The effect of Si content on the microstructures and growth kinetics of intermetallic compounds(IMCs)formed during the initial interfacial reaction(<10 s)between solid steel and liquid aluminum was investigated by a...The effect of Si content on the microstructures and growth kinetics of intermetallic compounds(IMCs)formed during the initial interfacial reaction(<10 s)between solid steel and liquid aluminum was investigated by a thermophysical simulation method.The influence of Si addition on interfacial mechanical properties was revealed by a high-frequency induction brazing.The results showed that IMCs layers mainly consisted ofη-Fe_(2)Al_(5)andθ-Fe_(4)Al_(13).The addition of Si reduced the thickness of the IMCs layer.The growth of theηphase was governed by the diffusion process when adding 2 wt.%Si to the aluminum melt.When 5 wt.%or 8 wt.%Si was added to aluminum,the growth was governed by both the diffusion process and interfacial reaction,and ternary phaseτ1/τ9-(Al,Si)_(5)Fe_(3)was formed in theηphase.The apparent activation energies of theηphase decreased gradually with increasing Si content.The joint with pure aluminum metal had the highest tensile strength and impact energy.展开更多
The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H...The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.展开更多
Implementing high-performance silicon(Si)anode in actual processing and application is highly desirable for next-generation,high-energy Li-ion batteries.However,high content of inactive matrix(including conductive age...Implementing high-performance silicon(Si)anode in actual processing and application is highly desirable for next-generation,high-energy Li-ion batteries.However,high content of inactive matrix(including conductive agent and binder)is often indispensable in order to ensure local conductivity and suppress pulverization tendency of Si particles,which thus cause great capacity loss based on the mass of whole electrode.Here,we designed an accordion-structured,high-performance electrode with high Si content up to 95%.Si nanoparticles were well anchored into the interlayer spacings of accordion-like graphene arrays,and free-standing electrode was prepared via a simple filtration process without any binder.Conductive accordion framework ensures strong confinement effect of Si nanoparticles and also provides direct,non-tortuous channels for fast electrochemical reaction kinetics.As a consequence,the accordion Si electrodes exhibit ultrahigh,electrode-based capacities up to 3149 mAh g^(-1)(under Si content of 91%),as well as long-term stability.Also,the accordion electrode can bear extreme condition of over-lithiation and maintains stable in full-cell test.This design provides a significant stride in high Si content toward realistic,high-performance electrodes.展开更多
Hot-rolled Fe-（0.75-2.20）Si （mass%） alloys were oxidized in dry air at 600-1200 ℃. The oxidation process was carried out by thermal gravimetric analysis （TGA）. At 600- 1 150 ℃, oxidation gain curves were appro...Hot-rolled Fe-（0.75-2.20）Si （mass%） alloys were oxidized in dry air at 600-1200 ℃. The oxidation process was carried out by thermal gravimetric analysis （TGA）. At 600- 1 150 ℃, oxidation gain curves were approximately parabolic. Electron probe mieroanalysis （EPMA） was applied to investigate cross-section morphology of oxide layer and element distribution across the layer. At lower temperature of 700 ℃, the oxide layer consisted of internal oxidation zone （IOZ）, inner Si-rich layer （conglomerate of fayalite and magnetite） and outer hematite layer, while at higher temperature of 1200 ℃, fayalite and wustite were observed in external oxide scale. Liquidus temperature of fayalite was detected by differential scanning calorimetry （DSC）. Through comparing the oxidation mass gain and parabolic rate constant of the alloys, it was found that oxidation resistance of Fe-Si alloy was enhanced by increasing Si content below 1 150 ℃ while increasing Si content of the alloy resulted in higher oxidation rate above 1150 ℃ owing to the liquid fayalite formation.展开更多
Continuous cooling transformation behaviors of low carbon steels with two Si contents （0. 50% and 1. 35%） were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling ...Continuous cooling transformation behaviors of low carbon steels with two Si contents （0. 50% and 1. 35%） were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature （Ar3）, phase microstructures, and hardness were studied. The results show that, in the ease of the deformation with the true strain of 0. 4, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on At3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.展开更多
To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace(LF)refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing,the effects of ferrosilicon al...To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace(LF)refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing,the effects of ferrosilicon alloy,Si content of steel,and slag basicity on the compositions of inclusions during LF refining were investigated in Al-killed steel.Al2O3 inclusions could be transformed into CaO-Al2O3-MgO-CaS inclusions after adding ferrosilicon alloy in the LF refining process as this alloy contains some CaSi alloy impurities.The addition of all ferrosilicon alloys required for the steel in the tapping process could eliminate the influence of Ca in ferrosilicon alloy on the compositions of inclusions.Si in liquid steel had a significant