Phase-Field Simulation of Sintering Process:A Review

Sintering,a well-established technique in powder metallurgy,plays a critical role in the processing of high melting point materials.A comprehensive understanding of structural changes during the sintering process is essential for effective product assessment.The phase-field method stands out for its unique ability to simulate these structural transformations.Despite its widespread application,there is a notable absence of literature reviews focused on its usage in sintering simulations.Therefore,this paper addresses this gap by reviewing the latest advancements in phase-field sintering models,covering approaches based on energy,grand potential,and entropy increase.The characteristics of various models are extensively discussed,with a specific emphasis on energy-based models incorporating considerations such as interface energy anisotropy,tensor-form diffusion mechanisms,and various forms of rigid particle motion during sintering.Furthermore,the paper offers a concise summary of phase-field sintering models that integrate with other physical fields,including stress/strain fields,viscous flow,temperature field,and external electric fields.In conclusion,the paper provides a succinct overview of the entire content and delineates potential avenues for future research.

Spark Plasma Sintering of Boron Carbide Using Ti_(3)SiC_(2) as a Sintering Additive

Boron carbide has unique properties for wide application possibilities;however,poor sinterability limits its applications.One approach to overcome this limitation is the addition of secondary phases into boron carbide.Boron carbide based composite ceramics are produced by the direct addition of secondary phases into the structure or via reactive sintering using a sintering additive.The present study investigated the effect of Ti_(3)SiC_(2) addition to boron carbide by reactive spark plasma sintering in the range of 1700-1900℃.Ti_(3)SiC_(2) phase decomposed at high temperatures and reacted with B4C to form secondary phases of TiB2 and SiC.The results demonstrated that the increase of Ti_(3)SiC_(2) addition(up to 15 vol%)effectively promoted the densification of B4C and yielded higher hardness.However,as the amount of Ti_(3)SiC_(2) increased further,the formation of microstructural inhomogeneity and agglomeration of secondary phases caused a decrease in hardness.

Effect of Sintering Temperature on the Microstructure and Mechanical Properties of Nanocrystalline Cemented Carbide

WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.

Spark Plasma Sintering of Mg-based Alloys:Microstructure,Mechanical Properties,Corrosion Behavior,and Tribological Performance

Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the concept of Joule heating.Compared to traditional and additive manufacturing(AM)techniques,SPS gives unique control of the structural and microstructural features of Mg components.By doing so,their mechanical,tribological,and corrosion properties can be tailored.Although great advancements in this field have been made,these pieces of knowledge are scattered and have not been contextualized into a single work.The motivation of this work is to address this scientific gap and to provide a groundwork for understanding the basics of SPS manufacturing for Mg.To do so,the existing body of SPS Mg literature was first surveyed,with a focus on their structural formation and degradation mechanisms.It was found that successful Mg SPS fabrication highly depended on the processing temperature,particle size,and particle crystallinity.The addition of metal and ceramic composites also affected their microstructural features due to the Zener pinning effect.In degradative environments,their performance depends on their structural features and whether they have secondary phased composites.In industrial applications,SPS'd Mg was found to have great potential in biomedical,hydrogen storage,battery,automotive,and recycling sectors.The prospects to advance the field include using Mg as a doping agent for crystallite size refinement and using bulk metallic Mg-based glass powders for amorphous SPS components.Despite these findings,the interactions of multi-composites on the processing-structure-property relationships of SPS Mg is not well understood.In total,this work will provide a useful direction in the SPS field and serve as a milestone for future Mg-based SPS manufacturing.

Fabrication of YAG:Ce^(3+) and YAG:Ce^(3+),Sc^(3+) Phosphors by Spark Plasma Sintering Technique

In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.

Spark plasma sintering of tungsten-based WTaVCr refractory high entropy alloys for nuclear fusion applications

W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6through a combined analysis of X-ray diffraction (XRD),energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro-and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.

