The microstructure and phase evolution of Mg-10.16Li-8.14Al-1.46Er alloy of as-cast,250℃+12 h,300℃+12 h,and 400℃+12 h were studied by optical microscopy,scanning electron microscope,and X-ray diffraction.The mechan...The microstructure and phase evolution of Mg-10.16Li-8.14Al-1.46Er alloy of as-cast,250℃+12 h,300℃+12 h,and 400℃+12 h were studied by optical microscopy,scanning electron microscope,and X-ray diffraction.The mechanical properties of Mg-10.16Li-8.14Al-1.46Er alloy in different states were tested by microhardness tester and tension tester.The corrosion resistance of Mg-10.16Li-8.14Al-1.46Er alloy in different states was measured by electrochemical workstation combined with hydrogen evolution and mass loss tests.The results show that the microstructure of as-cast Mg-10.16Li-8.14Al-1.46Er alloy consists ofα,β,AlLi,Al3Er and MgAlLi_(2)phases.Changes of microstructure are morphology and quantity ofαphase,and second phases of MgAlLi_(2)and AlLi by heat treatments at different temperatures.The best comprehensive tensile properties of Mg-10.16Li-8.14Al-1.46Er at 400℃are attributed to theαphase structure,solution strengthening and second phase strengthening.After heat treatments at different temperatures,the corrosion resistance of Mg-10.16Li-8.14Al-1.46Er was improved compared with as-cast samples.The Mg-10.16Li-8.14Al-1.46Er alloy has the best corrosion resistance at 250℃due to the best homogenization at this temperature.展开更多
This paper summarizes the corrosion behavior of Inconel 718 alloy, which is used in the oil and gas fields, including its uniform corrosion, pitting, intergranular corrosion, galvanic corrosion, stress corrosion, and ...This paper summarizes the corrosion behavior of Inconel 718 alloy, which is used in the oil and gas fields, including its uniform corrosion, pitting, intergranular corrosion, galvanic corrosion, stress corrosion, and hydrogen embrittlement. It also analyzes the main reasons for the good corrosion resistance of Inconel 718 alloy. This paper focuses on the effects of the heat-treatment process on corrosive behavior and provides guidelines for reasonable heat treatments in security service environments. Finally, this paper recommends further studies and applications of Inconel 718 in corrosion environments with high-temperature,high-pressure, and wet H2 S.展开更多
Alloying is one of the most effective means to confer superior properties to metal materials.For far too long,conventional W-based alloys were generally improved by the addition of minor elements.The exploitation of c...Alloying is one of the most effective means to confer superior properties to metal materials.For far too long,conventional W-based alloys were generally improved by the addition of minor elements.The exploitation of conventional W-based alloy is restricted to the corner of multielement phase diagrams with tiny compositional space.High-entropy alloys(HEAs)are a novel kind of alloys consisting of multi-principal alloying elements(usually more than 4)and have attracted increasing attention,since they were first reported in 2004.The emergence of HEAs filled the gap of the unexplored central region of multielement phase diagrams.Among them,tungsten-containing HEAs(TCHEAs)exhibit excellent mechanical properties,especially at extraordinarily elevated temperatures.Moreover,recent studies showed that TCHEAs had outstanding irradiation resistance properties.TCHEAs might serve as a promising candidate for plasma-facing materials in the fusion reactor.Many characteristics of TCHEAs are different from other HEAs due to the addition of tungsten with ultrahigh-melting temperature.Here,this paper aimed to introduce the manufacturing routes of TCHEAs;review the phase selection,mechanical properties,and irradiation resistance properties of TCHEAs;and propose the future prospects of TCHEAs.展开更多
In this study, two fluorinated polyurethanes(FPU) containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer(HDI trimer) with fluorin...In this study, two fluorinated polyurethanes(FPU) containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer(HDI trimer) with fluorinated polyesters(CFPETs) having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters(CFPETs) and polyurethanes(CFPUs) were characterized by gel permeation chromatography(GPC), Fourier transform infrared(FTIR) spectroscopy and nuclear magnetic resonance(NMR) measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis(TGA) tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane(CFPU) increased by 190 °C compared with that of the carborane-free fluorinated polyurethane(FPU). Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU(34.3%). The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature(700 °C). It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.展开更多
