An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560℃ for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temper...An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560℃ for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180℃. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420℃, and then increased;the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180℃ rolling water-quenched alloy were also improved by the presence ofβ″phase. Above 420℃, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.展开更多
Zr-Ti binary alloys are prepared using a nonconsumable tungsten electrode under Ti-gettered inert atmosphere(argon).Microstructures are observed mainly asαphase using x-ray diffraction.A tensile test is performed to ...Zr-Ti binary alloys are prepared using a nonconsumable tungsten electrode under Ti-gettered inert atmosphere(argon).Microstructures are observed mainly asαphase using x-ray diffraction.A tensile test is performed to investigate the tensile strength of a series of Zr-Ti binary alloys at room temperature.The findings indicate that increasing Ti concentration results in an initial increase(<50at%of Ti)and then a decrease in tensile strength.The Zr55Ti45(at%)component exhibits the maximum tensile strength of 1216.68 MPa,which is much higher than that of pure Ti(increased by approximately 200%)or pure Zr(increased by approximately 100%).The potential mechanisms for the remarkable tensile strength are solid solution strengthening and grain refinement.展开更多
Abstract The electrochemical reaction mechanism and electrocrystaUization process of tungsten in the NaCl- KCl-NaF-WO3 molten salt were investigated at 973 K （700℃） by means of cyclic voltammetry, chronopotentiomet...Abstract The electrochemical reaction mechanism and electrocrystaUization process of tungsten in the NaCl- KCl-NaF-WO3 molten salt were investigated at 973 K （700℃） by means of cyclic voltammetry, chronopotentiometry, and chronoamperometry techniques. The results show that the electrochemical reaction process of tungsten in the NaCl-KCl-NaF-WO3 molten salt system is a quasireversible process mix-controlled by ion diffusion rate and electron transport rate. Tungsten ion in this system is reduced to W（0） in two steps. The electrocrystallization process of tungsten is found to be an instantaneous, hemispheroid three-dimensional nucleation process and the tungsten ion diffusion coefficient of 2.361 × 10^-4 cm2.s^-1 is obtained at experimental conditions.展开更多
Thermal expansion is a common phenomenon in both metals and alloys, which is important for metallic material applications in modern industry, especially in nuclear and aerospace industries. A lower thermal expansion c...Thermal expansion is a common phenomenon in both metals and alloys, which is important for metallic material applications in modern industry, especially in nuclear and aerospace industries. A lower thermal expansion coefficient may cause lower thermal stress and higher accuracy. A new Zr-based alloy is developed and presented.The XRD diffraction results demonstrate that only a close-packed hexagonal phase（α or α＇ phase） exists in the microstructure. The thermal expansion and mechanical properties are studied. According to the experimental results, the new Zr-based alloy presents a low thermal expansion coefficient and good mechanical properties.Also,its thermal expansion coefficient is stable through solution treatment.展开更多
The Voronoi structural evolution of silicon upon melting is investigated using a molecular dynamics simulation.At temperatures below the melting point,the solid state system is identified to have a four-fold coordinat...The Voronoi structural evolution of silicon upon melting is investigated using a molecular dynamics simulation.At temperatures below the melting point,the solid state system is identified to have a four-fold coordination structure(4,0,0,0).As the temperature increases,the five−fold coordination(2,3,0,0)and six−fold coordination structures(2,2,2,0)and(0,6,0,0)are observed.This is explained in terms of increasing atomic displacement due to thermal motion and the trapping of the moving atoms by others.At temperatures above the melting point,nearly all of the four-fold coordination structures grows into multiple-fold coordination ones.展开更多
The deformation behavior and microstructure of the Zr50Ti50 alloy in β phase field were investigated by isothermal compression tests at temperatures ranging from 700 to 850 °C and strain rates ranging from 0.001...The deformation behavior and microstructure of the Zr50Ti50 alloy in β phase field were investigated by isothermal compression tests at temperatures ranging from 700 to 850 °C and strain rates ranging from 0.001 to 1 s?1. The flow curves exhibited typical flow softening. The initial discontinuous yielding behavior was observed at higher strain rates, which was not found in other traditional Zr alloys. The apparent deformation activation energy was calculated to be 103 kJ/mol and constitutive equationdescribing the flow stress as a function of the strain rate and deformation temperature was proposed. The analysis indicated that the hot deformation mechanism was mainly dominated by dynamic recovery. However, dynamic recrystallization was delayed by dynamic recovery. Thereafter, the processing map was calculated to evaluate the efficiency of the forging process at the temperatures and strain rates investigated and to optimize processing parameters of hot deformation. The optimum processing parameters were found to be 830?850 °C and 0.56?1 s?1 for hot the deformation of Zr50Ti50 alloy in the β phase region.展开更多