influence on the compositions of inclusions during LF refining when CaO-Al2O3-SiO2-MgO slag with high basicity of 7.0 was used.This was because[Ca]produced by the reaction of CaO and[Al]could be consumed more readily by SiO2 in Si-free steel than in Si-containing steel,which was confirmed by the difference of total calcium content between Si-free and Si-containing steels.As a result,Al2O3 and MgO·Al2O3 inclusions were retained in Si-free steel,whereas calcium aluminate inclusions were found in Si-containing steel.For CaO-Al2O3-SiO2-MgO slag with low basicity of 2.8,Al2O3 and MgO·Al2O3 inclusions were obtained after LF refining in Si-containing steel when all ferrosilicon alloys required for the steel were added in the tapping process.This was because the reaction of CaO and[Al]was weak,and residual[Ca]in the steel could be rapidly consumed by SiO2 in low-basicity slag owing to the low activity of CaO and high activity of SiO2,leading to a low total calcium content of 0.0003%in Si-containing steel.展开更多
In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically...In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically.The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer(MRL),whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites,while the hypereutectic Al-Si/AZ91D composites were opposite.The MRL included eutectic layer(E layer),intermetallic compound layer(IMC layer)and transition region layer(T layer).In the IMC layer,the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg_(2)Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides,increasing Si content,the thickness proportion of the T layer increased,forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content,and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa,which was 73.4% higher than the Al-6Si/AZ91D composite.The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content.The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg_(2)Si particle reinforcement,the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.展开更多
By means of scanning electron microscopy(SEM), energy dispersive spectrum(EDS), X-ray diffractometry(XRD) and metallographic analysis, the effects of variation of magnesium content on phase constituents of Al-Mg-Si-Cu...By means of scanning electron microscopy(SEM), energy dispersive spectrum(EDS), X-ray diffractometry(XRD) and metallographic analysis, the effects of variation of magnesium content on phase constituents of Al-Mg-Si-Cu alloys were investigated. The results indicate that the constituents formed during casting alloys are main Al1.9CuMg4.1Si3.3,Al4(MnFe)3Si2 and Mg2Si, while pure Si is only present in the alloy containing lower magnesium content. Increasing Mg content leads to increasing the amount of Mg2Si, but decreasing the amount of Al1.9CuMg4.1Si3.3 and Al4(MnFe)3Si2. During the following homogenization process, Al1.9CuMg4.1Si3.3 is completely dissolved, Al4(MnFe)3Si2 and pure Si remain unchanged. After rolling and final heat treatment, the constituents in the alloys change no longer.展开更多
The oxidizing behavior of Si-containing steel was investigated in an O2 and N2 binary-component gas with oxygen contents ranging between 0.5 vol% and 4.0 vol% under anisothermal-oxidation conditions. A simultaneous th...The oxidizing behavior of Si-containing steel was investigated in an O2 and N2 binary-component gas with oxygen contents ranging between 0.5 vol% and 4.0 vol% under anisothermal-oxidation conditions. A simultaneous thermal analyzer was employed to simulate the heating process of Si-containing steel in industrial reheating furnaces. The oxidation gas mixtures were introduced from the commencement of heating. The results show that the oxidizing rate remains constant in the isothermal holding process at high temperatures; therefore, the mass change versus time presents a linear law. A linear relation also exists between the oxidizing rate and the oxygen content. Using the linear regression equation, the oxidation rate at different oxygen contents can be predicted. In addition, the relationship between the total mass gain and the oxygen content is linear; thus, the total mass gain at oxygen contents between 0.5 vol%–4.0 vol% can be determined. These results enrich the theoretical studies of the oxidation process in Si-containing steels.展开更多
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.51875037)the Beijing Municipal Natural Science Foundation,China(No.3192021)the Fundamental Research Funds for the Central Universities,China(No.FRF-GF-18-004B).
文摘The effect of Si content on the microstructures and growth kinetics of intermetallic compounds(IMCs)formed during the initial interfacial reaction(<10 s)between solid steel and liquid aluminum was investigated by a thermophysical simulation method.The influence of Si addition on interfacial mechanical properties was revealed by a high-frequency induction brazing.The results showed that IMCs layers mainly consisted ofη-Fe_(2)Al_(5)andθ-Fe_(4)Al_(13).The addition of Si reduced the thickness of the IMCs layer.The growth of theηphase was governed by the diffusion process when adding 2 wt.%Si to the aluminum melt.When 5 wt.%or 8 wt.%Si was added to aluminum,the growth was governed by both the diffusion process and interfacial reaction,and ternary phaseτ1/τ9-(Al,Si)_(5)Fe_(3)was formed in theηphase.The apparent activation energies of theηphase decreased gradually with increasing Si content.The joint with pure aluminum metal had the highest tensile strength and impact energy.