A resistance random access memory(RRAM) with a structure of Ag/ZnMn2O4/p-Si was fabricated by magnetron sputtering method. Reliable and repeated switching of the resistance of ZnMn2O4 fi lms was obtained between two...A resistance random access memory(RRAM) with a structure of Ag/ZnMn2O4/p-Si was fabricated by magnetron sputtering method. Reliable and repeated switching of the resistance of ZnMn2O4 fi lms was obtained between two well-defi ned states of high and low resistance with a narrow dispersion and 3V switching voltages. Resistance ratio of the high resistance state and low resistance state was found in the range of around 10^3 orders of magnitude and up to about 10^3 test cycles. The retention time of Ag/ZnMn2O4/p-Si device is longer than 10^6 seconds and the resistance ratio between two states remains higher than 10^3 at room temperature, showing a remarkable reliability performance of the RRAM devices for nonvolatile memory application. The equivalent simulation circuits for HRS(high resistance state) and LRS(low resistance state) were also studied by impedance spectroscopy.展开更多
The influence of chemical composition on corrosion resistance of AZ91D magnesium alloys ingots has been investigated. Mass loss method was applied to evaluate the corrosion resistance of AZ91D alloys and the data were...The influence of chemical composition on corrosion resistance of AZ91D magnesium alloys ingots has been investigated. Mass loss method was applied to evaluate the corrosion resistance of AZ91D alloys and the data were analyzed by multiple regression. The results show that the corrosion resistance of this alloy can be improved by increasing Al, Zn and Mn in a certain degree, and will drop with increasing Si and heavy metals (Fe, Cu, Ni). It is found that ingots received from company F should be listed into unusable materials in terms of the corrosion resistance, while among the five suppliers, the only local company E supplied excellent AZ91D magnesium alloy ingots with the best corrosion resistance.展开更多
The existing form and reaction mechanism of Sb in heat resistane Mg-Gd-Y-Sb rare earth magnesium alloy were investigated by inductive coupled plasma emission spectroscopy(ICP),scanning electron microscopy(SEM),energy ...The existing form and reaction mechanism of Sb in heat resistane Mg-Gd-Y-Sb rare earth magnesium alloy were investigated by inductive coupled plasma emission spectroscopy(ICP),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and X-ray diffraction(XRD).It is found that Sb tends to form high melting point intermetallics with rare earth elements of Gd and Y.The existing form of Sb is determined to be GdSb and SbY,respectively,which has high melting point(GdSb:2142℃/SbY:1782℃).Meanwhile,the first principle calculation and electronegativity difference calculation were performed to further understand the reaction mechanism.Therefore,the forming heat and binding energy were calculated.The experimental results show that the binding tendency of Sb element to Gd and Y is much stronger than that of it with other elements in this alloy,which results in the formation of high melting point of Gd-Sb and Y-Sb intermetallics,and finally leads to the high temperature resistant further improvement of the Mg-Gd-Y magnesium alloy.展开更多
A two-step equal channel angular extrusion(ECAE) procedure was used to process pure Mg. The effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg were...A two-step equal channel angular extrusion(ECAE) procedure was used to process pure Mg. The effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg were studied. The results show that the average grain size of pure Mg decreases with decreasing extrusion temperature. After ECAE processing at 473 K, fine and equiaxed grains(~9 μm) are obtained. The sample processed at 473 K exhibits the excellent mechanical properties, whereas the sample processed at 633 K has the lowest corrosion rate. The improved corrosion resistance and mechanical properties of pure Mg by ECAE are ascribed to grain refinement and microstructural modification.展开更多
A new kind of corrosion resistant steelfor cargo oiltanks(COT)was developed.The influences of finalrolling temperature,cooling rate,and finalcooling temperature on microstructure were investigated.The proper rolling...A new kind of corrosion resistant steelfor cargo oiltanks(COT)was developed.The influences of finalrolling temperature,cooling rate,and finalcooling temperature on microstructure were investigated.The proper rolling process parameters were obtained through multi-pass thermalsimulation test.The finalrolling temperature is about 820 ℃,the finalcooling temperature is about 600 ℃,and the cooling rate should be controlled between 10 ℃/s and 20 ℃/s.Based on the above analysis of the results,three groups of rolling samples by thermo mechanicalcontrolprocess are prepared.The tensile strength,yield strength,and toughness of the corrosion resistant steelare measured,which meet the requirements of DH36 steel,it can instruct the actualrolling production.The corrosion behaviour is also researched by weight loss and electrochemicalimpedance spectroscopic method,and it is found that the steelhas good corrosion resistance performance,the best one is No.3 steel,the corrosion rate of which is about 1/4 of the accepted criterion.展开更多
The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercr...The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe(Cr,Mo)23C6,V(Nb)C,and(Fe2Mo) Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe(Cr,Mo)23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What's more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.展开更多
