On the basis of Al-V-B grain refining agent,rare earth element La was added,and Al-5V-3B-0.5La intermediate alloy was prepared by sintering method.The size,distribution,and morphology of nucleation particles in the re...On the basis of Al-V-B grain refining agent,rare earth element La was added,and Al-5V-3B-0.5La intermediate alloy was prepared by sintering method.The size,distribution,and morphology of nucleation particles in the refining agent at different sintering temperatures and the refining effect on A356 alloy were studied.The experimental results show that with the increase of sintering temperature,the addition of La element reduces the particle size of nucleated particles in the refining agent,makes the distribution more uniform,and has a good grain refinement effect on A356 alloy,with a significant reduction in grain size to around 184.62μm.It provides reference for the development of high-quality grain refining agents.展开更多
It is a practically significant issue to refine and modify industrial Al-Si casting alloy to improve its properties.In the present study,a novel refiner Al-3Ti-4.35La alloy,prepared by a melt-reaction method,was used,...It is a practically significant issue to refine and modify industrial Al-Si casting alloy to improve its properties.In the present study,a novel refiner Al-3Ti-4.35La alloy,prepared by a melt-reaction method,was used,combined with Sr to refine the as-cast A356 alloy.Their effects on the as-cast microstructures and mechanical properties of A356 alloy were investigated.The results indicate that the combined addition of Al-3Ti-4.35La intermediate alloy and Sr can improve the microstructure and enhance the mechanical properties of A356 alloy.After adding 0.3wt.%Al-3Ti-4.35La and 0.03wt.%Sr to the as-cast A356 alloy,the average grain size ofα-Al decreases from 693.47μm to 264.13μm(a decrease of 61.91%),the secondary dendrite arm spacing(SDAS)is decreased by 47.8%from 32.09μm to 16.75μm,and the eutectic Si is transformed from an acicular structure to short rods and a granular structure.The ultimate tensile strength(UTS)and elongation(EL)of the as-cast A356 alloy modified by Al-3Ti-4.35La and Sr reach 216.3 MPa and 10.6%,which are enhanced by 29.54%and 134.66%compared with the unmodified alloy,respectively.The fracture mode is transformed from transgranular fracture to intergranular fracture,and the ductile toughness of the alloy is improved.After adding the Al-3Ti-4.35La and Sr,the undercooling for the nucleation ofα-Al and eutectic Si increases,leading to an accelerated nucleation rate and an increased number of nuclei,which shortens the duration of the eutectic reaction and consequently inhibits grain growth.展开更多
Grain refinement is a satisfying method to enhance the comprehensive performance of Mg alloys,and using grain refiners to improve the quality of Mg castings has become a common practice in the current casting industry...Grain refinement is a satisfying method to enhance the comprehensive performance of Mg alloys,and using grain refiners to improve the quality of Mg castings has become a common practice in the current casting industry.In this study,the effects of Al-CeO_(2)-Mg grain refiner addition on microstructure,cast fluidity,and mechanical properties of AZ91 alloy were systemically investigated by OM,SEM,DSC,TEM,sand Archimedean spiral mold fluidity test,and tensile test.The results show that the Al-CeO_(2)-Mg grain refiner has a remarkable effect on as-cast AZ91 alloy including notable grain refinement,enhancement of cast fluidity,and improvement of tensile properties.The average grain size of AZ91 alloy is refined by 63%with 1.0wt.%Al-CeO_(2)-Mg grain refiner.Meanwhile,the casting flow length of the as-cast AZ91 alloy is increased from 332 mm to 440 mm.The improvement of cast fluidity is attributed to the decreased liquidus temperature,shortening of solid-liquid two-phase temperature range,and refinement of microstructure.展开更多
The mechanical properties of as-cast metallic materials depend strongly on the size and shape of grains,which are critical microstructural parameters dictated by the interplay of nucleation and growth of crys-talline ...The mechanical properties of as-cast metallic materials depend strongly on the size and shape of grains,which are critical microstructural parameters dictated by the interplay of nucleation and growth of crys-talline solids during solidification.In our experiments,the microstructure transition from coarse colum-nar crystals into fine equiaxed crystals for dilute Al-Mn-Si alloys was achieved by using sub-rapid so-lidification with the addition of Al-5Ti-1B grain refiner.The average grain size of Al alloy was reduced from a millimeter size to 73μm.Through temperature gradient calculation,we found that the acqui-sition of fine equiaxed crystals could be attributed to the existence of a high number density of TiB2,acting as effective nucleation sites with an increase in total undercooling.Furthermore,the curvature su-percooling,constitutional undercooling,thermal undercooling,and kinetic undercooling during sub-rapid solidification were quantitatively determined for given solidification rates.Our results showed that con-stitutional undercooling,rather than thermal undercooling,was primarily responsible for the formation of fine equiaxed grains,with the assistance of Al-5Ti-1B grain refiner.This work provides a new insight into the grain refining mechanism under sub-rapid solidification.展开更多
