The influence of high pressure and manganese addition on Fe-rich phases(FRPs)and mechanical properties of Al-14Si-2Fe alloy with rheo-squeeze casting(RSC)was investigated.The semi-solid alloy melt was treated by ultra...The influence of high pressure and manganese addition on Fe-rich phases(FRPs)and mechanical properties of Al-14Si-2Fe alloy with rheo-squeeze casting(RSC)was investigated.The semi-solid alloy melt was treated by ultrasonic vibration(UV)firstly,and then formed by squeeze casting(SC).Results show that the FRPs in as-cast SC alloys are composed of coarseβ-Al5(Fe,Mn)Si,δ-Al4(Fe,Mn)Si2 and bone-shapedα-Al15(Fe,Mn)3Si2 phases when the pressure is 0 MPa.With RSC process,the FRPs are first refined by UV,and then the solidification under pressure further causes the grains to become smaller.The peritectic transformation occurs during the formation ofαphase.For the alloy with the same composition,the ultimate tensile strength(UTS)of RSC sample is higher than that of the SC sample.With the same forming process,the UTS of Al-14Si-2Fe-0.8Mn alloy is higher than that of Al-14Si-2Fe-0.4Mn alloy.展开更多
The effect of squeeze casting on microstructure and mechanical properties of hypereutectic Al-xS i alloys（x = 15, 17.5, 22 wt%） was investigated in this study. Results show that microstructure of the hypereutectic A...The effect of squeeze casting on microstructure and mechanical properties of hypereutectic Al-xS i alloys（x = 15, 17.5, 22 wt%） was investigated in this study. Results show that microstructure of the hypereutectic Al-x Si alloys was obviously improved by squeeze casting. The amount of coarse primary Si phase decreased, while that of fine primary α-Al dendrites increased with the increase of squeeze casting pressure. Due to the decrease of coarse primary Si particles, cracking of the matrix was reduced, whilst the fine microstructure, and mechanical properties of the squeeze casting alloys were improved. Compared with gravity casting alloys, mechanical properties of the hypereutectic Al-xS i alloys solidified at 600 MPa were improved significantly. Hardness of the squeeze casting hypereutectic Al-（15, 17.5, 22 wt%） Si alloys was improved by 15.91%, 12.23%, 17.48%, ultimate tensile strength was improved by 37.85%, 32.27%, 22.74%,and elongation was improved by 55.83%, 167.86%, 126.76%, respectively. Due to the uniform distribution of Si phases in squeeze casting Al-x Si alloys, their wear resistance was markedly enhanced.展开更多
The effect of the melt holding temperature on the morphological evolution and sedimentation behavior of iron-rich intermetallics in Al-7.0 Si-1.0 Fe-1.2 Mn-0.25 Mg alloy was investigated using an optical microscope,sc...The effect of the melt holding temperature on the morphological evolution and sedimentation behavior of iron-rich intermetallics in Al-7.0 Si-1.0 Fe-1.2 Mn-0.25 Mg alloy was investigated using an optical microscope,scanning electron microscope and differential thermal analyzer.The results show that as the holding temperature decreases,the morphologies of the primary iron-rich phase in matrix change from star-like to polygonal,and the number of the primary phases gradually decreases and disappears at 615°C.Finally,the Chinese script phases with small size,high compact and uniform distribution are obtained.In contrast,the primary iron-rich phases in slag transform into a coarser polygonal shape with lower roundness,and some of them have hollow structures.Furthermore,the area fraction of intermetallics and Fe content in the matrix decrease gradually due to the formation and growth of sludge and subsequent natural sedimentation during melt holding.With the decrease of holding temperature,the main factors hindering the settlement of the primary phases are morphology,size,and density in turn.展开更多
