From a safety point of view, it is important to study the damages and reliability of molten salt reactor structural alloy materials, which are subjected to extreme environments due to neutron irradiation, molten salt ...From a safety point of view, it is important to study the damages and reliability of molten salt reactor structural alloy materials, which are subjected to extreme environments due to neutron irradiation, molten salt corrosion, fission product attacks, thermal stress, and even combinations of these. In the past few years, synchrotron radiation-based materials characterization techniques have proven to be effective in revealing the microstructural evolution and failure mechanisms of the alloys under surrogating operation conditions. Here, we review the recent progress in the investigations of molten salt corrosion,tellurium(Te) corrosion, and alloy design. The valence states and distribution of chromium(Cr) atoms, and the diffusion and local atomic structure of Te atoms near the surface of corroded alloys have been investigated using synchrotron radiation techniques, which considerably deepen the understandings on the molten salt and Te corrosion behaviors. Furthermore, the structure and size distribution of the second phases in the alloys have been obtained, which are helpful for the future development of new alloy materials.展开更多
In this study,pure Ni was demonstrated to protect the GH3535 alloy from Te vapor corrosion because of its strong absorption capacity.Severe Te corrosion of a single GH3535 alloy sample occurred in Te vapor at 700C,whi...In this study,pure Ni was demonstrated to protect the GH3535 alloy from Te vapor corrosion because of its strong absorption capacity.Severe Te corrosion of a single GH3535 alloy sample occurred in Te vapor at 700C,which manifested as complex surface corrosion products and deep intergranular cracks.However,when pure Ni and the GH3535 alloy were put together in the vessel,the GH3535 alloy was completely protected from Te corrosion at the expense of the pure Ni.Thermodynamic calculations proved that the preferential reaction between pure Ni and Te vapor reduced the activity of Te vapor considerably,preventing the corrosion of the GH3535 alloy.Our study reveals one potential approach for protecting the alloys used in molten-salt reactors from Te corrosion.展开更多
An explosion-welded technology was induced to manufacture the GH3535/316H bimetallic plates to provide a more cost-effective structural material for ultrahigh temperature,molten salt thermal storage systems.The micros...An explosion-welded technology was induced to manufacture the GH3535/316H bimetallic plates to provide a more cost-effective structural material for ultrahigh temperature,molten salt thermal storage systems.The microstructure of the bonding interfaces were extensively investigated by scanning electron microscopy,energy dispersive spectrometry,and an electron probe microanalyzer.The bonding interface possessed a periodic,wavy morphology and was adorned by peninsula-or island-like transition zones.At higher magnification,a matrix recrystallization region,fine grain region,columnar grain region,equiaxed grain region,and shrinkage porosity were observed in the transition zones and surrounding area.Electron backscattered diffraction demonstrated that the strain in the recrystallization region of the GH3535 matrix and transition zone was less than the substrate.Strain concentration occurred at the interface and the solidification defects in the transition zone.The dislocation substructure in 316H near the interface was characterized by electron channeling contrast imaging.A dislocation network was formed in the grains of 316H.The microhardness decreased as the distance from the welding interface increased and the lowest hardness was inside the transition zone.展开更多
In this study,the interactions between a Ga-based liquid metal,GaInSn,and several metal materials,including pure metals(Ni and Ti)and alloys(316H stainless steel(SS)and GH3535),at 650℃were investigated.The aim was to...In this study,the interactions between a Ga-based liquid metal,GaInSn,and several metal materials,including pure metals(Ni and Ti)and alloys(316H stainless steel(SS)and GH3535),at 650℃were investigated.The aim was to evaluate the corrosion performance and select a suitable candidate material for use as a molten salt manometer diaphragm in thermal energy storage systems.The results indicated that the alloys(316H SS and GH3535)exhibited less corrosion than pure metals(Ni and Ti)in liquid GaInSn.Ga-rich binary intermetallic compounds were found to form on the surfaces of all the tested metal materials exposed to liquid GaInSn,as a result of the decomposition of liquid GaInSn and its reaction with the constituent elements of the metal materials.The corrosion mechanism for all the tested materials exposed to liquid GaInSn was also investigated and proposed,which may aid in selecting the optimal candidate material when liquid GaInSn is used as the pressure-sensing medium.展开更多