Al-Si alloys have excellent corrosion resistance,low thermal expansion coefficient,and high strength-to-weight ratio,which make them widely used in structural components in the automotive and aerospace industries[1,2]...Al-Si alloys have excellent corrosion resistance,low thermal expansion coefficient,and high strength-to-weight ratio,which make them widely used in structural components in the automotive and aerospace industries[1,2].However,the coarseα-Al dendrites result in poor mechanical properties[3,4],and the widely used Al-5Ti-B(all compositions are in wt.%unless otherwise specified)refiner fails in as-cast aluminum alloys with high silicon content(≥5 wt.%)due to the Si-poisoning effect[5,6].Fortunately,in order to overcome Si-poisoning,a series of refiners have been developed.Al-B refiner is effective for refining aluminum alloys with high silicon content,but it is easy to be poisoned by Ti/Zr[7,8].Al-Nb-B[9–11]and Al-V-B[12]refiners have a certain ability to overcome Si-poisoning,while the nucleating particles have a large density and are easy to agglomerate and settle,leading to the grain refinement fading phenomenon.Al-Ti-C-B refiner realizes the anti-Si/Zrpoisoning ofα-Al grain refinement based on the evolving effect of a doped TCB complex[13,14].Al-Ti-Nb-B refiner prepared with Nb partially substituted Ti can improve the refinement level of Al-10Si alloy to 109–125μm[15,16].However,the existing preparation method of the refiner uses pure Nb powder as raw material,resulting in high preparation costs,which limits its application in industry to a certain extent.展开更多
To investigate the effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg （A357） alloy, some novel Al-7.0Si-0.55Mg alloys added with different amount of Al-STi-1B-RE grain...To investigate the effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg （A357） alloy, some novel Al-7.0Si-0.55Mg alloys added with different amount of Al-STi-1B-RE grain refiner with different RE composition were prepared by vacuum-melting. The microstructure and fracture behavior of the AI-7.0Si-0.55Mg alloys with the grain refiners were observed by X-ray diffraction （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM）, and the mechanical properties of the alloys were tested in mechanical testing machine at room temperature. The observation of AI-Ti-B-RE morphology and internal structure of the particles reveals that it exhibits a TiAl3/Ti2Al20RE core-shell structure via heterogeneous TiB2 nuclei. The tensile strength of Al-7.0Si-0.55Mg alloys with Al-5Ti-1B-3.0RE grain refiner reaches the peak value at the same addition （0.2%） of grain refiner.展开更多
A novel type nano TiN/Ti composite grain refiner （TiN/Ti refiner） was prepared by high energy ball milling, and its effect on as-cast and hot-working microstructure of commercial purity aluminum （pure Al） was inve...A novel type nano TiN/Ti composite grain refiner （TiN/Ti refiner） was prepared by high energy ball milling, and its effect on as-cast and hot-working microstructure of commercial purity aluminum （pure Al） was investigated. The results show that TiN/Ti refiner exhibits excellent grain refining performances on pure Al. With an addition of 0.2% TiN/Ti refiner, the average grain size of pure Al decreases to 82 μm, which is smaller than that of pure Ti and Al 5Ti 1B master alloy as refiners. The microstructure of weld joint of pure Al with 0.1% TiN/Ti refiner is fine equiaxed grains and the hardness of weld joint is higher than that of the base metal. For pure Al with 40% cold deformation and recrystallization at 250 °C for 1.0 h, the grains of the sample added 0.1% Ti powder have an obvious grain growth behavior. In contrast, oriented grains caused by deformation have been eliminated, and there is no obvious grain growth in pure Al refined with 0.1% TiN/Ti refiner, indicating that nano TiN in the refiner inhibits the growth of grain during recrystallization.展开更多
Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refi...Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refiner plates is of significance to the wood industry. It may affect refining quality, production efficiency, and power consumption. In this paper, the abrasion resistance of the refiner plate made of different materials, the stainless steels and high chromium cast irons, were tested and compared. The results showed that abrasion resistance of refiner plate made of high chromium cast irons was better than that of the stainless steel materials. Although the two kinds of materials have the same compositions, their abrasion resistances have ap-parent difference. The main reason is that the material microstructures have very important effects on their performance. The refiner plates made of developed high chromium cast irons don抰 demand the complex heat treatment. This can simplify the producing process, save the cost of production, decrease labor strength, and increase the production efficiency.展开更多
Al-Ti-C grain refiner was prepared by SHS （self-propagating high-temperature synthesis ）-melting technique. The effect of La on the microstructures of grain refiner was studied by OM, TEM, SEM, XRD, and EDS. The exp...Al-Ti-C grain refiner was prepared by SHS （self-propagating high-temperature synthesis ）-melting technique. The effect of La on the microstructures of grain refiner was studied by OM, TEM, SEM, XRD, and EDS. The experimental results indicate that La can improve the wettability between liquid aluminum and graphite ; the addition of La results in dispersive distribution of TiAl3 and TiC particles in the matrix. An excellent grain refining performance of Al-Ti-C grain refiner on commercially pure Al was obtained.展开更多