Anti-sintering behavior and combustion process of aluminum nano particles coated with PTFE:A molecular dynamics study

The characteristic of easy sintering of aluminum nanoparticle(ANP)limits its application in solid propellants.Coating ANP with fluoropolymer could effectively improve its combustion performance.To find out how the coating layer inhibits sintering and promotes complete combustion of particles from an atomic view,a comparative study has been done for bare ANP and PTFE coated ANP by using reactive molecular dynamics simulations.The sintering process is quantified by shrinkage ratio and gyration radius.Our results show that,at the same heating rate and combustion temperatures,bare ANPs are sintered together after the temperature exceeds the melting point of aluminum but the decomposition of PTFE coating layer pushes particles away and increases reaction surface area by producing small Al-F clusters.The sintering of ANPs which are heated in PTFE is alleviated compared with particles heated in oxygen,but particles still sinter together due to the lack of intimate contact between PTFE and alumina surface.The effect of temperature on the combustion of PTFE coated ANPs is also studied from 1000 to3500 K.The number density analysis shows the particles will not be sintered at any temperature.Aluminum fluoride prefers diffusing to the external space and the remained particles are mainly composed of Al,C and O.Fast ignition simulations are performed by adopting micro canonical ensemble.With the expansion of aluminum core and the melting of alumina shell,bare ANPs are sintered into a liquid particle directly.For PTFE coated ANPs,the volatilization of gaseous aluminum fluoride products continually endows particles opposite momentum.

Influences of oxide content and sintering temperature on microstructures and mechanical properties of intragranular-oxide strengthened iron alloys prepared by spark plasma sintering

How to increase strength without sacrificing ductility has been developed as a key goal in the manufacture of high-performance metals or alloys. Herein, the double-nanophase intragranular yttrium oxide dispersion strengthened iron alloy with high strength and appreciable ductility was fabricated by solution combustion route and subsequent spark plasma sintering, and the influences of yttrium oxide content and sintering temperature on microstructures and mechanical properties were investigated. The results show at the same sintering temperature,with the increase of yttrium oxide content, the relative density of the sintered alloy decreases and the strength increases. For Fe–2wt%Y_(2)O_(3)alloy, as the sintering temperature increases gradually, the compressive strength decreases, while the strain-to-failure increases. The Fe–2wt%Y_(2)O_(3)alloy with 15.5 nm Y_(2)O_(3)particles uniformly distributed into the 147.5 nm iron grain interior sintered at 650℃ presents a high ultimate compressive strength of 1.86 GPa and large strain-to-failure of 29%. The grain boundary strengthening and intragranular second-phase particle dispersion strengthening are the main dominant mechanisms to enhance the mechanical properties of the alloy.

Evaluation of the Air Leakage Flowrate in Sintering Processes

Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena of various types.As experimental measurements are relatively difficult and often scarcely reliable,here a theoretical model based on typicalfluid-dynamic concepts and relationships is elaborated.Through the analysis of two extreme cases,namely,those in which leakage is due to a small hole or a full rupture,a generalized hole-bed mod-el is introduced,which for thefirst time also includes a complete bed permeability equation and can deal with different leakage position conditions.The results show that the model can evaluate the influence of leakage on the system at one time and be used to calculate theflowrate and pressure drop.Notably,the obtained results are within a 15%deviation with respect to available experiment values,used for comparison.

Effect of sintering temperature on microstructure and properties of 3D printing polysilazane reinforced Al_(2)O_(3)core

Ceramic cores are the key intermediate components of hollow blades for aero-engine.Conventional processes,such as hot-press molding and gel film casting,face difficulties in fabricating complex-structured ceramic cores due to the complexity of moulds and long process cycles.Stereolithography 3D printing provides a new idea for the fabrication of complex-structured ceramic cores.The effect of sintering temperature on open porosity,bulk density,weight loss rate,shrinkage rate,flexural strength and microstructure of the Al_(2)O_(3)-based ceramic core doped with 10vol.%polysilazane(PSZ)was studied.The sintering mechanism of PSZ-reinforced ceramic cores was analyzed.Results show that the optimum sintering temperature of PSZ-reinforced ceramic cores is 1,450°C.At this temperature,the open porosity of the ceramic core is 36.60%,bulk density is 2.33 g·cm^(-3),weight loss rate is 22.11%,shrinkage rate along the X,Y,Z directions is 5.72%,5.01%,9.61%,respectively;the flexural strength is 28.794 MPa at 25°C and 13.649 MPa at 1,500°C.Properties of 3D printing PSZ-reinforced ceramic cores can meet the casting requirement of superalloy hollow blades,which is expected to promote the industrial application of 3D printing complex structure ceramic cores.