Crystal morphologies and resistivity of polysilicon trap-rich layers of two-generation trap-rich silicon-on-insulator(TR-SOI) substrates are studied. It is found that the resistivity of the trap-rich layer of genera...Crystal morphologies and resistivity of polysilicon trap-rich layers of two-generation trap-rich silicon-on-insulator(TR-SOI) substrates are studied. It is found that the resistivity of the trap-rich layer of generation 2(TR-G2)is higher than that of generation 1(TR-G1), although the crystal morphologies of the trap rich layers are the same. In addition, the rf performance of two-generation TR-SOI substrates is investigated by coplanar waveguide lines and inductors. The results show that both the rf loss and the second harmonic distortion of TR-G2 are smaller than those of TR-G1. These results can be attributed to the higher resistivity values of both the trap-rich layer and the high-resistivity silicon(HR-Si) substrate of TR-G2. Moreover, the rf performance of the TR-SOI substrate with thicker buried oxide is slightly better. The second harmonics of various TR-SOI substrates are simulated and evaluated with the harmonic quality factor model as well. It can be predicted that the TR-SOI substrate will see further improvement in rf performance if the resistivities of both the trap-rich layer and HR-Si substrate increase.展开更多
The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite (w(MgO)=95%) as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the...The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite (w(MgO)=95%) as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550℃ for 3h using Baosteel tundish slag and static crucible method. The result indicates that: introducing Si3N4 could obviously improve the slag resistance of MgO based castable, which increased with increasing Si3N4. Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable, the partial-pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere, Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.展开更多
The relationship of corrosion resistance and antifouling behavior of 19 Cu alloys exposed to seawater of Qingdao ,Xiamen,Yulin sea areas in China for 1,2,4,8 year intervals was studied .The experiments were carried on...The relationship of corrosion resistance and antifouling behavior of 19 Cu alloys exposed to seawater of Qingdao ,Xiamen,Yulin sea areas in China for 1,2,4,8 year intervals was studied .The experiments were carried on by analyzing the composition of corrosion films formed on the surface of alloy specimens during the immersion time and by using OM,SEM,EDXA and AES experiment methods.The results verify the view point that it is the cuprous oxide film which played an important role in antifouling property of Cu alloys in seawater and throw a light on the view point in details further.The influence of different sea areas on the antifouling property of Cu alloys is also discussed.展开更多
In this paper, Ni-based alloy composite coating reinforced by Ti (C, N) particles was fabricated on the mild steel through laser cladding technology. The microstrncture of laser cladding layer was analyzed by means ...In this paper, Ni-based alloy composite coating reinforced by Ti (C, N) particles was fabricated on the mild steel through laser cladding technology. The microstrncture of laser cladding layer was analyzed by means of optical microscopy (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The wear resistance test of the coating was evaluated using an M-2000 tester. The results showed that the Ni-based composite coating had an ability of rapid solidification to form dendritic crystals microstructure consisting of Ti ( C, N) particulates uniformly distributed in the matrix. It was found that some Ti( C,N) particles are similar to be round in shape, and the others are irregular. Laser cladding layer reinforced by Ti( C, N) particulates was found to possess good wear resistance property.展开更多
A new type of transparent scratch resistant coatings including in-situ modified SiO2 (g-SiO2) in flame spray pyrolysis (FSP) process was prepared. The maximum content of g-SiO2 in the coating was 15 wt%, which is ...A new type of transparent scratch resistant coatings including in-situ modified SiO2 (g-SiO2) in flame spray pyrolysis (FSP) process was prepared. The maximum content of g-SiO2 in the coating was 15 wt%, which is higher than that of SiO2 modified by traditional wet chemical route (I-SiO2, only 10 wt%). The results of transmission electron microscopy have demonstrated that in-situ surface modified g-SiO2 particles dispersed well with smaller agglomerates in the final coating, which was much better than the particles modified via wet chemical route. Visible light transmittance and haze tests were introduced to characterize the optical quality of the films. All coatings were highly transparent with the visible light transmittance of above 80%, especially for coatings containing g-SiO2, which exhibited slightly higher visible light transmittance than l-SiO2 embedded one. The haze value of coatings incorporated with 15 wt% g-SiO2 was 1.85%, even lower than the coating with 5 wt% I-SiO2 (haze value of 2.09%), indicating much better clarity of g-SiO2. The excellent optical property of g-SiO2 filled coatings was attributed to the good dispersion and distribution of particles. Nano-indention and nano-scratch tests were con- ducted to investigate the scratch resistance of coatings on nano-scale. The surface hardness of the coatings rose by 18% and 14%, and the average friction coefficient decreased by 15% and 11%, respectively, compared to the neat coat due to the addition of 10 wt% g-SiO2 and I-SiO2. The pencil hardness of the coating with 15 wt% g-SiO2 increased from 2B for the neat coating to 2H. However, the pencil hardness of coating with 10 wt% I-SiO2 was only H. The results showed that the g-SiO2 embedded coatings exhibited higher scratch resistance and better optical properties.展开更多