To investigate the effect of rare earth on size and distribution of TiB2 phase in aluminum alloy refiner,Al-5Ti-1B-RE master alloy was fabricated,and its microstructure and phase constitutions were investigated by the...To investigate the effect of rare earth on size and distribution of TiB2 phase in aluminum alloy refiner,Al-5Ti-1B-RE master alloy was fabricated,and its microstructure and phase constitutions were investigated by the combination of first principles calculations and experimental investigation.The calculated results reveal that Ce has the most effective modification ability due to the most positive adsorption energy and the largest charge transfer value compared with other rare earth elements.Results of experimental investigation indicate that the addition of rare earth in the Al-5Ti-1B alloys can greatly refine the particle size of TiB2,improve the distribution of particles and lead to better refinement effect than that of the Al-5Ti-1B alloys without rare earth.Moreover,Ce has the best optimization effect,which agrees well with the calculated results.展开更多
An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS...An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.展开更多
1 INTRODUCTIONWood chip refining is the most critical step in mechanical pulping.Commercical experi-ences have been gained for years.Modelling and control of chip refiners,however,pose a challenge mainly because of th...1 INTRODUCTIONWood chip refining is the most critical step in mechanical pulping.Commercical experi-ences have been gained for years.Modelling and control of chip refiners,however,pose a challenge mainly because of the stochastic nature of the process.Some attemptshave been made to employ factor analysis technique[1]in the modelling andsimulating of refiner operation[2,3].Strand[2]used common factors as links betweenintrinsic fibre properties and pulp quality.He believed that a qualitative concept onthe physical nature of these common factors could be arrived at,and thus would helpto understand what refining variables need to be controlled or adjusted in order to im-prove pulp quality.However,the linear model used in factor analysis is based on theassumption that the interactions among the system variables are linear,which,ofcourse,is not true in practice.展开更多
A novel grain refiner composed of nickel, tungsten and yttria was prepared by the powder metallurgy way. The mierostructure of the refiner alloy was studied by optical microscope （OM）, scanning electron microscope ...A novel grain refiner composed of nickel, tungsten and yttria was prepared by the powder metallurgy way. The mierostructure of the refiner alloy was studied by optical microscope （OM）, scanning electron microscope （SEM） and energy dispersive spectroscopy （EDS）. The refinement process was simplized. It was shown that the alloy grains could be refined by addition of the refiners apparently even at high pouring temperature. The average grain size of the refiner free alloy was 4 mm, and 0.4 mm for the refined alloy. The fine-grain superalloy has excellent mechanical properties at intermediate temperature. The refinement mechanism was discussed.展开更多
It was discussed how refiner plate is produced by a new process, such as three dimension making die with computer technology, shell molding, optimizing the alloy and controlling shakeout time with computer. Results co...It was discussed how refiner plate is produced by a new process, such as three dimension making die with computer technology, shell molding, optimizing the alloy and controlling shakeout time with computer. Results confirmed that lead-time was decreased and product customization was improved in making die by using computer technology. At the same time, precision molding can decrease the reject ratio of refiner plates, and optimizing the alloy and shakeout time can eliminate the need for heat treatment. The new fabricating process showed several advantages over the traditional process in increasing toughness, better casting precision, elimination of the annealing treatment stage and raising production efficiency.展开更多
The Al-5Cu alloys were prepared by different treatment methods,including adding a refiner Al-5Ti-1B,exerting a rotating magnetic field(RMF),and compound treatment of both refiner and RMF.The effects of treatment metho...The Al-5Cu alloys were prepared by different treatment methods,including adding a refiner Al-5Ti-1B,exerting a rotating magnetic field(RMF),and compound treatment of both refiner and RMF.The effects of treatment methods on the microstructure,properties,and solid solubility of the Al-5Cu alloy were investigated.The optimal magnetic field parameters and addition amount of refiner were confirmed by experiment.Results show that either RMF or adding refiner Al-5Ti-1B alone can refine the grain size,and the refining effect can be further improved by a compound refining treatment with optimized magnetic field parameters(120 A current and 8 Hz frequency) and 1.0wt.% Al-5Ti-1B refiner(RMF*+Al-5Ti-1B*).The average grain size is decreased to 68.1 μm,which is 60.8%,21.1%,and 83.5% lower than that of the alloy treated by the optimized rotating magnetic field,the Al-5Ti-1B refiner,and the alloy without any treatment,respectively.The tensile strength and elongation of the alloy reach 232.5 MPa and 18.6%,respectively,which are obviously higher than those of the alloys treated by rotating magnetic field,Al-5Ti-1B refiner,and the alloy without any treatment,respectively.Additionally,the solid solubility of the alloy is also obviously improved compared to the alloys treated by other methods.展开更多
Straight-and curved-bar refining plates are two important types of plates commonly used in disc refiners in the papermaking industry.Theoretically,the curved-bar refining plate has a relatively uniform bar interaction...Straight-and curved-bar refining plates are two important types of plates commonly used in disc refiners in the papermaking industry.Theoretically,the curved-bar refining plate has a relatively uniform bar interaction angle,which indicates uniform refining effects.The bar angle of the curved bar was proposed and two typical curved-bar plates,the three-stage radial curved-bar plate and isometric curved-bar plate,were designed in this paper.The arc equations of the curved-bar center line and curved-bar edges were established and finally,the specific edge load(SEL)of the curved-bar plate was derived.The determination of bar parameters was discussed,which provides a theoretical basis for the design of curved-bar plates.展开更多