Welding solidification cracking of alloys is associated with the range of solidification temperature that can be greatly affected by the amount of refractory metals and other additives. In this work, solidification cr...Welding solidification cracking of alloys is associated with the range of solidification temperature that can be greatly affected by the amount of refractory metals and other additives. In this work, solidification cracking of Ni-28W-6Cr alloy with high W content was studied by gas tungsten arc welding, showing that the welding current, alloying elements and precipitates all affect the cracking susceptibility. The lengths of cracks increase linearly with the welding current in the range from 150 to 250 A. The relatively high cracking susceptibility is mainly attributed to the high content of Si, which tends to segregate with other elements including W, Cr, Mn as films or components with low melting point in the last solidification stage and weaken the binding force of grain boundaries. Moreover, the existence of precipitated continuous eutectic M_6C carbides in the grain boundaries also acts as nucleation sites of crack initiation, and the cracks often propagate along solidification grain boundary.展开更多
Microstructure and mechanical properties of Ni-28W-6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work.Results showed that original fine-grain base metal near fusion line totall...Microstructure and mechanical properties of Ni-28W-6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work.Results showed that original fine-grain base metal near fusion line totally transformed into coarse heat affected zone after welding.Carbides with different shapes were found in the weld metal and base metal,which all were determined as M6C carbides.In comparison with carbides in base metal,M6C carbides in weld metal are rich in Si and Cr but deficient in W.Moreover,M6C carbides are extremely scarce and hard to be detected in weld metal.Mechanical tests show that the hardness value of weld metal is only about 60%of base metal;the yield strength and tensile strength of welded joint are much lower than those of base metal due to the absence of carbides in weld metal.展开更多
Corrosion test of a Ni–16Mo–7Cr alloy with a decarburized layer was conducted in FLiNaK salt at 700 °C. A detailed microstructure study was performed to investigate the corrosion behavior and mechanisms. The re...Corrosion test of a Ni–16Mo–7Cr alloy with a decarburized layer was conducted in FLiNaK salt at 700 °C. A detailed microstructure study was performed to investigate the corrosion behavior and mechanisms. The results show that the Ferich layers were formed on the corroded alloys with and without decarburization. The surface decarburization had little influence on the corrosion resistance of the alloy, whereas it caused more M_2C carbide formation beneath the corrosion layer. That is attributed to the higher concentration of C gradient near the alloy surface, which was resulted from the increase in C content liberated from graphite crucible wall during the corrosion process.展开更多
基金supported by the National key research and development program of China(Nos.2016YFB0700401 and 2016YFB0700404)Natural Science Foundation of Shanghai(Nos.19ZR1468200 and 18ZR1448000)+2 种基金National Natural Science Foundation of China(Nos.51671154,51601213 and 51671122)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA02004210)Youth Innovation Promotion Association,Chinese Academy of Science(No.2019264)
文摘From a safety point of view, it is important to study the damages and reliability of molten salt reactor structural alloy materials, which are subjected to extreme environments due to neutron irradiation, molten salt corrosion, fission product attacks, thermal stress, and even combinations of these. In the past few years, synchrotron radiation-based materials characterization techniques have proven to be effective in revealing the microstructural evolution and failure mechanisms of the alloys under surrogating operation conditions. Here, we review the recent progress in the investigations of molten salt corrosion,tellurium(Te) corrosion, and alloy design. The valence states and distribution of chromium(Cr) atoms, and the diffusion and local atomic structure of Te atoms near the surface of corroded alloys have been investigated using synchrotron radiation techniques, which considerably deepen the understandings on the molten salt and Te corrosion behaviors. Furthermore, the structure and size distribution of the second phases in the alloys have been obtained, which are helpful for the future development of new alloy materials.
