Flip-chip technology is widely used in integrated circuit(IC)packaging.Molded underfill transfer molding is the most common process for these products,as the chip and solder bumps must be protected by the encapsulatin...Flip-chip technology is widely used in integrated circuit(IC)packaging.Molded underfill transfer molding is the most common process for these products,as the chip and solder bumps must be protected by the encapsulating material to ensure good reliability.Flow-front merging usually occurs during the molding process,and air is then trapped under the chip,which can form voids in the molded product.The void under the chip may cause stability and reliability problems.However,the flow process is unobservable during the transfer molding process.The engineer can only check for voids in the molded product after the process is complete.Previous studies have used fluid visualization experiments and developed computational fluid dynamics simulation tools to investigate this issue.However,a critical gap remains in establishing a comprehensive three-dimensional model that integrates two-phase flow,accurate venting settings,and fluid surface tension for molded underfill void evaluation—validated by experimental fluid visualization.This study aims to address this gap in the existing literature.In this study,a fluid visualization experiment was designed to simulate the transfer molding process,allowing for the observation of flow-front merging and void formation behaviors.For comparison,a three-dimensional mold flow analysis was also performed.It was found that the numerical simulation of the trapped air compression process under the chip was more accurate when considering the capillary force.The effect of design factors is evaluated in this paper.The results show that the most important factors for void size are fluid viscosity,the gap height under the chip,transfer time,contact angle between the fluid and the contact surfaces,and transfer pressure.Specifically,a smaller gap height beneath the chip aggravates void formation,while lower viscosity,extended transfer time,reduced contact angle,and increased transfer pressure are effective in minimizing void size.The overall results of this study will be useful for product and process design in selecting appropriate solutions for IC packaging,particularly in the development of void-free molded-underfill flip-chip packages.These findings support the optimization of industrial packaging processes in semiconductor manufacturing by guiding material selection and process parameters,ultimately enhancing package reliability and yield.展开更多
During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a rest...During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.展开更多
Sorghum is an important cereal crop for smallholder farmers’ food security in many countries in West Africa. However, its production has stagnated due to several factors, such as anthracnose and grain molds. Thus, a ...Sorghum is an important cereal crop for smallholder farmers’ food security in many countries in West Africa. However, its production has stagnated due to several factors, such as anthracnose and grain molds. Thus, a study was conducted to identify local germplasms that combine high grain yield and resistance to anthracnose and grain molds under Senegalese environments. A set of 256 genotypes was assessed at Sefa, Sinthiou and Kolda research stations using an incomplete blocks design with two replications. Agro-morphological and phytopathological data were collected. The results revealed a huge phenotypic variation between the genotypes for all traits. The flowering time varied from 43 to 126 days after sowing, while the panicle length varied from 10 to 60 cm. The genotypes were generally more productive at Sinthiou (1653 Kg ha−1) compared to Kolda (164 kg ha−1) research stations. The disease parameters were significantly and positively associated, while the flowering time was strongly and positively associated to grain mold score. The genotypes were classified into three groups with plant height, panicle diameter and length, flowering time and grain mold score as the most discriminating parameters. The genotypes belonging to cluster 3, in addition of being more productive and more resistant to grain mold and anthracnose, have longer panicles. These genotypes present promising prospects for inclusion in breeding programs focused on advancing sorghum yield and disease resistance in Senegal.展开更多
This paper reviews the research progress on mold detection technologies in milk and dairy products,including rapid test sheet methods,molecular biological detection techniques,metabolomics detection techniques,enzyme-...This paper reviews the research progress on mold detection technologies in milk and dairy products,including rapid test sheet methods,molecular biological detection techniques,metabolomics detection techniques,enzyme-linked immunosorbent assay(ELISA),and microbial rapid photoelectric detection systems,aiming to provide optimal choices for mold detection.展开更多
