Nb-Ti-Si-based ultrahigh-temperature alloys concocted with boron ranging from 0 to 2 at% are prepared by arc-melting technology. The effects of adding boron on their as-melted microstructure and oxidation resistance a...Nb-Ti-Si-based ultrahigh-temperature alloys concocted with boron ranging from 0 to 2 at% are prepared by arc-melting technology. The effects of adding boron on their as-melted microstructure and oxidation resistance are analyzed. The （Nb,Ti）ss, β-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 exist in Nb-22Ti-16Si-6Cr-3Al-4Hf alloy, while （Nb,Ti）ss, α-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 are present in Nb-22Ti-16Si-6Cr-3Al-4Hf-lB and Nb-22Ti-16Si-6Cr-3Al-4Hf-2B alloys. The oxidation of Nb-Ti-Si-based ultrahigh-temperature alloys is dominated by the diffusion of oxygen through （Nb,Ti）ss. Compared to boron-free alloys, the boron-containing alloys have significantly lower oxidation rate when oxidized at 1 200 ℃ for less than 50 h, but, for more than 50 h, their oxidation resistance deteriorates.展开更多
Past fifty years have seen mounting publications on the genesis of volcanic arc magmas.While details remain debated,it is generally agreed that arc magmas result from slab-dehydration induced mantle wedge melting foll...Past fifty years have seen mounting publications on the genesis of volcanic arc magmas.While details remain debated,it is generally agreed that arc magmas result from slab-dehydration induced mantle wedge melting followed by crustal level differentiation of varying extent and sophistication.Two recent arc magma studies deserve particular attention because they attempt to discuss globally unifying controls on arc magma composition.Both Harvard study(Turner and Langmuir,2015a,b)and Rice study(Farner and Lee,2017)show correlations of arc magma composition with crustal thickness and both ascribe the crustal thickness as the principal control on their observed magma compositional variations,yet the physical role of the crustal thickness in their interpretations is markedly different because of(1)the ambiguous use of“crust”and(2)their different magma compositional ranges chosen in discussion.The Harvard study only uses basaltic samples corrected to MgO=6.0 wt.%to discuss mantle processes and interprets the arc crustal thickness as restricting the mantle wedge melting,i.e.,the extent of melting decreases with increasing crustal thickness.The Rice study uses samples of all compositions(basaltic to rhyolitic),whose extent of differentiation increases with increasing crustal thickness,interpreted as Moho-crossing mantle wedge melts travelling greater vertical distance with greater degree of cooling and erupting more evolved compositions above thicker crust than melts erupted above thinner crust without need of invoking mantle wedge processes.We commend these efforts and approve their different approaches but emphasize that the unifying understanding of global arc magmatism requires clearly defined Moho(the base of the crust)and LAB(the lithosphere-asthenosphere boundary)and their intrinsic controls on mantle wedge melting(Harvard Study model)and crustal level magma differentiation(Rice Study model)beneath global arcs.In this study,we use chemical compositions of 36,945 global arc volcanic samples provided by the Rice s展开更多
Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure...Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure and properties of the glass-ceramics was examined. The results show that washing pretreatment of fly ash can decrease alkali metal chloride and increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics. The optimal heat treatment temperature for parent glass of washed fly ash is 1 173 K, at which the crystalline phase of glass-ceramics is composed of gelignite （Ca2A12SiO7） and akermanite （Ca2MgSi207）. Glass-ceramics produced at optimal heat treatment temperature are excellent in term of the physical and chemical properties and leaching characteristics, indicating attractive potential as substitute of nature materials.展开更多
The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding s...The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding speed as a characteristic quantity,the wire melting control ability of twin-body plasma arc was studied by adjusting the current separation ratio(under the condition of a constant total current),the wire current/main current and the position of the wire in the arc axial direction.The results showed that under the premise that the total current remains unchanged(100 A),as the current separation ratio increased,the middle and minimum melting amounts increased approximately synchronously under the effect of anode effect power,the first melting mass range remained constant;the maximum melting amount increased twice as fast as the middle melting amount under the effect of the wire feeding speed,and the second melting mass range was expanded.When the wire current increased,the anode effect power and the plasma arc power were both factors causing the increase in