The influences of different Zr/Sc ratios on the microstructural evolution and mechanical performances of Al-2 Si alloy were investigated in this paper.The as-cast samples were characterized and analyzed by the scannin...The influences of different Zr/Sc ratios on the microstructural evolution and mechanical performances of Al-2 Si alloy were investigated in this paper.The as-cast samples were characterized and analyzed by the scanning electron microscope(SEM)with an energy dispersive spectrometer(EDS)to indicate the refining effect of the different Zr/Sc ratios on theα-Al and Si phases in Al-2 Si alloy.The results indicate that theα-Al phases are refined from coarse dendritic structure to relatively fine equiaxed grains when the Zr/Sc ratio is equal to 1:1.Meanwhile,the eutectic Si phase in Al-2 Si-0.2 Zr-0.2 Sc alloy is modified from the coarse plate and needle to fine fiber and partial granular structure,and the average roundness of eutectic Si is decreased by 75%from 16 to 4.With the refinement ofα-Al phases and the modification of eutectic Si structure,the ultimate tensile strength(UTS)is improved by 53%and the elongation(EL)is increased by 64%when the Zr/Sc ratio is equal to 1:1.In addition,the UTS decreases and EL is enhanced with the increase of tensile temperature.Moreover,the fracture model of Al-2 Si-0.2 Zr-0.2 Sc alloy in250℃changes into the ductile fracture.展开更多
Calcium-Silicate-Hydrate-phases (CSH-phases) are important binding agents of building materials. The synthesis of CSH phases and their structural characterization was done to investigate the crystallization in depende...Calcium-Silicate-Hydrate-phases (CSH-phases) are important binding agents of building materials. The synthesis of CSH phases and their structural characterization was done to investigate the crystallization in dependence of an increasing CaO/SiO2 ratio (C/S ratios) from 0.41 up to 1.66 at temperatures in the crossover region of tobermorite to xonotlite (180℃ and 230℃). Parallel runs with the same C/S ratio but on the one hand with constant mass of quartz and variation of lime and on the other hand under reverse conditions (constant mass of lime but variable amounts of quartz) were performed at both temperatures. The aim was to clarify the connections of crystallization mechanism and kinetics of phase formation with structure, crystallinity and morphology of the CSH’s in the mentioned C/S ratio for both temperatures in the tobermorite-xonotlite crossover region. The parallel experiments with different mass ratios of the educts are important to study the influence of time evaluation of supersaturation within the solution under the peculiarities of the retrograde solubility of lime but accelerated solubility of quartz. The products were characterized by XRD, SEM/EDX, FTIR and 29Si MAS NMR spectroscopy (using the Q-site nomenclature [1]). The experiments could clarify some important connections of crystallization process and the reaction pathway.展开更多
An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characteriz...An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characterized via electron back-scattered diffraction,transmission Kikuchi diffraction and scanning transmission electron microscopy.From the tail of the gage to the necking region,the microstructure of the material evolved from low-angle grain boundaries(LAGB s) to mixtures of LAGBs and high-angle grain boundaries(HAGBs),and fine equiaxed recrystallized grains.The elongation to failure in the tensile test exceeds 167%.During the hot deformation,continuous dynamic recrystallization of the austenitic matrix was promoted by the multiple secondary phases.The dislocations introduced by the secondary phases were rearranged and continuously transformed into HAGBs.The initially coarse grains(30.5 μm) were refined into ultra-fine equiaxed grains(1 μm),which contributed significantly the enhanced plasticity during hot deformation of the steel.In the necking area of the sample,twins were nucleated in the stress concentration regions and accommodated the local strain by discontinuous dynamic recrystallization,which was also beneficial to improving the plasticity.展开更多
Analysis of the Si and AI phases in coal gangue fuel and its ash is important for use of coal gangue ashes. A comprehensive study by theoretical and experimental analyses with differential thermal analysis, X-ray diff...Analysis of the Si and AI phases in coal gangue fuel and its ash is important for use of coal gangue ashes. A comprehensive study by theoretical and experimental analyses with differential thermal analysis, X-ray diffraction and Infrared Spectroscopy has been made in the present article to explore the diagram of the Si and Al phases in coal gangue fuel and its ashes. It is found that kaolinite and quartz are the main phases in coal gangue fuel. The ratio of moles A1203 to SiO2 （i.e., Al2O3 （mole） / SiO2 （mole）） is usually no more than 0.5 in most coal gangue fuel and its ashes. The kaolinit at about 984℃ releases a large quantity of SiO2, which makes calcine coal gangue more active than coal gangue itself. The relationship between the ratio A1203 （mole）]SiO2（mole）and the components of coal gangue ash is analyzed, resulting in a formula to calculate the quantity of each phase. Applying the formula to the testing samples from an electric plant in north China supports the above conclusions.展开更多