A coupled computational model of molten steel within the mold was developed,encompassing electromagnetic fields,fluid flow,heat transfer,shell formation,stress,and strain.The model was verified through comparison with...A coupled computational model of molten steel within the mold was developed,encompassing electromagnetic fields,fluid flow,heat transfer,shell formation,stress,and strain.The model was verified through comparison with plant measurements,showing reasonable agreement in electromagnetic field distribution,solidification endpoint,and shell thickness.Results indicate that coordinating the submerged entry nozzle(SEN)and mold electromagnetic stirring(M-EMS)effectively regulates the solidification quality of the initial shell.Adjusting M-EMS current frequency changes the impact position of the molten steel jet from the four-port SEN,while increasing current intensity reduces the jet impact intensity.Adjusting the M-EMS parameters can enhance the initial shell uniformity.Furthermore,in areas directly impacted by the steel jet from the four-port SEN,a relationship between brittle temperature range(BTR)width and total mechanical strain was found,and the larger the BTR width,the smaller the corresponding total mechanical strain.The BTR width provides a discriminant method to avoid hot tearing.Appropriate M-EMS parameters are obtained and applied,and the plant trials show a significant improvement in hot tearing near the surface of round blooms.展开更多
Interstitial oxygen(O)contamination remains a substantial challenge for metal injection molding(MIM)of titanium alloys.Herein,this critical problem is successfully addressed by regulating the thermal debinding tempera...Interstitial oxygen(O)contamination remains a substantial challenge for metal injection molding(MIM)of titanium alloys.Herein,this critical problem is successfully addressed by regulating the thermal debinding temperature and incorporating the oxygen scavenger LaB_(6).Results indicate that the surface oxide layer(with a thickness of(13.4±0.5)nm)of Ti_(6)Al4V powder begins to dissolve into the Ti matrix within the temperature range of 663–775℃.O contamination in MIM Ti alloys can be effectively mitigated by lowering the thermal debinding temperature and adding LaB6powder.As a result of reduced dissolved O content,the slips of mixedanddislocations are effectively accelerated,leading to improved ductility.Moreover,grain refinement,along with the in situ formation of Ti B whiskers and second-phase La_(2)O_(3)particles,enhances the strength of the material.The fabricated MIM Ti6Al4V sample exhibits excellent mechanical properties,achieving an ultimate tensile strength of(967±5)MPa,a yield strength of(866±8)MPa,and an elongation of 21.4%±0.7%.These tensile properties represent some of the best results reported in the literature for MIM Ti_(6)Al4V alloys.This study offers valuable insights into the development of high-performance MIM Ti alloys and other metal materials.展开更多
Steel–flux reactions involving the high aluminum(0.75–3.85 wt.%Al)low manganese(2.2 wt.%Mn)steel and the 18 wt.%SiO_(2)–18 wt.%Al2O3 mold flux were investigated.The results indicated that the reaction rate increase...Steel–flux reactions involving the high aluminum(0.75–3.85 wt.%Al)low manganese(2.2 wt.%Mn)steel and the 18 wt.%SiO_(2)–18 wt.%Al2O3 mold flux were investigated.The results indicated that the reaction rate increased when the initial aluminum content increased from 0.76 to 3.85 wt.%.Utilizing the two-film theory,a steel–flux reaction kinetic model controlled by mass transfer was established,which considered the influence of the initial composition on the density of liquid steel and flux.The mass transfer of aluminum in the steel phase was the reaction rate-determining step.It was confirmed that the mass transfer coefficient of Al was 1.87×10^(−4).The predicted results of the kinetic model were consistent and reliable with the experimental results.Thermodynamic equilibrium calculation was performed using FactSage 8.2,which was compared with the steel and flux final composition after 30 min.The content of initial aluminum in the liquid steel played a critical role in the SiO_(2)equilibrium content of the mold flux.In addition,the steel–flux reaction between[Al]and(SiO_(2))occurred with the initial SiO_(2)content in the mold flux lower than 3 wt.%.展开更多
Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generato...Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generators may require structural reinforcement or repair due to damage.This paper proposes a portable,on-site production method for molds under challenging conditions,where material supply is limited.The method utilizes large format additive manufacturing(LFAM)with recycled composite materials,sourced from end-of-life components and waste,as feedstock.The study investigates the microstructural effects of recycling through shredding techniques,using microscopic imaging.Three potential defense-sector applications are explored,specifically in the aerospace,automotive,and energy industries.Additionally,the influence of key printing parameters,particularly nonparallel plane deposition at a 45-degree angle,on the mechanical behavior of ABS reinforced with 20%glass fiber(GF)is examined.The results demonstrate the feasibility of this manufacturing approach,highlighting reductions in waste material and production times compared to traditional methods.Shorter layer times were found to reduce thermal gradients between layers,thereby improving layer adhesion.While 45-degree deposition enhanced Young's modulus,it slightly reduced interlayer adhesion quality.Furthermore,recycling-induced fiber length reduction led to material degradation,aligning with findings from previous studies.Challenges encountered during implementation included weak part adherence to the print bed and local excess material deposition.Overall,the proposed methodology offers a cost-effective alternative to traditional CNC machining for mold production,demonstrating its potential for on-demand manufacturing in resource-constrained environments.展开更多
In this study, shaking table tests were performed to investigate the dynamic characteristics of a mold transformer. Based on the test results, rotary friction dampers were developed to mitigate the excessive lateral d...In this study, shaking table tests were performed to investigate the dynamic characteristics of a mold transformer. Based on the test results, rotary friction dampers were developed to mitigate the excessive lateral displacement that occurred along the direction of the weak stiffness axis of the mold transformer. In addition, shaking table tests were performed by attaching friction dampers to both sides of the mold transformer. Based on the shaking table test results, the natural frequency, mode vector, and damping ratio of the mold transformer were derived using the transfer function and half-power bandwidth. The test results indicated that the use of friction dampers can decrease the displacement and acceleration response of the mold transformer. Finally, dynamic structural models were established considering the component connectivity and mass distribution of the mold transformer. In addition, a numerical strategy was proposed to calibrate the stiffness coefficients of the mold transformer, thereby facilitating the relationship between generalized mass and stiffness. The results indicated that the analytical model based on the calibration strategy of stiffness coefficients can reasonably simulate the dynamic behavior of the mold transformer using friction dampers with regard to transfer function, displacement, and acceleration response.展开更多
The influence of pouring temperature and mold temperature on the fluidity and hot tearing behavior of Al-2Li-2Cu-0.5Mg-0.15Sc-0.1Zr-0.1Ti alloys was investigated by experimental investigation and simulation assessment...The influence of pouring temperature and mold temperature on the fluidity and hot tearing behavior of Al-2Li-2Cu-0.5Mg-0.15Sc-0.1Zr-0.1Ti alloys was investigated by experimental investigation and simulation assessment.The results showed that the length of the spiral fluidity sample increases from 302 to 756 mm as the pouring temperature increases from 680 to 740℃,and from 293 to 736 mm as the mold temperature increases from 200 to 400℃.The hot tearing susceptibility(HTS)firstly decreases and then increases with increasing pouring and mold temperatures,which is mainly caused by the oxide inclusion originating from the high activity of Li at excessive pouring temperature.Excessive pouring and mold temperatures easily produce oxide inclusions and holes,leading to a reduction in fluidity and an increase in HTS of the alloy.Combining the experimental and simulation results,the optimized pouring and mold temperatures are~720℃ and~300℃ for the cast Al-Li alloy,respectively.展开更多
Controlling molten steel flow in the mold and stabilizing the meniscus are critical challenges during the continuous casting,directly impacting the surface quality and internal quality of the final steel slab product....Controlling molten steel flow in the mold and stabilizing the meniscus are critical challenges during the continuous casting,directly impacting the surface quality and internal quality of the final steel slab product.The effects of electromagnetic swirling flow in nozzle(EMSFN)technology on molten steel flow in the mold during slab continuous casting under various casting speeds were investigated.A real-time adjustable EMSFN was developed,and a three-dimensional unsteady Reynolds-averaged Navier–Stokes turbulence mathematical model was established to simulate the flow field within the mold.The results demonstrate that the EMSFN effectively stabilizes the outflow from nozzle,reduces the impact depth and surface velocity of the molten steel,mitigates meniscus fluctuations,and promotes stable flow within the mold.However,a certain matching relationship exists between the casting speed and the current intensity.For the experimental medium-thick slab specifications,the optimal current intensities were found to be 100,130,and 200 A at casting speeds of 1.0,1.5,and 2.0 m/min,respectively.EMSFN can optimize the mold flow field under different casting speeds,providing theoretical support for improving the quality of continuously cast slab products.展开更多