the wire melting amount;however,when the main current increased,the plasma arc power was the only factor causing the increase in the wire melting amount.The average wire melting increment caused by the anode effect power was approximately 2.7 times that caused by the plasma arc power.The minimum melting amount was not affected by the wire-torch distance under any current separation ratio tested.When the current separation ratio increased and reached a threshold,the middle melting amount remained constant with increasing wire-torch distance.When the current separation ratio continued to increase and reached the next threshold,the maximum melting amount remained constant with the increasing wire-torch distance.The effect of the wire-torch distance on the wire melting amount reduced with the increase in the current separation ratio.Through this study,the decoupling mechanism and ability of this innovative arc heat source is more clearly.展开更多
The microstructure and melting properties of ternary Ag-Cu-In intermediate-temperature alloys （400-600 ℃） prepared by electric arc melting were investigated in this work. The melting properties, phase compositions,...The microstructure and melting properties of ternary Ag-Cu-In intermediate-temperature alloys （400-600 ℃） prepared by electric arc melting were investigated in this work. The melting properties, phase compositions, microstructure and hardness were charac- terized by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and micro-hardness tester, respectively. The results show that the melting properties, phase compositions, microstructure and hardness of Ag-Cu-In brazing alloys are substantially different when adding different levels of indium. Indium element could effectively reduce the melting temperatures of （Ag-Cu28）-xIn alloys, and the melting temperatures of （Ag-Cu28）-25In alloy are located at 497.86 and 617.48 ℃. When the indium content varies from 5 wt% and 10 wt%, the dominant phases in the alloys are Ag-rich and Cu-rich phases, and their granular crystals are smaller than 0.5 ktm. When the indium content is higher than 15 wt%, the phase compositions of the alloy are Ag4In and Cu11In9, and the microstructure exhibits dendritic crystals with a uniform distribution. The hardness of （Ag- Cu28）-xIn alloy decreases first and then increases with the content of indium increasing, and the highest hardness of （Ag-Cu28）-25In alloy is HV 266.0.展开更多
Electricity is an efficient form of energy,and the growing interest in electricity-assisted manufacturing is motivated by its inherent energy saving and reduced environmental impact.Beyond this,Electromagnetic Process...Electricity is an efficient form of energy,and the growing interest in electricity-assisted manufacturing is motivated by its inherent energy saving and reduced environmental impact.Beyond this,Electromagnetic Processing of Materials(EPM)allows the fabrication of materials with new compositions,metastable phases and nanograined microstructures that cannot be obtained using conventional heating processes using furnaces.This review covers EPM for the manufacture of ceramic and metal bulk components,with a specific focus on the effects of electric fields and electromagnetic radiations on processing in a wide spectrum of frequencies ranging from DC(f=0 Hz)to visible light(f=10^(14)–10^(15)Hz).The manuscript is divided into two parts.The first part provides a comprehensive overview of the interactions between matter and electric field/current,including heating phenomena(resistive Joule,induction,dielectric heating,electric arcs)and athermal effects(electromigration,electroplasticity,electrochemical reactions,ponderomotive force and others).The second part is focused on the technological application of the techniques,covering heat treatments,joining,sintering and forming.Seven distinct physical phenomena are involved in EPM:resistive Joule and induction heating,electrochemical reactions,electroplasticity,electric arcs and electromagnetic heating based on radio and microwave frequencies(mainly used for heating dielectric materials;i.e.,dielectric heating)or on the IR/visible light(IR heating and lasers).展开更多
基金Foundation item： National Natural Science Foundation of China （50671081）
文摘Nb-Ti-Si-based ultrahigh-temperature alloys concocted with boron ranging from 0 to 2 at% are prepared by arc-melting technology. The effects of adding boron on their as-melted microstructure and oxidation resistance are analyzed. The （Nb,Ti）ss, β-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 exist in Nb-22Ti-16Si-6Cr-3Al-4Hf alloy, while （Nb,Ti）ss, α-（Nb,Ti）5Si3 and γ-（Nb,Ti）5Si3 are present in Nb-22Ti-16Si-6Cr-3Al-4Hf-lB and Nb-22Ti-16Si-6Cr-3Al-4Hf-2B alloys. The oxidation of Nb-Ti-Si-based ultrahigh-temperature alloys is dominated by the diffusion of oxygen through （Nb,Ti）ss. Compared to boron-free alloys, the boron-containing alloys have significantly lower oxidation rate when oxidized at 1 200 ℃ for less than 50 h, but, for more than 50 h, their oxidation resistance deteriorates.