Disc refiner is a critical equipment in the pulping and papermaking industry, pulp is refined in the refining zone, and different bar structures of refining disc constitute the different refining zones. With the use o...Disc refiner is a critical equipment in the pulping and papermaking industry, pulp is refined in the refining zone, and different bar structures of refining disc constitute the different refining zones. With the use of the 3D modeling software SOLIDWORKS, five different refining discs that are commonly used in low consistency pulping, were built. The five refining discs were simulated and analyzed using the Computational Fluid Dynamics(CFD)software. The distribution of pulp velocity and surface shear stress, which is displayed between the bar and groove structures, can indirectly show the stress conditions on the refining discs. This paper provides a theoretical basis for research on the bar and groove failure of the refining discs.展开更多
An electrostrictive uniaxial ultrasonic levitation reaction system was designed to perform TiC synthesis reaction by suspending graphite powder in Al-3Ti melt and an Al-3Ti-0.15C grain refiner alloy was obtained. The ...An electrostrictive uniaxial ultrasonic levitation reaction system was designed to perform TiC synthesis reaction by suspending graphite powder in Al-3Ti melt and an Al-3Ti-0.15C grain refiner alloy was obtained. The results show that sound pressure node in which graphite suspends is formed in the melt between radiation block and reflecting board by ultrasonic and TiAl3 particles congregate around C powder. Meanwhile, due to ultrasonic cavitation, dissolved TiAl3 provides better surface condition for the synthesis reaction of TiC. The reaction route is that C and dissolved Ti react to form TiC. Ultrasonic cavitation has a thermal activation effect on TiC particles and Al-3Ti-0.15C refiner has excellent microstructural refining effect on α-Al.展开更多
Power consumption is the energy source of the impact on fibers or pulp during low-consistency(LC)pulp refining,and the strength of refining affects refining quality and efficiency.The pulp properties,operating paramet...Power consumption is the energy source of the impact on fibers or pulp during low-consistency(LC)pulp refining,and the strength of refining affects refining quality and efficiency.The pulp properties,operating parameters,and bar parameters of the refiner plates are important parameters affecting refining efficiency,which can be defined as the ratio of net to total refining power.In this study,LC refining trials for pulps with different consistencies and fiber lengths were conducted using five isometric straightbar plates with different bar angles to explore the influences of the plate bar angle and pulp properties on the no-load power,impact capacity on fibers and refining efficiency.It was found that the no-load power of the LC refining process decreased with an increase in the plate bar angle while increased when pulp with higher consistency was refined under the same refining conditions.However,the effect of pulp consistency on the no-load power can be neglected when refining is conducted using plates with larger bar angles.Meanwhile,a critical bar angle for straight-bar plates in LC refining may exist,which has the strongest impact on the pulp and highest refining efficiency under the same refining conditions.In addition,the impact capacity of the plate on the pulp and refining efficiency in LC refining can be enhanced by appropriately increasing the pulp consistency and average fiber length when the bar angle of the refiner plate with a sector angle of 40°is less than 30°.Therefore,the efficiency and power consumption of the LC refining process can be adjusted by optimizing the pulp consistency and bar parameters of the refining plates.展开更多
Currently ＂The Crude Formulation Technique＂ developed by the SINOPEC Research Institute of Petroleum Processing（RIPP） has passed the technical review sponsored by the Sinopec Corp.This technique by means of adopti...Currently ＂The Crude Formulation Technique＂ developed by the SINOPEC Research Institute of Petroleum Processing（RIPP） has passed the technical review sponsored by the Sinopec Corp.This technique by means of adopting the advanced algorithm on the basis of the crude assay data bank and the large crude spectroscopic database can intelligently blend together different kinds of crude oils to obtain multiple crude formulations, the quality of which is quite close to the target crude in a bid to provide technical support to the refining enterprises in the area of crude procurement and sustained property stabilization of crude oils pro-cessed thereby.展开更多
基金Funded by the Science and Technology Project of State Grid Shanghai Municipal Electric Power Company(No.5209A6240003)the 2024 Shanxi Provincial Major Science and Technology Special Project(No.202401050201003)。
文摘On the basis of Al-V-B grain refining agent,rare earth element La was added,and Al-5V-3B-0.5La intermediate alloy was prepared by sintering method.The size,distribution,and morphology of nucleation particles in the refining agent at different sintering temperatures and the refining effect on A356 alloy were studied.The experimental results show that with the increase of sintering temperature,the addition of La element reduces the particle size of nucleated particles in the refining agent,makes the distribution more uniform,and has a good grain refinement effect on A356 alloy,with a significant reduction in grain size to around 184.62μm.It provides reference for the development of high-quality grain refining agents.