Selective laser melting(SLM)has become a critical technique for manufacturing molds with conformal cooling channels to achieve high cooling efficiencies.A novel selective laser-melted 718HH plastic mold steel with an ...Selective laser melting(SLM)has become a critical technique for manufacturing molds with conformal cooling channels to achieve high cooling efficiencies.A novel selective laser-melted 718HH plastic mold steel with an excellent combination of strength and toughness was investigated.After SLM fabrication,quenching and tempering are conducted as post-printing heat treatment(PPHT)to improve the mechanical properties of the as-built samples.Both the microstructure and the corresponding mechanical properties were systematically studied.The results show that PPHT facilitates the complete martensite transformation.Meanwhile,the retained austenite(γ)phase was still found in the as-built samples.And high-density dislocations were dispersively distributed within the martensite matrix for both as-built and as-PPHTed samples.After PPHT,due to the recovery and recrystallization of martensite,reduced dislocation density and increased high-angle grain boundaries,the microhardness of the as-built samples decreased from 498.8±16.7 to 382.1±5.0 HV0.3.Correspondingly,the strength,including the ultimate tensile strength and yield strength,of the as-built and as-PPHTed samples also decreased from 1411.3±17.8 to 1208.7±3.2 MPa and 1267.3±11.7 to 1084.7±5.1 MPa,respectively.On the contrary,the value of impact energy significantly increased from 15.3±1.2 J(as-built)to 39.7±1.2 J(as-PPHTed).Notably,the mechanical properties of SLMed 718HH samples are significantly better than those of corresponding wrought samples.展开更多
The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Bas...The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.展开更多
Effectiveness and safety of a sports mouthguard depend on its thickness and material, and the thermoforming process affects these. The purpose of this study was to clarify the effects of differences in molding mechani...Effectiveness and safety of a sports mouthguard depend on its thickness and material, and the thermoforming process affects these. The purpose of this study was to clarify the effects of differences in molding mechanisms on the lower molding temperature limit and molding time in dental thermoforming. Ethylene vinyl acetate resin mouthguard sheet and two thermoforming machines;vacuum blower molding machine and vacuum ejector/pressure molding machine were used. The molding pressures for suction molding were −0.018 MPa for vacuum blower molding and −0.090 MPa for vacuum ejector molding, and for pressure molding was set to 0.090 MPa or 0.450 MPa. Based on the manufacturer’s standard molding temperature of 95˚C, the molding temperature was lowered in 2.5˚C increments to determine the lower molding temperature limit at which no molding defects occurred. In order to investigate the difference in molding time depending on the molding mechanism, the duration of molding pressure was adjusted in each molding machine, and the molding time required to obtain a sample without molding defects was measured. The molding time of each molding machine were compared using one-way analysis of variance. The lower molding temperature limit was 90.0˚C for the vacuum blower machine, 77.5˚C for the vacuum ejector machine, 77.5˚C for the pressure molding machine at 0.090 MPa, and 67.5˚C for the pressure molding machine at 0.45 MPa. The lower molding temperature limit was higher for lower absolute values of molding pressure. The molding time was shorter for pressure molding than for suction molding. Significant differences were observed between all conditions except between the pressure molding machine at 0.090 MPa and 0.45 MPa (P < 0.01). A comparison of the differences in lower molding temperature limit and molding time due to molding mechanisms in dental thermoforming revealed that the lower molding temperature limit depends on the molding pressure and that the molding time is longer for suction molding than for pressure molding.展开更多
文摘Flip-chip technology is widely used in integrated circuit(IC)packaging.Molded underfill transfer molding is the most common process for these products,as the chip and solder bumps must be protected by the encapsulating material to ensure good reliability.Flow-front merging usually occurs during the molding process,and air is then trapped under the chip,which can form voids in the molded product.The void under the chip may cause stability and reliability problems.However,the flow process is unobservable during the transfer molding process.The engineer can only check for voids in the molded product after the process is complete.Previous studies have used fluid visualization experiments and developed computational fluid dynamics simulation tools to investigate this issue.However,a critical gap remains in establishing a comprehensive three-dimensional