基金started as a research project at Durham University by RABM(2018-2019)under the supervision of YNYN with RABM’s commentssupported by NSFC grant 91958215 and 111 Project(B18048).
文摘Past fifty years have seen mounting publications on the genesis of volcanic arc magmas.While details remain debated,it is generally agreed that arc magmas result from slab-dehydration induced mantle wedge melting followed by crustal level differentiation of varying extent and sophistication.Two recent arc magma studies deserve particular attention because they attempt to discuss globally unifying controls on arc magma composition.Both Harvard study(Turner and Langmuir,2015a,b)and Rice study(Farner and Lee,2017)show correlations of arc magma composition with crustal thickness and both ascribe the crustal thickness as the principal control on their observed magma compositional variations,yet the physical role of the crustal thickness in their interpretations is markedly different because of(1)the ambiguous use of“crust”and(2)their different magma compositional ranges chosen in discussion.The Harvard study only uses basaltic samples corrected to MgO=6.0 wt.%to discuss mantle processes and interprets the arc crustal thickness as restricting the mantle wedge melting,i.e.,the extent of melting decreases with increasing crustal thickness.The Rice study uses samples of all compositions(basaltic to rhyolitic),whose extent of differentiation increases with increasing crustal thickness,interpreted as Moho-crossing mantle wedge melts travelling greater vertical distance with greater degree of cooling and erupting more evolved compositions above thicker crust than melts erupted above thinner crust without need of invoking mantle wedge processes.We commend these efforts and approve their different approaches but emphasize that the unifying understanding of global arc magmatism requires clearly defined Moho(the base of the crust)and LAB(the lithosphere-asthenosphere boundary)and their intrinsic controls on mantle wedge melting(Harvard Study model)and crustal level magma differentiation(Rice Study model)beneath global arcs.In this study,we use chemical compositions of 36,945 global arc volcanic samples provided by the Rice s
基金Funded by the National Natural Science Foundation of China(No.20806051)the Key Laboratory of Education Ministry for Solid Waste Management and Environment Safety(No.SWMES-2010-07)the Science and Technology Project of Housing and Urban-Rural Ministry(No.2010-K4-2)
文摘Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure and properties of the glass-ceramics was examined. The results show that washing pretreatment of fly ash can decrease alkali metal chloride and increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics. The optimal heat treatment temperature for parent glass of washed fly ash is 1 173 K, at which the crystalline phase of glass-ceramics is composed of gelignite （Ca2A12SiO7） and akermanite （Ca2MgSi207）. Glass-ceramics produced at optimal heat treatment temperature are excellent in term of the physical and chemical properties and leaching characteristics, indicating attractive potential as substitute of nature materials.
基金Supported by Youth Program of National Natural Science Foundation of China(Grant No.51905008)Beijing Postdoctoral Research Foundation of China(Grant No.2021-zz-064)+2 种基金Shandong Provincial Major Science and Technology Innovation Project of China(Grant No.2020JMRH0504)Jinan Innovation Team Project of China(Grant No.2021GXRC066)Quancheng Scholars Construction Project of China(Grant No.D03032).