Ultrasonic vibration with different powers from 0 k W to 1.6 k W was applied during the tungsten inert gas welding-brazing of Mg/Ti.The microstructures,mechanical properties and corrosion resistance of the ultrasonic ...Ultrasonic vibration with different powers from 0 k W to 1.6 k W was applied during the tungsten inert gas welding-brazing of Mg/Ti.The microstructures,mechanical properties and corrosion resistance of the ultrasonic assisted tungsten inert gas(U-TIG) welded-brazed Mg/Ti joint were characterized.The results showed that,without being subjected to ultrasonic vibration,coarse columnar α-Mg grains occurred in the fusion zone of Mg/Ti joint.However,with ultrasonic power of 1.2 k W,the average grain size of columnar α-Mg grains was refined from 200 μm to about 50 μm and the tensile strength of joints increased^18% up to 228 MPa.Besides,high fraction of grain boundaries was introduced by grain refinement,contributing to improve the corrosion resistance in two ways:(i) accelerating the formation of Mg(OH)2protective layer and(ii) reducing the mismatch and disorder between Mg(OH)2 protective layer and Mg alloy surface.展开更多
The influences of rare earth elements(cerium and lanthanum) on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy(SEM), ...The influences of rare earth elements(cerium and lanthanum) on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD) and differential scanning calorimetry(DSC). The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.展开更多
The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^+-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties ...The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^+-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties were investigated.A distinct bipolar resistive switching behavior of the devices was observed at room temperature.The resistance ratio R_(HRS)/RLRS of high resistance state and low resistance state is as large as four orders of magnitude with a readout voltage of 2.0 V.The dominant conduction mechanism of the device is trap-controlled space charge limited current(SCLC).The devices exhibit good durability under 1×10^3cycles and the degradation is invisible for more than 10^6 s.展开更多
Sheet samples of Mg-8Li,Mg-8Li-3Al,Mg-8Li-3AlSi and Mg-8Li-5AlSi alloys were obtained by hot rolling.Optical microscope,microhardness tester,nanoindentor,X-ray diffractometer and electrochemical analyzer were adopted ...Sheet samples of Mg-8Li,Mg-8Li-3Al,Mg-8Li-3AlSi and Mg-8Li-5AlSi alloys were obtained by hot rolling.Optical microscope,microhardness tester,nanoindentor,X-ray diffractometer and electrochemical analyzer were adopted to investigate the microstructures,micro-mechanical properties and corrosion resistance.Roller was preheated to 150°C before rolling process,and rolling reduction designed was about20% per pass with a total rolling reduction of 84%.The rolled plates were annealed at 200°C for 120 min.The tensile tests were performed at room temperature.Experimental results showed that both the strength and corrosion resistance of theα+βdual-phase of Mg-Li alloy were significantly improved with adding Al-Si elements.The strength enhancement was attributed to the solid solution of Al into theα-Mg matrix and into theβ-Li matrix as well as to the precipitation strengthening of Mg2 Si particles.Besides,the dendrite grains ofα-Mg transformed to equiaxed ones with addition of Al into alloy Mg-Li.展开更多
Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy(OM),scannin...Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy(OM),scanning electronic microscopy(SEM), X-ray diffraction(XRD), mechanical properties testing, and electrochemical measurement. The as-cast Mg–9Li–3Al–1.6Y alloy with the average grain size of 325 lm is composed of b-Li matrix, block a-Mg, and granule Al2Y phases. After extrusion, the grain size of the as-cast alloy is obviously refined and reaches to 75 lm; the strength and elongation of the extruded alloy are enhanced by 17.20 % and49.45 %, respectively, owing to their fine microstructure and reduction of casting defects. The as-extruded alloy shows better corrosion resistance compared to the as-cast one, which may be related to the low stored energy and dislocation density in the extruded alloy, also the homogenization treatment before extrusion.展开更多
基金funded by the National Natural Science Foundation of China(No.51801185)Key Research Project of the Higher Education Institutions of Henan Province,Henan Provincial Department of Education,China(No.19A460007)TrainingProgram for Young Backbone Teachers of the Higher Education Institutions of Henan Province,China.