model that integrates two-phase flow,accurate venting settings,and fluid surface tension for molded underfill void evaluation—validated by experimental fluid visualization.This study aims to address this gap in the existing literature.In this study,a fluid visualization experiment was designed to simulate the transfer molding process,allowing for the observation of flow-front merging and void formation behaviors.For comparison,a three-dimensional mold flow analysis was also performed.It was found that the numerical simulation of the trapped air compression process under the chip was more accurate when considering the capillary force.The effect of design factors is evaluated in this paper.The results show that the most important factors for void size are fluid viscosity,the gap height under the chip,transfer time,contact angle between the fluid and the contact surfaces,and transfer pressure.Specifically,a smaller gap height beneath the chip aggravates void formation,while lower viscosity,extended transfer time,reduced contact angle,and increased transfer pressure are effective in minimizing void size.The overall results of this study will be useful for product and process design in selecting appropriate solutions for IC packaging,particularly in the development of void-free molded-underfill flip-chip packages.These findings support the optimization of industrial packaging processes in semiconductor manufacturing by guiding material selection and process parameters,ultimately enhancing package reliability and yield.
基金financially supported by the National Natural Science Foundation of China(Nos.52274315 and 52374320)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-22-011A1 and FRF-DF22-16)。
文摘During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.
文摘Sorghum is an important cereal crop for smallholder farmers’ food security in many countries in West Africa. However, its production has stagnated due to several factors, such as anthracnose and grain molds. Thus, a study was conducted to identify local germplasms that combine high grain yield and resistance to anthracnose and grain molds under Senegalese environments. A set of 256 genotypes was assessed at Sefa, Sinthiou and Kolda research stations using an incomplete blocks design with two replications. Agro-morphological and phytopathological data were collected. The results revealed a huge phenotypic variation between the genotypes for all traits. The flowering time varied from 43 to 126 days after sowing, while the panicle length varied from 10 to 60 cm. The genotypes were generally more productive at Sinthiou (1653 Kg ha−1) compared to Kolda (164 kg ha−1) research stations. The disease parameters were significantly and positively associated, while the flowering time was strongly and positively associated to grain mold score. The genotypes were classified into three groups with plant height, panicle diameter and length, flowering time and grain mold score as the most discriminating parameters. The genotypes belonging to cluster 3, in addition of being more productive and more resistant to grain mold and anthracnose, have longer panicles. These genotypes present promising prospects for inclusion in breeding programs focused on advancing sorghum yield and disease resistance in Senegal.
基金Supported by Research Project on Food Detection Technology Innovation and Standard Integration 2024(YNXM-2024-FW-019).
文摘This paper reviews the research progress on mold detection technologies in milk and dairy products,including rapid test sheet methods,molecular biological detection techniques,metabolomics detection techniques,enzyme-linked immunosorbent assay(ELISA),and microbial rapid photoelectric detection systems,aiming to provide optimal choices for mold detection.
基金supported by Zhongyuan Special Steel Equipment Manufacturing Co.,Ltd.,China.
文摘A coupled computational model of molten steel within the mold was developed,encompassing electromagnetic fields,fluid flow,heat transfer,shell formation,stress,and strain.The model was verified through comparison with plant measurements,showing reasonable agreement in electromagnetic field distribution,solidification endpoint,and shell thickness.Results indicate that coordinating the submerged entry nozzle(SEN)and mold electromagnetic stirring(M-EMS)effectively regulates the solidification quality of the initial shell.Adjusting M-EMS current frequency changes the impact position of the molten steel jet from the four-port SEN,while increasing current intensity reduces the jet impact intensity.Adjusting the M-EMS parameters can enhance the initial shell uniformity.Furthermore,in areas directly impacted by the steel jet from the four-port SEN,a relationship between brittle temperature range(BTR)width and total mechanical strain was found,and the larger the BTR width,the smaller the corresponding total mechanical strain.The BTR width provides a discriminant method to avoid hot tearing.Appropriate M-EMS parameters are obtained and applied,and the plant trials show a significant improvement in hot tearing near the surface of round blooms.