基金financially supported by the National Natural Science Foundation of China(Grant No.52161006)an Industrial Support Plan Project of Gansu Provincial Department of Education(2021CYZC-23)+2 种基金the Gansu Key Research and Development Program(21YF5GD183)the Jiayuguan Science and Technology Planning Project(21-10)the China Postdoctoral Science Foundation Project(2019M653896XB)。
文摘It is a practically significant issue to refine and modify industrial Al-Si casting alloy to improve its properties.In the present study,a novel refiner Al-3Ti-4.35La alloy,prepared by a melt-reaction method,was used,combined with Sr to refine the as-cast A356 alloy.Their effects on the as-cast microstructures and mechanical properties of A356 alloy were investigated.The results indicate that the combined addition of Al-3Ti-4.35La intermediate alloy and Sr can improve the microstructure and enhance the mechanical properties of A356 alloy.After adding 0.3wt.%Al-3Ti-4.35La and 0.03wt.%Sr to the as-cast A356 alloy,the average grain size ofα-Al decreases from 693.47μm to 264.13μm(a decrease of 61.91%),the secondary dendrite arm spacing(SDAS)is decreased by 47.8%from 32.09μm to 16.75μm,and the eutectic Si is transformed from an acicular structure to short rods and a granular structure.The ultimate tensile strength(UTS)and elongation(EL)of the as-cast A356 alloy modified by Al-3Ti-4.35La and Sr reach 216.3 MPa and 10.6%,which are enhanced by 29.54%and 134.66%compared with the unmodified alloy,respectively.The fracture mode is transformed from transgranular fracture to intergranular fracture,and the ductile toughness of the alloy is improved.After adding the Al-3Ti-4.35La and Sr,the undercooling for the nucleation ofα-Al and eutectic Si increases,leading to an accelerated nucleation rate and an increased number of nuclei,which shortens the duration of the eutectic reaction and consequently inhibits grain growth.
基金supported by the National Natural Science Foundation of China(52171030)the National Key Research and Development Program of China(2018YFA0702903).
文摘Grain refinement is a satisfying method to enhance the comprehensive performance of Mg alloys,and using grain refiners to improve the quality of Mg castings has become a common practice in the current casting industry.In this study,the effects of Al-CeO_(2)-Mg grain refiner addition on microstructure,cast fluidity,and mechanical properties of AZ91 alloy were systemically investigated by OM,SEM,DSC,TEM,sand Archimedean spiral mold fluidity test,and tensile test.The results show that the Al-CeO_(2)-Mg grain refiner has a remarkable effect on as-cast AZ91 alloy including notable grain refinement,enhancement of cast fluidity,and improvement of tensile properties.The average grain size of AZ91 alloy is refined by 63%with 1.0wt.%Al-CeO_(2)-Mg grain refiner.Meanwhile,the casting flow length of the as-cast AZ91 alloy is increased from 332 mm to 440 mm.The improvement of cast fluidity is attributed to the decreased liquidus temperature,shortening of solid-liquid two-phase temperature range,and refinement of microstructure.
基金Financial supports from the National Natural Science Foun-dation of China(Nos.52222409,52074132,U19A2084,and U22A20109)are greatly acknowledgedPartial financial support came from the National Key Research and Development Program(No.2022YFE0122000)+1 种基金the Interdisciplinary Integration and Inno-vation Project of JLU(No.JLUXKJC2021ZZ08)the Fundamental Research Funds for the Central Universities,JLU.