文摘The microstructure and phase evolution of Mg-10.16Li-8.14Al-1.46Er alloy of as-cast,250℃+12 h,300℃+12 h,and 400℃+12 h were studied by optical microscopy,scanning electron microscope,and X-ray diffraction.The mechanical properties of Mg-10.16Li-8.14Al-1.46Er alloy in different states were tested by microhardness tester and tension tester.The corrosion resistance of Mg-10.16Li-8.14Al-1.46Er alloy in different states was measured by electrochemical workstation combined with hydrogen evolution and mass loss tests.The results show that the microstructure of as-cast Mg-10.16Li-8.14Al-1.46Er alloy consists ofα,β,AlLi,Al3Er and MgAlLi_(2)phases.Changes of microstructure are morphology and quantity ofαphase,and second phases of MgAlLi_(2)and AlLi by heat treatments at different temperatures.The best comprehensive tensile properties of Mg-10.16Li-8.14Al-1.46Er at 400℃are attributed to theαphase structure,solution strengthening and second phase strengthening.After heat treatments at different temperatures,the corrosion resistance of Mg-10.16Li-8.14Al-1.46Er was improved compared with as-cast samples.The Mg-10.16Li-8.14Al-1.46Er alloy has the best corrosion resistance at 250℃due to the best homogenization at this temperature.
文摘This paper summarizes the corrosion behavior of Inconel 718 alloy, which is used in the oil and gas fields, including its uniform corrosion, pitting, intergranular corrosion, galvanic corrosion, stress corrosion, and hydrogen embrittlement. It also analyzes the main reasons for the good corrosion resistance of Inconel 718 alloy. This paper focuses on the effects of the heat-treatment process on corrosive behavior and provides guidelines for reasonable heat treatments in security service environments. Finally, this paper recommends further studies and applications of Inconel 718 in corrosion environments with high-temperature,high-pressure, and wet H2 S.
基金financially supported by National MCF Energy Research and Development Program(Grant No.2018YFE0312400)National Natural Science Foundation of China(Grant Nos.51822402 and 51671044)+3 种基金National Key Research and Development Program of China(Grant Nos.2019YFA0209901 and 2018YFA0702901)Liao Ning Revitalization Talents Program(Grant No.XLYC1807047)Fund of Science and Technology on Reactor Fuel and Materials Laboratory(Grant No.6142A06190304)Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University(Grant No.SKLSP201902)
文摘Alloying is one of the most effective means to confer superior properties to metal materials.For far too long,conventional W-based alloys were generally improved by the addition of minor elements.The exploitation of conventional W-based alloy is restricted to the corner of multielement phase diagrams with tiny compositional space.High-entropy alloys(HEAs)are a novel kind of alloys consisting of multi-principal alloying elements(usually more than 4)and have attracted increasing attention,since they were first reported in 2004.The emergence of HEAs filled the gap of the unexplored central region of multielement phase diagrams.Among them,tungsten-containing HEAs(TCHEAs)exhibit excellent mechanical properties,especially at extraordinarily elevated temperatures.Moreover,recent studies showed that TCHEAs had outstanding irradiation resistance properties.TCHEAs might serve as a promising candidate for plasma-facing materials in the fusion reactor.Many characteristics of TCHEAs are different from other HEAs due to the addition of tungsten with ultrahigh-melting temperature.Here,this paper aimed to introduce the manufacturing routes of TCHEAs;review the phase selection,mechanical properties,and irradiation resistance properties of TCHEAs;and propose the future prospects of TCHEAs.
基金financially supported by International Cooperative Project (Harbin Institute of Technology 2014DFR40370)International Cooperative Project (Wuxi HIT Limited Corporation & Research Institute of New Materials BZ2015024)
文摘In this study, two fluorinated polyurethanes(FPU) containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer(HDI trimer) with fluorinated polyesters(CFPETs) having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters(CFPETs) and polyurethanes(CFPUs) were characterized by gel permeation chromatography(GPC), Fourier transform infrared(FTIR) spectroscopy and nuclear magnetic resonance(NMR) measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis(TGA) tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane(CFPU) increased by 190 °C compared with that of the carborane-free fluorinated polyurethane(FPU). Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU(34.3%). The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature(700 °C). It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.