A remarkable enhancement in room-temperature compressive deformability is realized by the minor-addition of 1.5 at.%Al in ZrTi-based bulk metallic glass.Two amorphous phases are observed by transmission electron micro...A remarkable enhancement in room-temperature compressive deformability is realized by the minor-addition of 1.5 at.%Al in ZrTi-based bulk metallic glass.Two amorphous phases are observed by transmission electron microscopy in the Al-containing alloys and this explains the improvement of compression deformability.The studies suggest that phase separation might occur in glass forming alloys with a negative enthalpy of mixing.展开更多
The in situ four-point probe resistivity measurement was used as a main method to study the solid/liquid interfacial characteristics in Ag/Sn/Ag trilayers at temperatures ranging from 150 to 305℃.It is found from the...The in situ four-point probe resistivity measurement was used as a main method to study the solid/liquid interfacial characteristics in Ag/Sn/Ag trilayers at temperatures ranging from 150 to 305℃.It is found from the variation of resistivity that three processes take place on annealing:the dissolution of silver atoms,the diffusion of silver atoms,and the formation of Ag3Sn in liquid tin layer.The first one plays the leading role in the variation of resistivity during annealing process.The apparent diffusivity of silver in liquid tin at 305℃ is determined to be 7.3×10^(-17)cm^(2)/s.展开更多
Single crystals ofβ–FeSi_(2) have been grown from vapor by employing chemical vapor transport technique and using iodine as transport agent in a closed ampoule.In the experiment,β–FeSi_(2) single crystals with wel...Single crystals ofβ–FeSi_(2) have been grown from vapor by employing chemical vapor transport technique and using iodine as transport agent in a closed ampoule.In the experiment,β–FeSi_(2) single crystals with well-developed faces and edges have been observed on the silicon substrate,but no needlelike ones have been found.The changes in the size and the geometric shape of the growth ampoule and temperature gradient are primary factors which result in the variation on β–FeSi_(2) single crystal morphology.展开更多
Undercooled melt of Ge_(73.7)Ni_(26.3) alloy sample floated on B_(2)O_(3 ) melt was subjected to sputtering-deposition of Ni clusters on cooling to induce solidification.The initial temperature of solidification was 9...Undercooled melt of Ge_(73.7)Ni_(26.3) alloy sample floated on B_(2)O_(3 ) melt was subjected to sputtering-deposition of Ni clusters on cooling to induce solidification.The initial temperature of solidification was 975 K.Its undercoolingΔT was 134 K with respect to the melting temperature of the primary phase Ge.On the cooling curve existed dual recalescences representing the transformation of the primary phase(Ge)and the eutectics(Ge+GeNi)respectively.But for the sample unsputtered,only a single exothermic peak presented on the cooling curve with the initial solidification temperature of 904K and undercooling of 205K.Careful observation of the microstructure proved that the Ge phase primarily formed in the sputtering experiment was now formed together with the formation of the eutectics in the experiment without sputtering.展开更多
基金financially supported by the National Basic Research Program of China(No.2013CB733000)the National High Technology Research and Development Program of China(No.2013AA031304)
文摘An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560℃ for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180℃. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420℃, and then increased;the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180℃ rolling water-quenched alloy were also improved by the presence ofβ″phase. Above 420℃, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB731600 and 2013CB733000the National Natural Science Foundation of China under Grant Nos 51121061,51271161 and 51171163.
文摘Zr-Ti binary alloys are prepared using a nonconsumable tungsten electrode under Ti-gettered inert atmosphere(argon).Microstructures are observed mainly asαphase using x-ray diffraction.A tensile test is performed to investigate the tensile strength of a series of Zr-Ti binary alloys at room temperature.The findings indicate that increasing Ti concentration results in an initial increase(<50at%of Ti)and then a decrease in tensile strength.The Zr55Ti45(at%)component exhibits the maximum tensile strength of 1216.68 MPa,which is much higher than that of pure Ti(increased by approximately 200%)or pure Zr(increased by approximately 100%).The potential mechanisms for the remarkable tensile strength are solid solution strengthening and grain refinement.
基金supported by the National Natural Science Foundation of China (No. 51074060)
文摘Abstract The electrochemical reaction mechanism and electrocrystaUization process of tungsten in the NaCl- KCl-NaF-WO3 molten salt were investigated at 973 K （700℃） by means of cyclic voltammetry, chronopotentiometry, and chronoamperometry techniques. The results show that the electrochemical reaction process of tungsten in the NaCl-KCl-NaF-WO3 molten salt system is a quasireversible process mix-controlled by ion diffusion rate and electron transport rate. Tungsten ion in this system is reduced to W（0） in two steps. The electrocrystallization process of tungsten is found to be an instantaneous, hemispheroid three-dimensional nucleation process and the tungsten ion diffusion coefficient of 2.361 × 10^-4 cm2.s^-1 is obtained at experimental conditions.
