Kid, Hurry and Grab Mom's hand. It's too dark around here——the road To the heaven. I'm afraid Something mav hurt your head. Hurry and Grab my hand. Let's move on Side by side.
In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollu...In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.展开更多
The effect of slow shot speed on externally solidified crystal(ESC),porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy was investigated by optical microscopy(OM),scanning electron mi...The effect of slow shot speed on externally solidified crystal(ESC),porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy was investigated by optical microscopy(OM),scanning electron microscopy(SEM)and laboratory computed tomography(CT).Results showed that the newly developed AlSi9MnMoV alloy exhibited improved mechanical properties when compared to the AlSi10MnMg alloy.The AlSi9MnMoV alloy,which was designed with trace multicomponent additions,displays a notable grain refining effect in comparison to the AlSi10MnMg alloy.Refining elements Ti,Zr,V,Nb,B promote heterogeneous nucleation and reduce the grain size of primaryα-Al.At a lower slow shot speed,the large ESCs are easier to form and gather,developing into the dendrite net and net-shrinkage.With an increase in slow shot speed,the size and number of ESCs and porosities significantly reduce.In addition,the distribution of ESCs is more dispersed and the net-shrinkage disappears.The tensile property is greatly improved by adopting a higher slow shot speed.The ultimate tensile strength is enhanced from 260.31 MPa to 290.31 MPa(increased by 11.52%),and the elongation is enhanced from 3.72%to 6.34%(increased by 70.52%).展开更多
Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further impro...Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further improve their mechanical properties.In this study,two-stage aging treatment with different pre-aging times was designed and employed to further improve the mechanical properties of HPDC Al8SiMgCuZn alloy.The characteristics of precipitates were evaluated by a transmission electron microscope(TEM),and the precipitation strengthening mechanism was discussed.The results reveal that the strengthening is mainly contributed by the precipitation ofβ″phase after two-stage aging,and the number density and size of the precipitates are significantly depended on the pre-aging time.The number density of precipitates is increased with the pre-aging time prolonged from 0 h to 4 h,and then decreases with the further increase of pre-aging time from 4 h to 6 h.The precipitates with the highest density and smallest size are observed after pre-aging for 4 h.After pre-aged at 100℃for 4 h and then artificial aged at 200℃for 30 min,the yield strength of 207 MPa,ultimate tensile strength of 325 MPa and elongation of 7.6%are achieved.展开更多
Magnesium alloy is one of the lightest metal structural materials.The weight is further reduced through the hollow structure.However,the hollow structure is easily damaged during processing.In order to maintain the ho...Magnesium alloy is one of the lightest metal structural materials.The weight is further reduced through the hollow structure.However,the hollow structure is easily damaged during processing.In order to maintain the hollow structure and to transfer the stresses during the high temperature deformation,the sand mandrel is proposed.In this paper,the hollow AZ31 magnesium alloy three-channel joint is studied by hot extrusion forming.Sand as one of solid granule medium is used to fill the hollow magnesium alloy.The extrusion temperatures are 230℃ and 300℃,respectively.The process parameters(die angle,temperature,bottom thickness,sidewall thickness,edge-to-middle ratio in bottom,bottom shape)of the hollow magnesium alloy are analyzed based on the results of experiments and the finite element method.The results are shown that the formability of the hollow magnesium alloy will be much better when the ratio of sidewall thickness to the bottom thickness is 1:1.5.Also when edge-to-middle ratio in bottom is about 1:1.5,a better forming product can be received.The best bottom shape in these experiments will be convex based on the forming results.The grain will be refined obviously after the extrusion.Also the microstructures will be shown as streamlines.And these lines will be well agreement with the mold in the corner.展开更多