基金Funded by the National Natural Science Foundation of China(51262003)the Guangxi Key Laboratory of Information Materials(Guilin University of Electronic Technology),China(No.1110908-10-Z)
文摘A resistance random access memory(RRAM) with a structure of Ag/ZnMn2O4/p-Si was fabricated by magnetron sputtering method. Reliable and repeated switching of the resistance of ZnMn2O4 fi lms was obtained between two well-defi ned states of high and low resistance with a narrow dispersion and 3V switching voltages. Resistance ratio of the high resistance state and low resistance state was found in the range of around 10^3 orders of magnitude and up to about 10^3 test cycles. The retention time of Ag/ZnMn2O4/p-Si device is longer than 10^6 seconds and the resistance ratio between two states remains higher than 10^3 at room temperature, showing a remarkable reliability performance of the RRAM devices for nonvolatile memory application. The equivalent simulation circuits for HRS(high resistance state) and LRS(low resistance state) were also studied by impedance spectroscopy.
文摘The influence of chemical composition on corrosion resistance of AZ91D magnesium alloys ingots has been investigated. Mass loss method was applied to evaluate the corrosion resistance of AZ91D alloys and the data were analyzed by multiple regression. The results show that the corrosion resistance of this alloy can be improved by increasing Al, Zn and Mn in a certain degree, and will drop with increasing Si and heavy metals (Fe, Cu, Ni). It is found that ingots received from company F should be listed into unusable materials in terms of the corrosion resistance, while among the five suppliers, the only local company E supplied excellent AZ91D magnesium alloy ingots with the best corrosion resistance.
基金Funded by the National Natural Science Foundation of China(No.U1837207)。
文摘The existing form and reaction mechanism of Sb in heat resistane Mg-Gd-Y-Sb rare earth magnesium alloy were investigated by inductive coupled plasma emission spectroscopy(ICP),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and X-ray diffraction(XRD).It is found that Sb tends to form high melting point intermetallics with rare earth elements of Gd and Y.The existing form of Sb is determined to be GdSb and SbY,respectively,which has high melting point(GdSb:2142℃/SbY:1782℃).Meanwhile,the first principle calculation and electronegativity difference calculation were performed to further understand the reaction mechanism.Therefore,the forming heat and binding energy were calculated.The experimental results show that the binding tendency of Sb element to Gd and Y is much stronger than that of it with other elements in this alloy,which results in the formation of high melting point of Gd-Sb and Y-Sb intermetallics,and finally leads to the high temperature resistant further improvement of the Mg-Gd-Y magnesium alloy.
基金financially supported by the National Natural Science Foundation of China (Nos. 81330031 and 81271701)
文摘A two-step equal channel angular extrusion(ECAE) procedure was used to process pure Mg. The effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg were studied. The results show that the average grain size of pure Mg decreases with decreasing extrusion temperature. After ECAE processing at 473 K, fine and equiaxed grains(~9 μm) are obtained. The sample processed at 473 K exhibits the excellent mechanical properties, whereas the sample processed at 633 K has the lowest corrosion rate. The improved corrosion resistance and mechanical properties of pure Mg by ECAE are ascribed to grain refinement and microstructural modification.
基金Funded by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China during the“12th Five-Year Plan”(No.2011BAE25B03)
文摘A new kind of corrosion resistant steelfor cargo oiltanks(COT)was developed.The influences of finalrolling temperature,cooling rate,and finalcooling temperature on microstructure were investigated.The proper rolling process parameters were obtained through multi-pass thermalsimulation test.The finalrolling temperature is about 820 ℃,the finalcooling temperature is about 600 ℃,and the cooling rate should be controlled between 10 ℃/s and 20 ℃/s.Based on the above analysis of the results,three groups of rolling samples by thermo mechanicalcontrolprocess are prepared.The tensile strength,yield strength,and toughness of the corrosion resistant steelare measured,which meet the requirements of DH36 steel,it can instruct the actualrolling production.The corrosion behaviour is also researched by weight loss and electrochemicalimpedance spectroscopic method,and it is found that the steelhas good corrosion resistance performance,the best one is No.3 steel,the corrosion rate of which is about 1/4 of the accepted criterion.