基金financially supported by the National Natural Science Foundation of China(Nos.52274359 and 52304379)Beijing Natural Science Foundation,China(No.L212021)+4 种基金China National Postdoctoral Program for Innovative Talents(No.BX20220034)China Postdoctoral Science Foundation(No.2022M720403)Fundamental Research Funds for the Central Universities,China(Nos.FRFTP-19005C1Z and 00007718)AECC University Research Cooperation Project,China(No.HFZL2021CXY021)State Key Lab of Advanced Metals and Materials,University of Science and Technology Beijing,China(Nos.2021Z-03 and 2022Z-14)。
文摘Interstitial oxygen(O)contamination remains a substantial challenge for metal injection molding(MIM)of titanium alloys.Herein,this critical problem is successfully addressed by regulating the thermal debinding temperature and incorporating the oxygen scavenger LaB_(6).Results indicate that the surface oxide layer(with a thickness of(13.4±0.5)nm)of Ti_(6)Al4V powder begins to dissolve into the Ti matrix within the temperature range of 663–775℃.O contamination in MIM Ti alloys can be effectively mitigated by lowering the thermal debinding temperature and adding LaB6powder.As a result of reduced dissolved O content,the slips of mixedanddislocations are effectively accelerated,leading to improved ductility.Moreover,grain refinement,along with the in situ formation of Ti B whiskers and second-phase La_(2)O_(3)particles,enhances the strength of the material.The fabricated MIM Ti6Al4V sample exhibits excellent mechanical properties,achieving an ultimate tensile strength of(967±5)MPa,a yield strength of(866±8)MPa,and an elongation of 21.4%±0.7%.These tensile properties represent some of the best results reported in the literature for MIM Ti_(6)Al4V alloys.This study offers valuable insights into the development of high-performance MIM Ti alloys and other metal materials.
基金support from the National Key R&D Program of China(No.2023YFB3709900)the National Natural Science Foundation of China(Grant No.U22A20171).
文摘Steel–flux reactions involving the high aluminum(0.75–3.85 wt.%Al)low manganese(2.2 wt.%Mn)steel and the 18 wt.%SiO_(2)–18 wt.%Al2O3 mold flux were investigated.The results indicated that the reaction rate increased when the initial aluminum content increased from 0.76 to 3.85 wt.%.Utilizing the two-film theory,a steel–flux reaction kinetic model controlled by mass transfer was established,which considered the influence of the initial composition on the density of liquid steel and flux.The mass transfer of aluminum in the steel phase was the reaction rate-determining step.It was confirmed that the mass transfer coefficient of Al was 1.87×10^(−4).The predicted results of the kinetic model were consistent and reliable with the experimental results.Thermodynamic equilibrium calculation was performed using FactSage 8.2,which was compared with the steel and flux final composition after 30 min.The content of initial aluminum in the liquid steel played a critical role in the SiO_(2)equilibrium content of the mold flux.In addition,the steel–flux reaction between[Al]and(SiO_(2))occurred with the initial SiO_(2)content in the mold flux lower than 3 wt.%.
基金financially supported by the Central Government Guiding Local Science and Technology Development Fund of Henan Province(Z20241471091)the Independent R&D Funds of State Key Laboratory of Advanced Metallurgy(41624025).