The effect of cerium(Ce)addition on the eutectic Si,β-Al_5Fe Si phase,and the tensile properties of A380 alloy specimens prepared by squeeze-casting were studied by optical microscopy(OM),scanning electron microscopy...The effect of cerium(Ce)addition on the eutectic Si,β-Al_5Fe Si phase,and the tensile properties of A380 alloy specimens prepared by squeeze-casting were studied by optical microscopy(OM),scanning electron microscopy(SEM),and X-ray diffraction(XRD).The experimental results showed that Ce more effectively modified the eutectic Si and refined theβ-Al_5Fe Si.The refinement effect significantly increased under a specific pressure of 100 MPa with the addition of Ce from 0.1wt%to 0.9wt%.In contrast,the average length and the aspect ratio of the eutectic Si andβ-Al_5Fe Si exhibited their optimal values when the content of the added Ce was greater than 0.5wt%.Needle-like Al_8Cu_4Ce was precipitated with the addition of excessive Ce;hence,the mechanical properties of A380 gradually decreased with increasing Ce content in the range from 0.3wt%to 0.9wt%.展开更多
基金Project(51605342) supported by the National Natural Science Foundation of ChinaProject(2015CFB431) supported by the Natural Science Foundation of Hubei Province,China+1 种基金Project(K201520) supported by the Science Research Foundation of Wuhan Institute of Technology,ChinaProject(2016KA01) supported by the Open Research Fund Program of Hubei Provincial Key Laboratory of Chemical Equipment Intensification and Intrinsic Safety,China
文摘The influence of high pressure and manganese addition on Fe-rich phases(FRPs)and mechanical properties of Al-14Si-2Fe alloy with rheo-squeeze casting(RSC)was investigated.The semi-solid alloy melt was treated by ultrasonic vibration(UV)firstly,and then formed by squeeze casting(SC).Results show that the FRPs in as-cast SC alloys are composed of coarseβ-Al5(Fe,Mn)Si,δ-Al4(Fe,Mn)Si2 and bone-shapedα-Al15(Fe,Mn)3Si2 phases when the pressure is 0 MPa.With RSC process,the FRPs are first refined by UV,and then the solidification under pressure further causes the grains to become smaller.The peritectic transformation occurs during the formation ofαphase.For the alloy with the same composition,the ultimate tensile strength(UTS)of RSC sample is higher than that of the SC sample.With the same forming process,the UTS of Al-14Si-2Fe-0.8Mn alloy is higher than that of Al-14Si-2Fe-0.4Mn alloy.
基金support from the National Natural Science Foundation of China(Grant No.51674168)Shenyang Application Basic Research Fund(Grant No.F14-231-1-23)
文摘The effect of squeeze casting on microstructure and mechanical properties of hypereutectic Al-xS i alloys（x = 15, 17.5, 22 wt%） was investigated in this study. Results show that microstructure of the hypereutectic Al-x Si alloys was obviously improved by squeeze casting. The amount of coarse primary Si phase decreased, while that of fine primary α-Al dendrites increased with the increase of squeeze casting pressure. Due to the decrease of coarse primary Si particles, cracking of the matrix was reduced, whilst the fine microstructure, and mechanical properties of the squeeze casting alloys were improved. Compared with gravity casting alloys, mechanical properties of the hypereutectic Al-xS i alloys solidified at 600 MPa were improved significantly. Hardness of the squeeze casting hypereutectic Al-（15, 17.5, 22 wt%） Si alloys was improved by 15.91%, 12.23%, 17.48%, ultimate tensile strength was improved by 37.85%, 32.27%, 22.74%,and elongation was improved by 55.83%, 167.86%, 126.76%, respectively. Due to the uniform distribution of Si phases in squeeze casting Al-x Si alloys, their wear resistance was markedly enhanced.