基金supported by the Science and Technology Program of Sichuan Province,China(No.2013GZX0146)
文摘The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe(Cr,Mo)23C6,V(Nb)C,and(Fe2Mo) Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe(Cr,Mo)23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What's more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61376021 and 61674159the Program of Shanghai Academic/Technology Research Leader under Grant No 17XD1424500
文摘Crystal morphologies and resistivity of polysilicon trap-rich layers of two-generation trap-rich silicon-on-insulator(TR-SOI) substrates are studied. It is found that the resistivity of the trap-rich layer of generation 2(TR-G2)is higher than that of generation 1(TR-G1), although the crystal morphologies of the trap rich layers are the same. In addition, the rf performance of two-generation TR-SOI substrates is investigated by coplanar waveguide lines and inductors. The results show that both the rf loss and the second harmonic distortion of TR-G2 are smaller than those of TR-G1. These results can be attributed to the higher resistivity values of both the trap-rich layer and the high-resistivity silicon(HR-Si) substrate of TR-G2. Moreover, the rf performance of the TR-SOI substrate with thicker buried oxide is slightly better. The second harmonics of various TR-SOI substrates are simulated and evaluated with the harmonic quality factor model as well. It can be predicted that the TR-SOI substrate will see further improvement in rf performance if the resistivities of both the trap-rich layer and HR-Si substrate increase.
文摘The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite (w(MgO)=95%) as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550℃ for 3h using Baosteel tundish slag and static crucible method. The result indicates that: introducing Si3N4 could obviously improve the slag resistance of MgO based castable, which increased with increasing Si3N4. Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable, the partial-pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere, Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.
文摘The relationship of corrosion resistance and antifouling behavior of 19 Cu alloys exposed to seawater of Qingdao ,Xiamen,Yulin sea areas in China for 1,2,4,8 year intervals was studied .The experiments were carried on by analyzing the composition of corrosion films formed on the surface of alloy specimens during the immersion time and by using OM,SEM,EDXA and AES experiment methods.The results verify the view point that it is the cuprous oxide film which played an important role in antifouling property of Cu alloys in seawater and throw a light on the view point in details further.The influence of different sea areas on the antifouling property of Cu alloys is also discussed.
文摘In this paper, Ni-based alloy composite coating reinforced by Ti (C, N) particles was fabricated on the mild steel through laser cladding technology. The microstrncture of laser cladding layer was analyzed by means of optical microscopy (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The wear resistance test of the coating was evaluated using an M-2000 tester. The results showed that the Ni-based composite coating had an ability of rapid solidification to form dendritic crystals microstructure consisting of Ti ( C, N) particulates uniformly distributed in the matrix. It was found that some Ti( C,N) particles are similar to be round in shape, and the others are irregular. Laser cladding layer reinforced by Ti( C, N) particulates was found to possess good wear resistance property.
基金supported by the National Natural Science Foundation of China (Nos. 51173043, 21236003, and 21322607)the Basic Research Program of Shanghai (Nos. 13JC1408100 and 15JC1401300)+1 种基金the Key Scientific and Technological Program of Shanghai (No. 14521100800)the Fundamental Research Funds for the Central Universities.
文摘A new type of transparent scratch resistant coatings including in-situ modified SiO2 (g-SiO2) in flame spray pyrolysis (FSP) process was prepared. The maximum content of g-SiO2 in the coating was 15 wt%, which is higher than that of SiO2 modified by traditional wet chemical route (I-SiO2, only 10 wt%). The results of transmission electron microscopy have demonstrated that in-situ surface modified g-SiO2 particles dispersed well with smaller agglomerates in the final coating, which was much better than the particles modified via wet chemical route. Visible light transmittance and haze tests were introduced to characterize the optical quality of the films. All coatings were highly transparent with the visible light transmittance of above 80%, especially for coatings containing g-SiO2, which exhibited slightly higher visible light transmittance than l-SiO2 embedded one. The haze value of coatings incorporated with 15 wt% g-SiO2 was 1.85%, even lower than the coating with 5 wt% I-SiO2 (haze value of 2.09%), indicating much better clarity of g-SiO2. The excellent optical property of g-SiO2 filled coatings was attributed to the good dispersion and distribution of particles. Nano-indention and nano-scratch tests were con- ducted to investigate the scratch resistance of coatings on nano-scale. The surface hardness of the coatings rose by 18% and 14%, and the average friction coefficient decreased by 15% and 11%, respectively, compared to the neat coat due to the addition of 10 wt% g-SiO2 and I-SiO2. The pencil hardness of the coating with 15 wt% g-SiO2 increased from 2B for the neat coating to 2H. However, the pencil hardness of coating with 10 wt% I-SiO2 was only H. The results showed that the g-SiO2 embedded coatings exhibited higher scratch resistance and better optical properties.