In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,met...In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,metallographic examination,and hardness test,the properties and causes of the cracks are discussed.The results indicate that the cracking type is intergranular brittle cracking,occurring during the forging stage.Furthermore,the recrystallization at the crack site is found to be incomplete,which is attributed to the low deformation temperature.展开更多
语义构建离不开认知识解因素。die of和die from可以与同样的表达式搭配,即die of X和die from X。就规约意义而言,die of X通常表达客观的、直接的原因,而die from X通常表达客观的、间接的原因。但在die of X和die from X语义构建过程...语义构建离不开认知识解因素。die of和die from可以与同样的表达式搭配,即die of X和die from X。就规约意义而言,die of X通常表达客观的、直接的原因,而die from X通常表达客观的、间接的原因。但在die of X和die from X语义构建过程中,通过认知识解,客观的、直接的原因会被识解为主观的、间接原因,客观的、间接的原因会被构建为主观的、直接的原因。展开更多
Aluminum high pressure die casting(HPDC)technology has evolved in the past decades,enabling stronger and larger one-piece casting with significant part consolidation.It also offers a higher design freedom for more mas...Aluminum high pressure die casting(HPDC)technology has evolved in the past decades,enabling stronger and larger one-piece casting with significant part consolidation.It also offers a higher design freedom for more mass-efficient thin-walled body structures.For body structures that require excellent ductility and fracture toughness to be joined with steel sheet via self-piercing riveting(for instance,shock towers and hinge pillars,etc.),a costly T7 heat treatment comprising a solution heat treatment at elevated temperatures(450℃-500℃)followed by an over-ageing heat treatment is needed to optimize microstructure for meeting product requirement.To enable cost-efficient mass production of HPDC body structures,it is important to eliminate the expensive T7 heat treatment without sacrificing mechanical properties.Optimizing die cast alloy chemistry is a potential solution to improve fracture toughness and ductility of the HPDC components.The present study intends to tailor the Mg and Cu additions for a new Al-Si-Cr type die casting alloy(registered as A379 with The Aluminum Association,USA)to achieve the desired tensile properties without using T7 heat treatment.It was found that Cu addition should be avoided,as it is not effective in enhancing strength while degrades tensile ductility.Mg addition is very effective in improving strength and has minor impact on tensile ductility.The investigated Al-Si-Cr alloy with a nominal composition of Al-8.5wt.%Si-0.3wt.%Cr-0.2wt.%Fe shows comparable tensile properties with the T7 treated AlSi10MnMg alloy which is currently used for manufacturing shock towers and hinge pillars.展开更多
The integrated circuit (IC) manufacturing process is capital intensive and complex. The production process of unit product (or die, as it is commonly referred to) takes several weeks. Semiconductor factories (fabs) co...The integrated circuit (IC) manufacturing process is capital intensive and complex. The production process of unit product (or die, as it is commonly referred to) takes several weeks. Semiconductor factories (fabs) continuously attempt to improve their productivity, as measured in output and cycle time (or mean flow time). The conflicting objective of producing maximum units at minimal production cycle time and at the highest quality, as measured by die yield, is discussed in this paper. The inter-related effects are characterized, and a model is proposed to address this multi-objective function. We then show that, with this model, die cost can be optimized for any given operating conditions of a fab. A numerical example is provided to illustrate the practicality of the model and the proposed optimization method.展开更多
在菲律宾发现的各种海龟都濒临灭绝。但是现在,许多过去收集海龟蛋吃或卖的人都在努力保护海龟的安全。All the kinds of sea turtles found in the Philippines are endangered.That means they are at risk of dying out.But now,the ...在菲律宾发现的各种海龟都濒临灭绝。但是现在,许多过去收集海龟蛋吃或卖的人都在努力保护海龟的安全。All the kinds of sea turtles found in the Philippines are endangered.That means they are at risk of dying out.But now,the turtles have one less threat.Many people who used to collect their eggs to eat or to sell are now working to keep turtles safe.展开更多
狗是非常忠诚的伙伴。即使一生中可能会有很多主人,它们也不会真正忘记自己的第一个主人。Jolie Mejía recently witnessed an undying devotion first hand while on a family trip to the beach.She was enjoying surfing in the...狗是非常忠诚的伙伴。即使一生中可能会有很多主人,它们也不会真正忘记自己的第一个主人。Jolie Mejía recently witnessed an undying devotion first hand while on a family trip to the beach.She was enjoying surfing in the district of Punta Negra in Lima,Peru when she noticed a stray dog gazing longingly out at the sea.展开更多
文摘Kid, Hurry and Grab Mom's hand. It's too dark around here——the road To the heaven. I'm afraid Something mav hurt your head. Hurry and Grab my hand. Let's move on Side by side.