基金Project(2017GDASCX-0117)supported by the Guangdong Academy of Sciences,ChinaProject(201806010126)supported by the Pearl River S&T Nova Program of Guangzhou,China+3 种基金Projects(2017A050503004,2017A07071029)supported by the Guangdong Provincial Program of Science and Technology,ChinaProject(18126010)supported by the Guangxi Autonomous Regional Program of Science and Technology,ChinaProject(201802030012)supported by the Guangzhou Municipal Science and Technology Bureau,ChinaProject(2017A0109005)supported by the Sihui Plan Project of Science and Technology,China.
文摘The effect of the melt holding temperature on the morphological evolution and sedimentation behavior of iron-rich intermetallics in Al-7.0 Si-1.0 Fe-1.2 Mn-0.25 Mg alloy was investigated using an optical microscope,scanning electron microscope and differential thermal analyzer.The results show that as the holding temperature decreases,the morphologies of the primary iron-rich phase in matrix change from star-like to polygonal,and the number of the primary phases gradually decreases and disappears at 615°C.Finally,the Chinese script phases with small size,high compact and uniform distribution are obtained.In contrast,the primary iron-rich phases in slag transform into a coarser polygonal shape with lower roundness,and some of them have hollow structures.Furthermore,the area fraction of intermetallics and Fe content in the matrix decrease gradually due to the formation and growth of sludge and subsequent natural sedimentation during melt holding.With the decrease of holding temperature,the main factors hindering the settlement of the primary phases are morphology,size,and density in turn.
基金Project supported by the National Natural Science Foundation of China(51561021),ChinaThe State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals+1 种基金Lanzhou University of Technology(SKLAB02019007),ChinaTraining Program on College Students of Gansu Province(DC2019161),China。
文摘The influences of different Zr/Sc ratios on the microstructural evolution and mechanical performances of Al-2 Si alloy were investigated in this paper.The as-cast samples were characterized and analyzed by the scanning electron microscope(SEM)with an energy dispersive spectrometer(EDS)to indicate the refining effect of the different Zr/Sc ratios on theα-Al and Si phases in Al-2 Si alloy.The results indicate that theα-Al phases are refined from coarse dendritic structure to relatively fine equiaxed grains when the Zr/Sc ratio is equal to 1:1.Meanwhile,the eutectic Si phase in Al-2 Si-0.2 Zr-0.2 Sc alloy is modified from the coarse plate and needle to fine fiber and partial granular structure,and the average roundness of eutectic Si is decreased by 75%from 16 to 4.With the refinement ofα-Al phases and the modification of eutectic Si structure,the ultimate tensile strength(UTS)is improved by 53%and the elongation(EL)is increased by 64%when the Zr/Sc ratio is equal to 1:1.In addition,the UTS decreases and EL is enhanced with the increase of tensile temperature.Moreover,the fracture model of Al-2 Si-0.2 Zr-0.2 Sc alloy in250℃changes into the ductile fracture.
文摘Calcium-Silicate-Hydrate-phases (CSH-phases) are important binding agents of building materials. The synthesis of CSH phases and their structural characterization was done to investigate the crystallization in dependence of an increasing CaO/SiO2 ratio (C/S ratios) from 0.41 up to 1.66 at temperatures in the crossover region of tobermorite to xonotlite (180℃ and 230℃). Parallel runs with the same C/S ratio but on the one hand with constant mass of quartz and variation of lime and on the other hand under reverse conditions (constant mass of lime but variable amounts of quartz) were performed at both temperatures. The aim was to clarify the connections of crystallization mechanism and kinetics of phase formation with structure, crystallinity and morphology of the CSH’s in the mentioned C/S ratio for both temperatures in the tobermorite-xonotlite crossover region. The parallel experiments with different mass ratios of the educts are important to study the influence of time evaluation of supersaturation within the solution under the peculiarities of the retrograde solubility of lime but accelerated solubility of quartz. The products were characterized by XRD, SEM/EDX, FTIR and 29Si MAS NMR spectroscopy (using the Q-site nomenclature [1]). The experiments could clarify some important connections of crystallization process and the reaction pathway.