基金financially supported by the National Natural Science Foundation of China(No.51205428)the Fundamental Research Funds for the Central Universities(Nos.CDJZR13130040and CDJZR12130047)
文摘Ultrasonic vibration with different powers from 0 k W to 1.6 k W was applied during the tungsten inert gas welding-brazing of Mg/Ti.The microstructures,mechanical properties and corrosion resistance of the ultrasonic assisted tungsten inert gas(U-TIG) welded-brazed Mg/Ti joint were characterized.The results showed that,without being subjected to ultrasonic vibration,coarse columnar α-Mg grains occurred in the fusion zone of Mg/Ti joint.However,with ultrasonic power of 1.2 k W,the average grain size of columnar α-Mg grains was refined from 200 μm to about 50 μm and the tensile strength of joints increased^18% up to 228 MPa.Besides,high fraction of grain boundaries was introduced by grain refinement,contributing to improve the corrosion resistance in two ways:(i) accelerating the formation of Mg(OH)2protective layer and(ii) reducing the mismatch and disorder between Mg(OH)2 protective layer and Mg alloy surface.
基金Funded by the National Natural Science Foundation of China(No.51379070)the Fundamental Research Funds for the Central Universities(No.2017B40314)
文摘The influences of rare earth elements(cerium and lanthanum) on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD) and differential scanning calorimetry(DSC). The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.
基金Funded by the National Natural Science Foundation of China(No.51262003)the Guangxi Key Laboratory of Information Materials(Guilin University of Electronic Technology),China(No.1110908-10-Z)
文摘The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^+-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties were investigated.A distinct bipolar resistive switching behavior of the devices was observed at room temperature.The resistance ratio R_(HRS)/RLRS of high resistance state and low resistance state is as large as four orders of magnitude with a readout voltage of 2.0 V.The dominant conduction mechanism of the device is trap-controlled space charge limited current(SCLC).The devices exhibit good durability under 1×10^3cycles and the degradation is invisible for more than 10^6 s.
基金supported by National Natural Science Foundation of China(51274149,51401143)Shanxi Scholarship Council of China(No.2014-029)
文摘Sheet samples of Mg-8Li,Mg-8Li-3Al,Mg-8Li-3AlSi and Mg-8Li-5AlSi alloys were obtained by hot rolling.Optical microscope,microhardness tester,nanoindentor,X-ray diffractometer and electrochemical analyzer were adopted to investigate the microstructures,micro-mechanical properties and corrosion resistance.Roller was preheated to 150°C before rolling process,and rolling reduction designed was about20% per pass with a total rolling reduction of 84%.The rolled plates were annealed at 200°C for 120 min.The tensile tests were performed at room temperature.Experimental results showed that both the strength and corrosion resistance of theα+βdual-phase of Mg-Li alloy were significantly improved with adding Al-Si elements.The strength enhancement was attributed to the solid solution of Al into theα-Mg matrix and into theβ-Li matrix as well as to the precipitation strengthening of Mg2 Si particles.Besides,the dendrite grains ofα-Mg transformed to equiaxed ones with addition of Al into alloy Mg-Li.
基金financially supported by the National Basic Research Program of China (No. 2007CB613702)the International Scientific and Technological Cooperation Projects (No. 2010DFR50010)
文摘Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy(OM),scanning electronic microscopy(SEM), X-ray diffraction(XRD), mechanical properties testing, and electrochemical measurement. The as-cast Mg–9Li–3Al–1.6Y alloy with the average grain size of 325 lm is composed of b-Li matrix, block a-Mg, and granule Al2Y phases. After extrusion, the grain size of the as-cast alloy is obviously refined and reaches to 75 lm; the strength and elongation of the extruded alloy are enhanced by 17.20 % and49.45 %, respectively, owing to their fine microstructure and reduction of casting defects. The as-extruded alloy shows better corrosion resistance compared to the as-cast one, which may be related to the low stored energy and dislocation density in the extruded alloy, also the homogenization treatment before extrusion.