基金Supported by the Postdoctoral Science Foundation of Hebei Province under Grant No B2017003008the National Natural Science Foundation of China under Grant Nos 51531005,51671166,51571174 and 51604241the Natural Science Foundation of Hebei Province under Grant No E2016203395
文摘Thermal expansion is a common phenomenon in both metals and alloys, which is important for metallic material applications in modern industry, especially in nuclear and aerospace industries. A lower thermal expansion coefficient may cause lower thermal stress and higher accuracy. A new Zr-based alloy is developed and presented.The XRD diffraction results demonstrate that only a close-packed hexagonal phase（α or α＇ phase） exists in the microstructure. The thermal expansion and mechanical properties are studied. According to the experimental results, the new Zr-based alloy presents a low thermal expansion coefficient and good mechanical properties.Also,its thermal expansion coefficient is stable through solution treatment.
基金by the National Natural Science Foundation of China under Grant Nos 50771090,50821001 and 51002130.
文摘The Voronoi structural evolution of silicon upon melting is investigated using a molecular dynamics simulation.At temperatures below the melting point,the solid state system is identified to have a four-fold coordination structure(4,0,0,0).As the temperature increases,the five−fold coordination(2,3,0,0)and six−fold coordination structures(2,2,2,0)and(0,6,0,0)are observed.This is explained in terms of increasing atomic displacement due to thermal motion and the trapping of the moving atoms by others.At temperatures above the melting point,nearly all of the four-fold coordination structures grows into multiple-fold coordination ones.
基金Project(2013CB73300)supported by the National Basic Research Program of ChinaProjects(51531005,51434008,51571174)supported by the National Natural Science Foundation of China
文摘The deformation behavior and microstructure of the Zr50Ti50 alloy in β phase field were investigated by isothermal compression tests at temperatures ranging from 700 to 850 °C and strain rates ranging from 0.001 to 1 s?1. The flow curves exhibited typical flow softening. The initial discontinuous yielding behavior was observed at higher strain rates, which was not found in other traditional Zr alloys. The apparent deformation activation energy was calculated to be 103 kJ/mol and constitutive equationdescribing the flow stress as a function of the strain rate and deformation temperature was proposed. The analysis indicated that the hot deformation mechanism was mainly dominated by dynamic recovery. However, dynamic recrystallization was delayed by dynamic recovery. Thereafter, the processing map was calculated to evaluate the efficiency of the forging process at the temperatures and strain rates investigated and to optimize processing parameters of hot deformation. The optimum processing parameters were found to be 830?850 °C and 0.56?1 s?1 for hot the deformation of Zr50Ti50 alloy in the β phase region.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50731005,50821001 and 50944029the Natural Science Foundation of Hebei Province under Grant No E2010001176.
文摘A remarkable enhancement in room-temperature compressive deformability is realized by the minor-addition of 1.5 at.%Al in ZrTi-based bulk metallic glass.Two amorphous phases are observed by transmission electron microscopy in the Al-containing alloys and this explains the improvement of compression deformability.The studies suggest that phase separation might occur in glass forming alloys with a negative enthalpy of mixing.
文摘The in situ four-point probe resistivity measurement was used as a main method to study the solid/liquid interfacial characteristics in Ag/Sn/Ag trilayers at temperatures ranging from 150 to 305℃.It is found from the variation of resistivity that three processes take place on annealing:the dissolution of silver atoms,the diffusion of silver atoms,and the formation of Ag3Sn in liquid tin layer.The first one plays the leading role in the variation of resistivity during annealing process.The apparent diffusivity of silver in liquid tin at 305℃ is determined to be 7.3×10^(-17)cm^(2)/s.
基金Supported by the National Natural Science Foundation of China under Grant No.59889102.
文摘Single crystals ofβ–FeSi_(2) have been grown from vapor by employing chemical vapor transport technique and using iodine as transport agent in a closed ampoule.In the experiment,β–FeSi_(2) single crystals with well-developed faces and edges have been observed on the silicon substrate,but no needlelike ones have been found.The changes in the size and the geometric shape of the growth ampoule and temperature gradient are primary factors which result in the variation on β–FeSi_(2) single crystal morphology.
文摘Undercooled melt of Ge_(73.7)Ni_(26.3) alloy sample floated on B_(2)O_(3 ) melt was subjected to sputtering-deposition of Ni clusters on cooling to induce solidification.The initial temperature of solidification was 975 K.Its undercoolingΔT was 134 K with respect to the melting temperature of the primary phase Ge.On the cooling curve existed dual recalescences representing the transformation of the primary phase(Ge)and the eutectics(Ge+GeNi)respectively.But for the sample unsputtered,only a single exothermic peak presented on the cooling curve with the initial solidification temperature of 904K and undercooling of 205K.Careful observation of the microstructure proved that the Ge phase primarily formed in the sputtering experiment was now formed together with the formation of the eutectics in the experiment without sputtering.
