through comparative experiments,the effects of the two-step sintering process and the traditional liquid-phase sintering process on the physical and mechanical properties,microstructure,and cutting performance of the alloy rods were systematically investigated.The difference between the two-step sintering process and the traditional liquid-phase sintering process lies in the special high-temperature stage procedure of“heating to sintering temperature-high-pressure controlled-speed cooling to eutectic temperaturereheating to sintering temperature for heat preservation”.This process optimization enables more sufficient dissolution and precipitation of WC,effectively improving the WC/Co interface bonding state and grain size distribution.Consequently,the alloy achieves a synergistic enhancement in fracture toughness and bending strength,with a significant improvement in the stability of bending strength.The solid carbide end mill made from the cemented carbide matrix prepared by the two-step sintering process exhibits significantly improved tool life when machining NAK80 plastic mold steel,with reduced micro-chipping failure and enhanced life stability.This study provides a process reference for the preparation of high-performance ultrafine-grained cemented carbides.