文摘The mechanical properties of as-cast metallic materials depend strongly on the size and shape of grains,which are critical microstructural parameters dictated by the interplay of nucleation and growth of crys-talline solids during solidification.In our experiments,the microstructure transition from coarse colum-nar crystals into fine equiaxed crystals for dilute Al-Mn-Si alloys was achieved by using sub-rapid so-lidification with the addition of Al-5Ti-1B grain refiner.The average grain size of Al alloy was reduced from a millimeter size to 73μm.Through temperature gradient calculation,we found that the acqui-sition of fine equiaxed crystals could be attributed to the existence of a high number density of TiB2,acting as effective nucleation sites with an increase in total undercooling.Furthermore,the curvature su-percooling,constitutional undercooling,thermal undercooling,and kinetic undercooling during sub-rapid solidification were quantitatively determined for given solidification rates.Our results showed that con-stitutional undercooling,rather than thermal undercooling,was primarily responsible for the formation of fine equiaxed grains,with the assistance of Al-5Ti-1B grain refiner.This work provides a new insight into the grain refining mechanism under sub-rapid solidification.
基金supported by the National Natural Science Foundation of China(No.U2102212)and the Shanghai Rising-Star Program(No.21QA1403200).
文摘Al-Si alloys have excellent corrosion resistance,low thermal expansion coefficient,and high strength-to-weight ratio,which make them widely used in structural components in the automotive and aerospace industries[1,2].However,the coarseα-Al dendrites result in poor mechanical properties[3,4],and the widely used Al-5Ti-B(all compositions are in wt.%unless otherwise specified)refiner fails in as-cast aluminum alloys with high silicon content(≥5 wt.%)due to the Si-poisoning effect[5,6].Fortunately,in order to overcome Si-poisoning,a series of refiners have been developed.Al-B refiner is effective for refining aluminum alloys with high silicon content,but it is easy to be poisoned by Ti/Zr[7,8].Al-Nb-B[9–11]and Al-V-B[12]refiners have a certain ability to overcome Si-poisoning,while the nucleating particles have a large density and are easy to agglomerate and settle,leading to the grain refinement fading phenomenon.Al-Ti-C-B refiner realizes the anti-Si/Zrpoisoning ofα-Al grain refinement based on the evolving effect of a doped TCB complex[13,14].Al-Ti-Nb-B refiner prepared with Nb partially substituted Ti can improve the refinement level of Al-10Si alloy to 109–125μm[15,16].However,the existing preparation method of the refiner uses pure Nb powder as raw material,resulting in high preparation costs,which limits its application in industry to a certain extent.
基金Project(2012CB619503)supported by the Natioanl Basic Research Program of ChinaProject(2013AA031001)supported by the National High-tech Research and Development Program of ChinaProject(2012DFA50630)supported by the International Science&Technology Cooperation Program of China
文摘To investigate the effects of Al-Ti-B-RE grain refiner on microstructure and mechanical properties of Al-7.0Si-0.55Mg （A357） alloy, some novel Al-7.0Si-0.55Mg alloys added with different amount of Al-STi-1B-RE grain refiner with different RE composition were prepared by vacuum-melting. The microstructure and fracture behavior of the AI-7.0Si-0.55Mg alloys with the grain refiners were observed by X-ray diffraction （XRD）, optical microscopy （OM）, scanning electron microscopy （SEM）, and the mechanical properties of the alloys were tested in mechanical testing machine at room temperature. The observation of AI-Ti-B-RE morphology and internal structure of the particles reveals that it exhibits a TiAl3/Ti2Al20RE core-shell structure via heterogeneous TiB2 nuclei. The tensile strength of Al-7.0Si-0.55Mg alloys with Al-5Ti-1B-3.0RE grain refiner reaches the peak value at the same addition （0.2%） of grain refiner.
文摘A novel type nano TiN/Ti composite grain refiner （TiN/Ti refiner） was prepared by high energy ball milling, and its effect on as-cast and hot-working microstructure of commercial purity aluminum （pure Al） was investigated. The results show that TiN/Ti refiner exhibits excellent grain refining performances on pure Al. With an addition of 0.2% TiN/Ti refiner, the average grain size of pure Al decreases to 82 μm, which is smaller than that of pure Ti and Al 5Ti 1B master alloy as refiners. The microstructure of weld joint of pure Al with 0.1% TiN/Ti refiner is fine equiaxed grains and the hardness of weld joint is higher than that of the base metal. For pure Al with 40% cold deformation and recrystallization at 250 °C for 1.0 h, the grains of the sample added 0.1% Ti powder have an obvious grain growth behavior. In contrast, oriented grains caused by deformation have been eliminated, and there is no obvious grain growth in pure Al refined with 0.1% TiN/Ti refiner, indicating that nano TiN in the refiner inhibits the growth of grain during recrystallization.