基金Generalitat Valenciana(GVA)and Spanish Ministry of Science and Innovation(Grant Nos.TED2021-130879 B-C21,CIACIF/2021/286,PID2023-151110OB-I00,and CIPROM/2022/3)to provide funds for conducting experiments and software licensessupported by the National Research Foundation,Prime Minister's Office,Singapore under its Campus for Research Excellence and Technological Enterprise(CREATE)programme。
文摘Military missions in hostile environments are often costly and unpredictable,with squadrons sometimes facing isolation and resource scarcity.In such scenarios,critical components in vehicles,drones,and energy generators may require structural reinforcement or repair due to damage.This paper proposes a portable,on-site production method for molds under challenging conditions,where material supply is limited.The method utilizes large format additive manufacturing(LFAM)with recycled composite materials,sourced from end-of-life components and waste,as feedstock.The study investigates the microstructural effects of recycling through shredding techniques,using microscopic imaging.Three potential defense-sector applications are explored,specifically in the aerospace,automotive,and energy industries.Additionally,the influence of key printing parameters,particularly nonparallel plane deposition at a 45-degree angle,on the mechanical behavior of ABS reinforced with 20%glass fiber(GF)is examined.The results demonstrate the feasibility of this manufacturing approach,highlighting reductions in waste material and production times compared to traditional methods.Shorter layer times were found to reduce thermal gradients between layers,thereby improving layer adhesion.While 45-degree deposition enhanced Young's modulus,it slightly reduced interlayer adhesion quality.Furthermore,recycling-induced fiber length reduction led to material degradation,aligning with findings from previous studies.Challenges encountered during implementation included weak part adherence to the print bed and local excess material deposition.Overall,the proposed methodology offers a cost-effective alternative to traditional CNC machining for mold production,demonstrating its potential for on-demand manufacturing in resource-constrained environments.
基金Basic Science Research Program of the National Research Foundation of Korea under Grant Nos.NRF-2020R1A6A1A03044977 and NRF2022R1A2C2004351。
文摘In this study, shaking table tests were performed to investigate the dynamic characteristics of a mold transformer. Based on the test results, rotary friction dampers were developed to mitigate the excessive lateral displacement that occurred along the direction of the weak stiffness axis of the mold transformer. In addition, shaking table tests were performed by attaching friction dampers to both sides of the mold transformer. Based on the shaking table test results, the natural frequency, mode vector, and damping ratio of the mold transformer were derived using the transfer function and half-power bandwidth. The test results indicated that the use of friction dampers can decrease the displacement and acceleration response of the mold transformer. Finally, dynamic structural models were established considering the component connectivity and mass distribution of the mold transformer. In addition, a numerical strategy was proposed to calibrate the stiffness coefficients of the mold transformer, thereby facilitating the relationship between generalized mass and stiffness. The results indicated that the analytical model based on the calibration strategy of stiffness coefficients can reasonably simulate the dynamic behavior of the mold transformer using friction dampers with regard to transfer function, displacement, and acceleration response.
基金financially supported by the National Natural Science Foundation of China(Nos.51871148,51821001)。
文摘The influence of pouring temperature and mold temperature on the fluidity and hot tearing behavior of Al-2Li-2Cu-0.5Mg-0.15Sc-0.1Zr-0.1Ti alloys was investigated by experimental investigation and simulation assessment.The results showed that the length of the spiral fluidity sample increases from 302 to 756 mm as the pouring temperature increases from 680 to 740℃,and from 293 to 736 mm as the mold temperature increases from 200 to 400℃.The hot tearing susceptibility(HTS)firstly decreases and then increases with increasing pouring and mold temperatures,which is mainly caused by the oxide inclusion originating from the high activity of Li at excessive pouring temperature.Excessive pouring and mold temperatures easily produce oxide inclusions and holes,leading to a reduction in fluidity and an increase in HTS of the alloy.Combining the experimental and simulation results,the optimized pouring and mold temperatures are~720℃ and~300℃ for the cast Al-Li alloy,respectively.
基金National Natural Science Foundation of China(Nos.U21A20117,52104347 and 52272078)the Fundamental Research Funds for the Central Universities(No.N2409006)Natural Science Foundation of Liaoning Province(2023-MSBA-135)for the financial support.