文摘In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.
基金financially supported by the National Key Research and Development Program of China(2022YFB3404201)the Major Science and Technology Project of Changchun City,Jilin Province(Grant No.20210301024GX)。
文摘The effect of slow shot speed on externally solidified crystal(ESC),porosity and tensile property in a newly developed high-pressure die-cast Al-Si alloy was investigated by optical microscopy(OM),scanning electron microscopy(SEM)and laboratory computed tomography(CT).Results showed that the newly developed AlSi9MnMoV alloy exhibited improved mechanical properties when compared to the AlSi10MnMg alloy.The AlSi9MnMoV alloy,which was designed with trace multicomponent additions,displays a notable grain refining effect in comparison to the AlSi10MnMg alloy.Refining elements Ti,Zr,V,Nb,B promote heterogeneous nucleation and reduce the grain size of primaryα-Al.At a lower slow shot speed,the large ESCs are easier to form and gather,developing into the dendrite net and net-shrinkage.With an increase in slow shot speed,the size and number of ESCs and porosities significantly reduce.In addition,the distribution of ESCs is more dispersed and the net-shrinkage disappears.The tensile property is greatly improved by adopting a higher slow shot speed.The ultimate tensile strength is enhanced from 260.31 MPa to 290.31 MPa(increased by 11.52%),and the elongation is enhanced from 3.72%to 6.34%(increased by 70.52%).
基金financially supported by the Natural Science Foundation of Guangdong Province(Nos.2021A151510042,2021A1515011728)the China Postdoctoral Science Foundation(2022M711190)+1 种基金the National Natural Science Foundation of China(No.51875211)the Key Area Research and Development Program of Guangdong Province(No.2020B010186002)。
文摘Considering the components produced by high pressure die casting(HPDC)process usually with ultra-large sizes and complex morphologies,high temperature solid solution treatment is not a suitable method to further improve their mechanical properties.In this study,two-stage aging treatment with different pre-aging times was designed and employed to further improve the mechanical properties of HPDC Al8SiMgCuZn alloy.The characteristics of precipitates were evaluated by a transmission electron microscope(TEM),and the precipitation strengthening mechanism was discussed.The results reveal that the strengthening is mainly contributed by the precipitation ofβ″phase after two-stage aging,and the number density and size of the precipitates are significantly depended on the pre-aging time.The number density of precipitates is increased with the pre-aging time prolonged from 0 h to 4 h,and then decreases with the further increase of pre-aging time from 4 h to 6 h.The precipitates with the highest density and smallest size are observed after pre-aging for 4 h.After pre-aged at 100℃for 4 h and then artificial aged at 200℃for 30 min,the yield strength of 207 MPa,ultimate tensile strength of 325 MPa and elongation of 7.6%are achieved.
基金National Natural Science Foundation of China No.51905068Natural Science Foundation of Liaoning Province No.2020-HYLH-24The open research fund from the State Key Laboratory of Rolling and Automation,Northeastern University No.2020RALKFKT012。
文摘Magnesium alloy is one of the lightest metal structural materials.The weight is further reduced through the hollow structure.However,the hollow structure is easily damaged during processing.In order to maintain the hollow structure and to transfer the stresses during the high temperature deformation,the sand mandrel is proposed.In this paper,the hollow AZ31 magnesium alloy three-channel joint is studied by hot extrusion forming.Sand as one of solid granule medium is used to fill the hollow magnesium alloy.The extrusion temperatures are 230℃ and 300℃,respectively.The process parameters(die angle,temperature,bottom thickness,sidewall thickness,edge-to-middle ratio in bottom,bottom shape)of the hollow magnesium alloy are analyzed based on the results of experiments and the finite element method.The results are shown that the formability of the hollow magnesium alloy will be much better when the ratio of sidewall thickness to the bottom thickness is 1:1.5.Also when edge-to-middle ratio in bottom is about 1:1.5,a better forming product can be received.The best bottom shape in these experiments will be convex based on the forming results.The grain will be refined obviously after the extrusion.Also the microstructures will be shown as streamlines.And these lines will be well agreement with the mold in the corner.