文摘Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refiner plates is of significance to the wood industry. It may affect refining quality, production efficiency, and power consumption. In this paper, the abrasion resistance of the refiner plate made of different materials, the stainless steels and high chromium cast irons, were tested and compared. The results showed that abrasion resistance of refiner plate made of high chromium cast irons was better than that of the stainless steel materials. Although the two kinds of materials have the same compositions, their abrasion resistances have ap-parent difference. The main reason is that the material microstructures have very important effects on their performance. The refiner plates made of developed high chromium cast irons don抰 demand the complex heat treatment. This can simplify the producing process, save the cost of production, decrease labor strength, and increase the production efficiency.
基金Project supported by the Natural Science Foundation of Shanxi Province (20011047)Patent Generalization Project ofShanxi Province (051025)
文摘Al-Ti-C grain refiner was prepared by SHS （self-propagating high-temperature synthesis ）-melting technique. The effect of La on the microstructures of grain refiner was studied by OM, TEM, SEM, XRD, and EDS. The experimental results indicate that La can improve the wettability between liquid aluminum and graphite ; the addition of La results in dispersive distribution of TiAl3 and TiC particles in the matrix. An excellent grain refining performance of Al-Ti-C grain refiner on commercially pure Al was obtained.
基金supported by the Natural Science Foundation of Inner Mongolia Autonomous Region(Grant No.2021MS05049)the Youth Fund Project of State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization(Grant No.2021Z2348)the Project of China North Rare Earth(Group)High-tech Co.,Ltd.(Grant No.2020H2177).
文摘To investigate the effect of rare earth on size and distribution of TiB2 phase in aluminum alloy refiner,Al-5Ti-1B-RE master alloy was fabricated,and its microstructure and phase constitutions were investigated by the combination of first principles calculations and experimental investigation.The calculated results reveal that Ce has the most effective modification ability due to the most positive adsorption energy and the largest charge transfer value compared with other rare earth elements.Results of experimental investigation indicate that the addition of rare earth in the Al-5Ti-1B alloys can greatly refine the particle size of TiB2,improve the distribution of particles and lead to better refinement effect than that of the Al-5Ti-1B alloys without rare earth.Moreover,Ce has the best optimization effect,which agrees well with the calculated results.
基金Project(51174177)supported by the National Natural Science Foundation of China
文摘An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.
文摘1 INTRODUCTIONWood chip refining is the most critical step in mechanical pulping.Commercical experi-ences have been gained for years.Modelling and control of chip refiners,however,pose a challenge mainly because of the stochastic nature of the process.Some attemptshave been made to employ factor analysis technique[1]in the modelling andsimulating of refiner operation[2,3].Strand[2]used common factors as links betweenintrinsic fibre properties and pulp quality.He believed that a qualitative concept onthe physical nature of these common factors could be arrived at,and thus would helpto understand what refining variables need to be controlled or adjusted in order to im-prove pulp quality.However,the linear model used in factor analysis is based on theassumption that the interactions among the system variables are linear,which,ofcourse,is not true in practice.
文摘A novel grain refiner composed of nickel, tungsten and yttria was prepared by the powder metallurgy way. The mierostructure of the refiner alloy was studied by optical microscope （OM）, scanning electron microscope （SEM） and energy dispersive spectroscopy （EDS）. The refinement process was simplized. It was shown that the alloy grains could be refined by addition of the refiners apparently even at high pouring temperature. The average grain size of the refiner free alloy was 4 mm, and 0.4 mm for the refined alloy. The fine-grain superalloy has excellent mechanical properties at intermediate temperature. The refinement mechanism was discussed.
文摘It was discussed how refiner plate is produced by a new process, such as three dimension making die with computer technology, shell molding, optimizing the alloy and controlling shakeout time with computer. Results confirmed that lead-time was decreased and product customization was improved in making die by using computer technology. At the same time, precision molding can decrease the reject ratio of refiner plates, and optimizing the alloy and shakeout time can eliminate the need for heat treatment. The new fabricating process showed several advantages over the traditional process in increasing toughness, better casting precision, elimination of the annealing treatment stage and raising production efficiency.