基金Project(2011KJZD04)supported by the CHINALCO Science and Development Foundation,China
文摘The correlation between Si content （0.1%-0.5%, mass fraction） and pulse laser welding performance of AI-Mn-Mg aluminum alloy sheets was studied. The sheets were fabricated in the laboratory, with gauge of 0.45 mm, H16 temper by pulse laser welding. It was found that no cracking existed in the welding pool as Si content was below 0.34%. However, when the Si content increased to 0.47%, cracking formed in the welding pool. Microstructure observations indicated that residual eutectic phases distributed at the grain boundaries were discontinuous and appeared to be small particles in lower Si content alloys; the residual eutectic phases distributed at the grain boundaries were partially continuous and appeared to be films in higher Si content alloys. These phenomena could explain why Si content adversely affected the laser welding performance.
基金supported by Shaanxi Yanchang Petroleum Co.,Ltd.(18529)Yiwu Research Institute of Fudan University(21557)+1 种基金the National Science Foundation of China(22075048)the Shanghai International Collaboration Research Project(19520713900).
文摘Implementing high-performance silicon(Si)anode in actual processing and application is highly desirable for next-generation,high-energy Li-ion batteries.However,high content of inactive matrix(including conductive agent and binder)is often indispensable in order to ensure local conductivity and suppress pulverization tendency of Si particles,which thus cause great capacity loss based on the mass of whole electrode.Here,we designed an accordion-structured,high-performance electrode with high Si content up to 95%.Si nanoparticles were well anchored into the interlayer spacings of accordion-like graphene arrays,and free-standing electrode was prepared via a simple filtration process without any binder.Conductive accordion framework ensures strong confinement effect of Si nanoparticles and also provides direct,non-tortuous channels for fast electrochemical reaction kinetics.As a consequence,the accordion Si electrodes exhibit ultrahigh,electrode-based capacities up to 3149 mAh g^(-1)(under Si content of 91%),as well as long-term stability.Also,the accordion electrode can bear extreme condition of over-lithiation and maintains stable in full-cell test.This design provides a significant stride in high Si content toward realistic,high-performance electrodes.
基金Item Sponsored by National High-tech Research and Development Program of China(2011BAE13B04)National Natural Science Foundation of China(51204047,51204053)
文摘Hot-rolled Fe-（0.75-2.20）Si （mass%） alloys were oxidized in dry air at 600-1200 ℃. The oxidation process was carried out by thermal gravimetric analysis （TGA）. At 600- 1 150 ℃, oxidation gain curves were approximately parabolic. Electron probe mieroanalysis （EPMA） was applied to investigate cross-section morphology of oxide layer and element distribution across the layer. At lower temperature of 700 ℃, the oxide layer consisted of internal oxidation zone （IOZ）, inner Si-rich layer （conglomerate of fayalite and magnetite） and outer hematite layer, while at higher temperature of 1200 ℃, fayalite and wustite were observed in external oxide scale. Liquidus temperature of fayalite was detected by differential scanning calorimetry （DSC）. Through comparing the oxidation mass gain and parabolic rate constant of the alloys, it was found that oxidation resistance of Fe-Si alloy was enhanced by increasing Si content below 1 150 ℃ while increasing Si content of the alloy resulted in higher oxidation rate above 1150 ℃ owing to the liquid fayalite formation.
基金Item Sponsored by National Natural Science Foundation of China (50527402)
文摘Continuous cooling transformation behaviors of low carbon steels with two Si contents （0. 50% and 1. 35%） were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature （Ar3）, phase microstructures, and hardness were studied. The results show that, in the ease of the deformation with the true strain of 0. 4, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on At3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.
文摘To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace(LF)refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing,the effects of ferrosilicon alloy,Si content of steel,and slag basicity on the compositions of inclusions during LF refining were investigated in Al-killed steel.Al2O3 inclusions could be transformed into CaO-Al2O3-MgO-CaS inclusions after adding ferrosilicon alloy in the LF refining process as this alloy contains some CaSi alloy impurities.The addition of all ferrosilicon alloys required for the steel in the tapping process could eliminate the influence of Ca in ferrosilicon alloy on the compositions of inclusions.Si in liquid steel had a significant influence on the compositions of inclusions during LF refining when CaO-Al2O3-SiO2-MgO slag with high basicity of 7.0 was used.This was because[Ca]produced by the reaction of CaO and[Al]could be consumed more readily by SiO2 in Si-free steel than in Si-containing steel,which was confirmed by the difference of total calcium content between Si-free and Si-containing steels.As a result,Al2O3 and MgO·Al2O3 inclusions were retained in Si-free steel,whereas calcium aluminate inclusions were found in Si-containing steel.For CaO-Al2O3-SiO2-MgO slag with low basicity of 2.8,Al2O3 and MgO·Al2O3 inclusions were obtained after LF refining in Si-containing steel when all ferrosilicon alloys required for the steel were added in the tapping process.This was because the reaction of CaO and[Al]was weak,and residual[Ca]in the steel could be rapidly consumed by SiO2 in low-basicity slag owing to the low activity of CaO and high activity of SiO2,leading to a low total calcium content of 0.0003%in Si-containing steel.