基金Key R&D Plan Projects in Hubei Province(Grant No.2021BID001)the Research on Multiple Regression and Fitting Technology of Simulation Data for Dynamic Umbrella Opening of Lifesaving Umbrella(Grant No.HX2021157)。
文摘In the process of riveting an MB15 forging die,cracks were discovered emerging along the longitudinal direction and near the riveting hole.Through fracture analysis,microscopic observation,energy spectrum analysis,metallographic examination,and hardness test,the properties and causes of the cracks are discussed.The results indicate that the cracking type is intergranular brittle cracking,occurring during the forging stage.Furthermore,the recrystallization at the crack site is found to be incomplete,which is attributed to the low deformation temperature.
文摘语义构建离不开认知识解因素。die of和die from可以与同样的表达式搭配,即die of X和die from X。就规约意义而言,die of X通常表达客观的、直接的原因,而die from X通常表达客观的、间接的原因。但在die of X和die from X语义构建过程中,通过认知识解,客观的、直接的原因会被识解为主观的、间接原因,客观的、间接的原因会被构建为主观的、直接的原因。
文摘Aluminum high pressure die casting(HPDC)technology has evolved in the past decades,enabling stronger and larger one-piece casting with significant part consolidation.It also offers a higher design freedom for more mass-efficient thin-walled body structures.For body structures that require excellent ductility and fracture toughness to be joined with steel sheet via self-piercing riveting(for instance,shock towers and hinge pillars,etc.),a costly T7 heat treatment comprising a solution heat treatment at elevated temperatures(450℃-500℃)followed by an over-ageing heat treatment is needed to optimize microstructure for meeting product requirement.To enable cost-efficient mass production of HPDC body structures,it is important to eliminate the expensive T7 heat treatment without sacrificing mechanical properties.Optimizing die cast alloy chemistry is a potential solution to improve fracture toughness and ductility of the HPDC components.The present study intends to tailor the Mg and Cu additions for a new Al-Si-Cr type die casting alloy(registered as A379 with The Aluminum Association,USA)to achieve the desired tensile properties without using T7 heat treatment.It was found that Cu addition should be avoided,as it is not effective in enhancing strength while degrades tensile ductility.Mg addition is very effective in improving strength and has minor impact on tensile ductility.The investigated Al-Si-Cr alloy with a nominal composition of Al-8.5wt.%Si-0.3wt.%Cr-0.2wt.%Fe shows comparable tensile properties with the T7 treated AlSi10MnMg alloy which is currently used for manufacturing shock towers and hinge pillars.
文摘The integrated circuit (IC) manufacturing process is capital intensive and complex. The production process of unit product (or die, as it is commonly referred to) takes several weeks. Semiconductor factories (fabs) continuously attempt to improve their productivity, as measured in output and cycle time (or mean flow time). The conflicting objective of producing maximum units at minimal production cycle time and at the highest quality, as measured by die yield, is discussed in this paper. The inter-related effects are characterized, and a model is proposed to address this multi-objective function. We then show that, with this model, die cost can be optimized for any given operating conditions of a fab. A numerical example is provided to illustrate the practicality of the model and the proposed optimization method.
文摘在菲律宾发现的各种海龟都濒临灭绝。但是现在,许多过去收集海龟蛋吃或卖的人都在努力保护海龟的安全。All the kinds of sea turtles found in the Philippines are endangered.That means they are at risk of dying out.But now,the turtles have one less threat.Many people who used to collect their eggs to eat or to sell are now working to keep turtles safe.
文摘狗是非常忠诚的伙伴。即使一生中可能会有很多主人,它们也不会真正忘记自己的第一个主人。Jolie Mejía recently witnessed an undying devotion first hand while on a family trip to the beach.She was enjoying surfing in the district of Punta Negra in Lima,Peru when she noticed a stray dog gazing longingly out at the sea.