文摘The Al-5Cu alloys were prepared by different treatment methods,including adding a refiner Al-5Ti-1B,exerting a rotating magnetic field(RMF),and compound treatment of both refiner and RMF.The effects of treatment methods on the microstructure,properties,and solid solubility of the Al-5Cu alloy were investigated.The optimal magnetic field parameters and addition amount of refiner were confirmed by experiment.Results show that either RMF or adding refiner Al-5Ti-1B alone can refine the grain size,and the refining effect can be further improved by a compound refining treatment with optimized magnetic field parameters(120 A current and 8 Hz frequency) and 1.0wt.% Al-5Ti-1B refiner(RMF*+Al-5Ti-1B*).The average grain size is decreased to 68.1 μm,which is 60.8%,21.1%,and 83.5% lower than that of the alloy treated by the optimized rotating magnetic field,the Al-5Ti-1B refiner,and the alloy without any treatment,respectively.The tensile strength and elongation of the alloy reach 232.5 MPa and 18.6%,respectively,which are obviously higher than those of the alloys treated by rotating magnetic field,Al-5Ti-1B refiner,and the alloy without any treatment,respectively.Additionally,the solid solubility of the alloy is also obviously improved compared to the alloys treated by other methods.
基金funding by the National Natural Science Foundation (Grant No. 50745048)
文摘Straight-and curved-bar refining plates are two important types of plates commonly used in disc refiners in the papermaking industry.Theoretically,the curved-bar refining plate has a relatively uniform bar interaction angle,which indicates uniform refining effects.The bar angle of the curved bar was proposed and two typical curved-bar plates,the three-stage radial curved-bar plate and isometric curved-bar plate,were designed in this paper.The arc equations of the curved-bar center line and curved-bar edges were established and finally,the specific edge load(SEL)of the curved-bar plate was derived.The determination of bar parameters was discussed,which provides a theoretical basis for the design of curved-bar plates.
文摘Disc refiner is a critical equipment in the pulping and papermaking industry, pulp is refined in the refining zone, and different bar structures of refining disc constitute the different refining zones. With the use of the 3D modeling software SOLIDWORKS, five different refining discs that are commonly used in low consistency pulping, were built. The five refining discs were simulated and analyzed using the Computational Fluid Dynamics(CFD)software. The distribution of pulp velocity and surface shear stress, which is displayed between the bar and groove structures, can indirectly show the stress conditions on the refining discs. This paper provides a theoretical basis for research on the bar and groove failure of the refining discs.
基金Funded by National Natural Science Foundation of China(No.50774023)
文摘An electrostrictive uniaxial ultrasonic levitation reaction system was designed to perform TiC synthesis reaction by suspending graphite powder in Al-3Ti melt and an Al-3Ti-0.15C grain refiner alloy was obtained. The results show that sound pressure node in which graphite suspends is formed in the melt between radiation block and reflecting board by ultrasonic and TiAl3 particles congregate around C powder. Meanwhile, due to ultrasonic cavitation, dissolved TiAl3 provides better surface condition for the synthesis reaction of TiC. The reaction route is that C and dissolved Ti react to form TiC. Ultrasonic cavitation has a thermal activation effect on TiC particles and Al-3Ti-0.15C refiner has excellent microstructural refining effect on α-Al.
基金funding from the National Natural Science Foundation of China (Grant No. 50745048)Shaanxi Provincial Key Research and Development Project (Grant No. 2020 GY-105)Natural Science Basic Research Program of Shaanxi (Grant No. 2023-JC-QN-0154)。
文摘Power consumption is the energy source of the impact on fibers or pulp during low-consistency(LC)pulp refining,and the strength of refining affects refining quality and efficiency.The pulp properties,operating parameters,and bar parameters of the refiner plates are important parameters affecting refining efficiency,which can be defined as the ratio of net to total refining power.In this study,LC refining trials for pulps with different consistencies and fiber lengths were conducted using five isometric straightbar plates with different bar angles to explore the influences of the plate bar angle and pulp properties on the no-load power,impact capacity on fibers and refining efficiency.It was found that the no-load power of the LC refining process decreased with an increase in the plate bar angle while increased when pulp with higher consistency was refined under the same refining conditions.However,the effect of pulp consistency on the no-load power can be neglected when refining is conducted using plates with larger bar angles.Meanwhile,a critical bar angle for straight-bar plates in LC refining may exist,which has the strongest impact on the pulp and highest refining efficiency under the same refining conditions.In addition,the impact capacity of the plate on the pulp and refining efficiency in LC refining can be enhanced by appropriately increasing the pulp consistency and average fiber length when the bar angle of the refiner plate with a sector angle of 40°is less than 30°.Therefore,the efficiency and power consumption of the LC refining process can be adjusted by optimizing the pulp consistency and bar parameters of the refining plates.
文摘Currently ＂The Crude Formulation Technique＂ developed by the SINOPEC Research Institute of Petroleum Processing（RIPP） has passed the technical review sponsored by the Sinopec Corp.This technique by means of adopting the advanced algorithm on the basis of the crude assay data bank and the large crude spectroscopic database can intelligently blend together different kinds of crude oils to obtain multiple crude formulations, the quality of which is quite close to the target crude in a bid to provide technical support to the refining enterprises in the area of crude procurement and sustained property stabilization of crude oils pro-cessed thereby.