文摘An austenitic stainless steel with 6 wt% Si and multiple secondary phases was produced with the aim to achieve enhanced plasticity during hot deformation.The micro structure of the steel after fracture was characterized via electron back-scattered diffraction,transmission Kikuchi diffraction and scanning transmission electron microscopy.From the tail of the gage to the necking region,the microstructure of the material evolved from low-angle grain boundaries(LAGB s) to mixtures of LAGBs and high-angle grain boundaries(HAGBs),and fine equiaxed recrystallized grains.The elongation to failure in the tensile test exceeds 167%.During the hot deformation,continuous dynamic recrystallization of the austenitic matrix was promoted by the multiple secondary phases.The dislocations introduced by the secondary phases were rearranged and continuously transformed into HAGBs.The initially coarse grains(30.5 μm) were refined into ultra-fine equiaxed grains(1 μm),which contributed significantly the enhanced plasticity during hot deformation of the steel.In the necking area of the sample,twins were nucleated in the stress concentration regions and accommodated the local strain by discontinuous dynamic recrystallization,which was also beneficial to improving the plasticity.
基金part of a key project carried out during 2006-2008supported by the National Postdoct Foundation of China (No.20070420417)the Project of the Yunxi Corporation (2007-13A)
文摘Analysis of the Si and AI phases in coal gangue fuel and its ash is important for use of coal gangue ashes. A comprehensive study by theoretical and experimental analyses with differential thermal analysis, X-ray diffraction and Infrared Spectroscopy has been made in the present article to explore the diagram of the Si and Al phases in coal gangue fuel and its ashes. It is found that kaolinite and quartz are the main phases in coal gangue fuel. The ratio of moles A1203 to SiO2 （i.e., Al2O3 （mole） / SiO2 （mole）） is usually no more than 0.5 in most coal gangue fuel and its ashes. The kaolinit at about 984℃ releases a large quantity of SiO2, which makes calcine coal gangue more active than coal gangue itself. The relationship between the ratio A1203 （mole）]SiO2（mole）and the components of coal gangue ash is analyzed, resulting in a formula to calculate the quantity of each phase. Applying the formula to the testing samples from an electric plant in north China supports the above conclusions.
基金financially supported by the International Science and Technology Cooperation Program of China (No.2014DFA53050)
文摘The effect of cerium(Ce)addition on the eutectic Si,β-Al_5Fe Si phase,and the tensile properties of A380 alloy specimens prepared by squeeze-casting were studied by optical microscopy(OM),scanning electron microscopy(SEM),and X-ray diffraction(XRD).The experimental results showed that Ce more effectively modified the eutectic Si and refined theβ-Al_5Fe Si.The refinement effect significantly increased under a specific pressure of 100 MPa with the addition of Ce from 0.1wt%to 0.9wt%.In contrast,the average length and the aspect ratio of the eutectic Si andβ-Al_5Fe Si exhibited their optimal values when the content of the added Ce was greater than 0.5wt%.Needle-like Al_8Cu_4Ce was precipitated with the addition of excessive Ce;hence,the mechanical properties of A380 gradually decreased with increasing Ce content in the range from 0.3wt%to 0.9wt%.
基金financially supported by the National Key Research and Development Program of China (No. 2020YFA0405903)the National Natural Science Foundation of China (Nos. 52001159, 52101141)+1 种基金the Natural Science Foundation of Jiangsu ProvinceChina (No. BK20202010)。