基金the supports provided by the National Natural Science Foundation of China(Nos.52075198 and 52271102)the China Postdoctoral Science Foundation(No.2021M691112)+1 种基金the State Key Lab of Advanced Metals and Materials(No.2021-ZD07)the Analytical and Testing Center,HUST。
文摘In this paper,the effect of the Si content on microstructure evolution,mechanical properties,and fracture behavior of the Al-xSi/AZ91D bimetallic composites prepared by compound casting was investigated systematically.The obtained results showed that all the Al-xSi/AZ91D bimetallic composites had a metallurgical reaction layer(MRL),whose thickness increased with increasing Si content for the hypoeutectic Al-Si/AZ91D composites,while the hypereutectic Al-Si/AZ91D composites were opposite.The MRL included eutectic layer(E layer),intermetallic compound layer(IMC layer)and transition region layer(T layer).In the IMC layer,the hypereutectic Al-Si/AZ91D composites contained some Si solid solution and flocculent Mg_(2)Si+Al-Mg IMCs phases not presented in the hypoeutectic Al-Si/AZ91D composites.Besides,increasing Si content,the thickness proportion of the T layer increased,forming an inconsistent preferred orientation of the MRL.The shear strengths of the Al-xSi/AZ91D bimetallic composites enhanced with increasing Si content,and the Al-15Si/AZ91D composite obtained a maximum shear strength of 58.6 MPa,which was 73.4% higher than the Al-6Si/AZ91D composite.The fractures of the Al-xSi/AZ91D bimetallic composites transformed from the T layer into the E layer with the increase of the Si content.The improvement of the shear strength of the Al-xSi/AZ91D bimetallic composites was attributed to the synergistic action of the Mg_(2)Si particle reinforcement,the reduction of oxidizing inclusions and the ratio of Al-Mg IMCs as well as the orientation change of the MRL.
基金Project(2002AA331050) supported by Hi-tech Research and Development Program of China project(0208) supported by Science and Technology Research of Ministry of Education of China
文摘By means of scanning electron microscopy(SEM), energy dispersive spectrum(EDS), X-ray diffractometry(XRD) and metallographic analysis, the effects of variation of magnesium content on phase constituents of Al-Mg-Si-Cu alloys were investigated. The results indicate that the constituents formed during casting alloys are main Al1.9CuMg4.1Si3.3,Al4(MnFe)3Si2 and Mg2Si, while pure Si is only present in the alloy containing lower magnesium content. Increasing Mg content leads to increasing the amount of Mg2Si, but decreasing the amount of Al1.9CuMg4.1Si3.3 and Al4(MnFe)3Si2. During the following homogenization process, Al1.9CuMg4.1Si3.3 is completely dissolved, Al4(MnFe)3Si2 and pure Si remain unchanged. After rolling and final heat treatment, the constituents in the alloys change no longer.
基金financially supported by the National Natural Science Foundation of China(No.51274154)The Major Projects of Technology Innovation of Hubei Province,China(No.2017AAA116)the Special Fund of Wuhan University of Science and Technology for Master Student’s Short-Term Studying Abroad
文摘The oxidizing behavior of Si-containing steel was investigated in an O2 and N2 binary-component gas with oxygen contents ranging between 0.5 vol% and 4.0 vol% under anisothermal-oxidation conditions. A simultaneous thermal analyzer was employed to simulate the heating process of Si-containing steel in industrial reheating furnaces. The oxidation gas mixtures were introduced from the commencement of heating. The results show that the oxidizing rate remains constant in the isothermal holding process at high temperatures; therefore, the mass change versus time presents a linear law. A linear relation also exists between the oxidizing rate and the oxygen content. Using the linear regression equation, the oxidation rate at different oxygen contents can be predicted. In addition, the relationship between the total mass gain and the oxygen content is linear; thus, the total mass gain at oxygen contents between 0.5 vol%–4.0 vol% can be determined. These results enrich the theoretical studies of the oxidation process in Si-containing steels.