Preparation of coated sand for selective laser sintering and optimization of baking process of sand moulds

A cold method was used to prepare coated sand for application in the selective laser sintering(SLS)process.Tensile strength,loss on ignition,gas evolution,and accuracy of the SLS samples were tested and analyzed,and the baking process was thoroughly investigated.Compared with coated sand prepared by the hot method,the cold method yields a more uniform and complete resin film on the sand's surface,resulting in enhanced tensile strength and accuracy.Additionally,the cold method requires a lower binder content to meet the same strength requirements,thereby minimizing gas evolution,reducing porosity defects,and ultimately improving casting quality.The coated sand samples prepared through the cold method exhibit superior accuracy,with a size error of within±0.4 mm.In contrast,the coated sand samples prepared by the hot method display a lower accuracy,with an average negative error of 2.1993 mm.The highest tensile strength could be attained by controlling the baking temperature within a suitable range(180-190°C),which can effectively reduce the generation of gas,thus contributing to improved overall performance.

Effect of steam spraying on a sintering bed on sinter quality and the emission of flue gas pollutants

The technology for spraying a sintering bed and thus improving sinter quality indicators while reducing the emission of flue gas pollutants has recently become an important research topic.The impacts on sinter quality and emissions when spraying the sintering surface with different amounts and flow rates of steam were investigated in this study.The sinter quality indicators were most effectively improved by spraying 180 g of steam flow continuously at a rate of 0.02 m^(3)/min for 15 min after ignition for 8 min.The optimal effect on emission reduction was obtained by spraying 90 g of steam flow continuously at a rate of 0.01 m^(3)/min for 15 min after ignition for 8 min.

LiCoO_(2) sintering aid towards cathode-interface-enhanced garnet electrolytes

Garnet-type Li_7La_(3)Zr_(2)O_(12)(LLZO) has high ionic conductivity and good compatibility with lithium metal.High-temperature processing has been proven an effective method to decrease the interface resistance of cathodeILLZO.However,its application is still hindered by the interlayer co-diffusion with the cathode and high sintering temperature(>1200℃).In this work,a new garnet-type composite solid-state electrolyte(SSE) Li_(6.54)La_(2.96)Ba_(0.04)Zr_(1.5)Nb_(0.5)O_(12)-LiCoO_(2)(LLBZNO-LCO) is firstly proposed to improve the chemical stability and electrochemical properties of garnet with high-temperature processing.Small doses of LCO(3%) can significantly decrease the LCOISSE interface resistance from 121.2 to 10.1 Ω cm~2,while the sintering temperature of garnet-type LLBZNO decreases from 1230 to 1000℃.The all-solid-state battery based on the sintered LLBZNO-LCO SSE exhibits excellent cycling stability.Our approach achieves an enhanced LCOISSE interface and an improved sintering activity of garnet SSE,which provides a new strategy for optimizing the comprehensive performance of garnet SSE.

Sintering Densification of Boron Carbide Materials and Their Research Progress

Boron carbide(B_(4)C)has excellent high-temperature oxidation resistance,high hardness,low relative density,high melting point and excellent abrasive resistance,which is widely used in fields such as refractories,wear-resistant materials and lightweight protective materials.The research progress and application of B_(4)C materials in China and overseas in recent years were summarized.The influences of sintering processes(pressureless sintering,hot-pressing sintering,hot isostatic pressing sintering,spark plasma sintering and microwave sintering)and sintering additives(simple substances,oxides and carbides)on the B_(4)C densification were analyzed.The development of B_(4)C materials was prospected.