文摘The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding speed as a characteristic quantity,the wire melting control ability of twin-body plasma arc was studied by adjusting the current separation ratio(under the condition of a constant total current),the wire current/main current and the position of the wire in the arc axial direction.The results showed that under the premise that the total current remains unchanged(100 A),as the current separation ratio increased,the middle and minimum melting amounts increased approximately synchronously under the effect of anode effect power,the first melting mass range remained constant;the maximum melting amount increased twice as fast as the middle melting amount under the effect of the wire feeding speed,and the second melting mass range was expanded.When the wire current increased,the anode effect power and the plasma arc power were both factors causing the increase in the wire melting amount;however,when the main current increased,the plasma arc power was the only factor causing the increase in the wire melting amount.The average wire melting increment caused by the anode effect power was approximately 2.7 times that caused by the plasma arc power.The minimum melting amount was not affected by the wire-torch distance under any current separation ratio tested.When the current separation ratio increased and reached a threshold,the middle melting amount remained constant with increasing wire-torch distance.When the current separation ratio continued to increase and reached the next threshold,the maximum melting amount remained constant with the increasing wire-torch distance.The effect of the wire-torch distance on the wire melting amount reduced with the increase in the current separation ratio.Through this study,the decoupling mechanism and ability of this innovative arc heat source is more clearly.
基金financially supported by the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials(No.11zxfk13)the Scientific Research Fund of Sichuan Provincial Education Department(No.14ZB0103)the China Scholarship Council(CSC)
文摘The microstructure and melting properties of ternary Ag-Cu-In intermediate-temperature alloys （400-600 ℃） prepared by electric arc melting were investigated in this work. The melting properties, phase compositions, microstructure and hardness were charac- terized by differential scanning calorimetry （DSC）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and micro-hardness tester, respectively. The results show that the melting properties, phase compositions, microstructure and hardness of Ag-Cu-In brazing alloys are substantially different when adding different levels of indium. Indium element could effectively reduce the melting temperatures of （Ag-Cu28）-xIn alloys, and the melting temperatures of （Ag-Cu28）-25In alloy are located at 497.86 and 617.48 ℃. When the indium content varies from 5 wt% and 10 wt%, the dominant phases in the alloys are Ag-rich and Cu-rich phases, and their granular crystals are smaller than 0.5 ktm. When the indium content is higher than 15 wt%, the phase compositions of the alloy are Ag4In and Cu11In9, and the microstructure exhibits dendritic crystals with a uniform distribution. The hardness of （Ag- Cu28）-xIn alloy decreases first and then increases with the content of indium increasing, and the highest hardness of （Ag-Cu28）-25In alloy is HV 266.0.
基金the Thousand Talents Program of China and Sichuan Province。
文摘Electricity is an efficient form of energy,and the growing interest in electricity-assisted manufacturing is motivated by its inherent energy saving and reduced environmental impact.Beyond this,Electromagnetic Processing of Materials(EPM)allows the fabrication of materials with new compositions,metastable phases and nanograined microstructures that cannot be obtained using conventional heating processes using furnaces.This review covers EPM for the manufacture of ceramic and metal bulk components,with a specific focus on the effects of electric fields and electromagnetic radiations on processing in a wide spectrum of frequencies ranging from DC(f=0 Hz)to visible light(f=10^(14)–10^(15)Hz).The manuscript is divided into two parts.The first part provides a comprehensive overview of the interactions between matter and electric field/current,including heating phenomena(resistive Joule,induction,dielectric heating,electric arcs)and athermal effects(electromigration,electroplasticity,electrochemical reactions,ponderomotive force and others).The second part is focused on the technological application of the techniques,covering heat treatments,joining,sintering and forming.Seven distinct physical phenomena are involved in EPM:resistive Joule and induction heating,electrochemical reactions,electroplasticity,electric arcs and electromagnetic heating based on radio and microwave frequencies(mainly used for heating dielectric materials;i.e.,dielectric heating)or on the IR/visible light(IR heating and lasers).