文摘Controlling molten steel flow in the mold and stabilizing the meniscus are critical challenges during the continuous casting,directly impacting the surface quality and internal quality of the final steel slab product.The effects of electromagnetic swirling flow in nozzle(EMSFN)technology on molten steel flow in the mold during slab continuous casting under various casting speeds were investigated.A real-time adjustable EMSFN was developed,and a three-dimensional unsteady Reynolds-averaged Navier–Stokes turbulence mathematical model was established to simulate the flow field within the mold.The results demonstrate that the EMSFN effectively stabilizes the outflow from nozzle,reduces the impact depth and surface velocity of the molten steel,mitigates meniscus fluctuations,and promotes stable flow within the mold.However,a certain matching relationship exists between the casting speed and the current intensity.For the experimental medium-thick slab specifications,the optimal current intensities were found to be 100,130,and 200 A at casting speeds of 1.0,1.5,and 2.0 m/min,respectively.EMSFN can optimize the mold flow field under different casting speeds,providing theoretical support for improving the quality of continuously cast slab products.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3702501)the National Science and Technology Major Project(J2019-VI-0019-0134).
文摘Selective laser melting(SLM)has become a critical technique for manufacturing molds with conformal cooling channels to achieve high cooling efficiencies.A novel selective laser-melted 718HH plastic mold steel with an excellent combination of strength and toughness was investigated.After SLM fabrication,quenching and tempering are conducted as post-printing heat treatment(PPHT)to improve the mechanical properties of the as-built samples.Both the microstructure and the corresponding mechanical properties were systematically studied.The results show that PPHT facilitates the complete martensite transformation.Meanwhile,the retained austenite(γ)phase was still found in the as-built samples.And high-density dislocations were dispersively distributed within the martensite matrix for both as-built and as-PPHTed samples.After PPHT,due to the recovery and recrystallization of martensite,reduced dislocation density and increased high-angle grain boundaries,the microhardness of the as-built samples decreased from 498.8±16.7 to 382.1±5.0 HV0.3.Correspondingly,the strength,including the ultimate tensile strength and yield strength,of the as-built and as-PPHTed samples also decreased from 1411.3±17.8 to 1208.7±3.2 MPa and 1267.3±11.7 to 1084.7±5.1 MPa,respectively.On the contrary,the value of impact energy significantly increased from 15.3±1.2 J(as-built)to 39.7±1.2 J(as-PPHTed).Notably,the mechanical properties of SLMed 718HH samples are significantly better than those of corresponding wrought samples.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174321,52274339 and 52074186).
文摘The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.
文摘Effectiveness and safety of a sports mouthguard depend on its thickness and material, and the thermoforming process affects these. The purpose of this study was to clarify the effects of differences in molding mechanisms on the lower molding temperature limit and molding time in dental thermoforming. Ethylene vinyl acetate resin mouthguard sheet and two thermoforming machines;vacuum blower molding machine and vacuum ejector/pressure molding machine were used. The molding pressures for suction molding were −0.018 MPa for vacuum blower molding and −0.090 MPa for vacuum ejector molding, and for pressure molding was set to 0.090 MPa or 0.450 MPa. Based on the manufacturer’s standard molding temperature of 95˚C, the molding temperature was lowered in 2.5˚C increments to determine the lower molding temperature limit at which no molding defects occurred. In order to investigate the difference in molding time depending on the molding mechanism, the duration of molding pressure was adjusted in each molding machine, and the molding time required to obtain a sample without molding defects was measured. The molding time of each molding machine were compared using one-way analysis of variance. The lower molding temperature limit was 90.0˚C for the vacuum blower machine, 77.5˚C for the vacuum ejector machine, 77.5˚C for the pressure molding machine at 0.090 MPa, and 67.5˚C for the pressure molding machine at 0.45 MPa. The lower molding temperature limit was higher for lower absolute values of molding pressure. The molding time was shorter for pressure molding than for suction molding. Significant differences were observed between all conditions except between the pressure molding machine at 0.090 MPa and 0.45 MPa (P < 0.01). A comparison of the differences in lower molding temperature limit and molding time due to molding mechanisms in dental thermoforming revealed that the lower molding temperature limit depends on the molding pressure and that the molding time is longer for suction molding than for pressure molding.