Impact Analysis of Microscopic Defect Types on the Macroscopic Crack Propagation in Sintered Silver Nanoparticles

Sintered silver nanoparticles(AgNPs)arewidely used in high-power electronics due to their exceptional properties.However,the material reliability is significantly affected by various microscopic defects.In this work,the three primary micro-defect types at potential stress concentrations in sintered AgNPs are identified,categorized,and quantified.Molecular dynamics(MD)simulations are employed to observe the failure evolution of different microscopic defects.The dominant mechanisms responsible for this evolution are dislocation nucleation and dislocation motion.At the same time,this paper clarifies the quantitative relationship between the tensile strain amount and the failure mechanism transitions of the three defect types by defining key strain points.The impact of defect types on the failure process is also discussed.Furthermore,traction-separation curves extracted from microscopic defect evolutions serve as a bridge to connect the macro-scale model.The validity of the crack propagation model is confirmed through tensile tests.Finally,we thoroughly analyze how micro-defect types influence macro-crack propagation and attempt to find supporting evidence from the MD model.Our findings provide a multi-perspective reference for the reliability analysis of sintered AgNPs.

APPLICATION OF HOT-PRESS SINTERING TECHNIQUE TO EXPLOSIVE CHARGE LINER OF PETROLEUM PERFORATION BULLET

介绍了一种制备石油射孔弹的药形罩的新方法，采用粉末冶金技术，热压烧结工艺制备石油射孔弹的药形罩，并对药形罩的烧结工艺进行了研究。实验结果表明，采用该工艺制备的石油射孔弹药形罩可以满足要求。

STUDIES ON SINTERING TECHNOLOGY OF HAMMERS OF FOOD HAMMER MILL

提出了粉碎机锤片的烧结新工艺，并且系统研究了烧结配方、工艺参数。通过单因素试验和正交试验获得最佳参数。实验结果为锤片的进一步应用提供了理论指导和实验数据。

Simultaneous desulfurization and denitrification of sintering flue gas via composite absorbent

Experiments on simultaneous absorption of SO_2 and NO_X from sintering flue gas via a composite absorbent NaClO_2/NaClO were carried out. The effects of various operating parameters such as NaClO_2 concentration(ms), NaClO concentration(mp), molar ratio of NaClO_2/NaClO(M), solution temperature(TR), initial solution pH, gas flow(Vg) and inlet concentration of SO_2(CS) and NO(CN) on the removal efficiencies of SO_2 and NO were discussed. The optimal experimental conditions were determined to be initial solution pH = 6, TR=55 °C and M = 1.3 under which the average efficiencies of desulfurization and denitrification could reach99.7% and 90.8%, respectively. Moreover, according to the analysis of reaction products, it was found that adding NaClO to NaClO_2 aqueous solution is favorable for the generation of ClO_2 and Cl_2 which have significant effect on desulfurization and denitrification. Finally, engineering experiments were performed and obtained good results demonstrating that this method is practicable and promising.

Multi-Objective Optimization and Analysis Model of Sintering Process Based on BP Neural Network

A multi-objective optimization and analysis model of the sintering process based on BP neural network is presented. Genetic algorithms are combined to simplify the BP neural network, which can reduce the learning time and increase the forecasting accuracy of the network model. This model has been experimented in the sintering process, and the production cost, the energy consumption, the quality （revolving intensity）, and the output are considered at the same time. Moreover, the relation between some factors and the multi-objectives has been analyzed, and the results are consistent with the process. Different objectives are emphasized at different practical periods, and this can provide a theoretical basis for the manager.

Effect of particle size on the microstructure and thermal conductivity of Al/diamond composites prepared by spark plasma sintering

Spark plasma sintering （SPS） was used to fabricate Al/diamond composites. The influence of diamond particle size on the microstructure and thermal conductivity （TC） of composites was investigated by combining experimental results with model prediction. The results show that both composites with 40 pan particles and 70 μm particles exhibit high density and good TC, and the composite with 70 μm particles indicates an excellent TC of 325 W.m^-1.K^-1. Their TCs lay between the theoretical estimated bounds. In contrast, the composite with 100 lain particles demonstrates low density as well as poor TC due to its high porosity and weak interfacial bonding. Its TC is even considerably less than the lower bound of the predicted value. Using larger diamond particles can further enhance thermal conductive performance only based on the premise that highly dense composites of strong interfacial bonding can be obtained.