基金the National Natural Science Foundation of China(Nos.U2032205,52171023,51971238,and 52005492)Natural Science Foundation of Shanghai(Nos.20ZR1468600 and 19ZR1468200)+1 种基金Shanghai Sailing Program(No.19YF1458300)the Youth Innovation Promotion Association,Chinese Academy of Science(No.2019264)。
文摘In this study,pure Ni was demonstrated to protect the GH3535 alloy from Te vapor corrosion because of its strong absorption capacity.Severe Te corrosion of a single GH3535 alloy sample occurred in Te vapor at 700C,which manifested as complex surface corrosion products and deep intergranular cracks.However,when pure Ni and the GH3535 alloy were put together in the vessel,the GH3535 alloy was completely protected from Te corrosion at the expense of the pure Ni.Thermodynamic calculations proved that the preferential reaction between pure Ni and Te vapor reduced the activity of Te vapor considerably,preventing the corrosion of the GH3535 alloy.Our study reveals one potential approach for protecting the alloys used in molten-salt reactors from Te corrosion.
基金financially supported by the National Natural Science Foundation of China(Nos.U2032205,51971238,and 52005492)the Shanghai Outstanding Academic Leaders Plan(21XD1404300)+2 种基金the Natural Science Foundation of Shanghai(Nos.18ZR1448000,19ZR 1468200,20ZR1468600,and 21XD1404300)the Shanghai Sailing Program(Grant No.19YF1458300)the Youth Innovation Promotion Association,Chinese Academy of Science(No.2019264).
文摘An explosion-welded technology was induced to manufacture the GH3535/316H bimetallic plates to provide a more cost-effective structural material for ultrahigh temperature,molten salt thermal storage systems.The microstructure of the bonding interfaces were extensively investigated by scanning electron microscopy,energy dispersive spectrometry,and an electron probe microanalyzer.The bonding interface possessed a periodic,wavy morphology and was adorned by peninsula-or island-like transition zones.At higher magnification,a matrix recrystallization region,fine grain region,columnar grain region,equiaxed grain region,and shrinkage porosity were observed in the transition zones and surrounding area.Electron backscattered diffraction demonstrated that the strain in the recrystallization region of the GH3535 matrix and transition zone was less than the substrate.Strain concentration occurred at the interface and the solidification defects in the transition zone.The dislocation substructure in 316H near the interface was characterized by electron channeling contrast imaging.A dislocation network was formed in the grains of 316H.The microhardness decreased as the distance from the welding interface increased and the lowest hardness was inside the transition zone.
基金supported by the National Natural Science Foundation of China(Nos.12005289 and 52071331)the National Key R&D Program of China(No.2019YFA0210000)the State Key Laboratory of Nuclear Detection and Electronics,University of Science and Technology of China(No.SKLPDE-KF-202316)。
文摘In this study,the interactions between a Ga-based liquid metal,GaInSn,and several metal materials,including pure metals(Ni and Ti)and alloys(316H stainless steel(SS)and GH3535),at 650℃were investigated.The aim was to evaluate the corrosion performance and select a suitable candidate material for use as a molten salt manometer diaphragm in thermal energy storage systems.The results indicated that the alloys(316H SS and GH3535)exhibited less corrosion than pure metals(Ni and Ti)in liquid GaInSn.Ga-rich binary intermetallic compounds were found to form on the surfaces of all the tested metal materials exposed to liquid GaInSn,as a result of the decomposition of liquid GaInSn and its reaction with the constituent elements of the metal materials.The corrosion mechanism for all the tested materials exposed to liquid GaInSn was also investigated and proposed,which may aid in selecting the optimal candidate material when liquid GaInSn is used as the pressure-sensing medium.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFB0700404)the National Natural Science Foundation of China(Grant Nos.51601213and 51501216)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA02004210)the Talent development fund of Shanghai(Grant No.201650)
文摘Welding solidification cracking of alloys is associated with the range of solidification temperature that can be greatly affected by the amount of refractory metals and other additives. In this work, solidification cracking of Ni-28W-6Cr alloy with high W content was studied by gas tungsten arc welding, showing that the welding current, alloying elements and precipitates all affect the cracking susceptibility. The lengths of cracks increase linearly with the welding current in the range from 150 to 250 A. The relatively high cracking susceptibility is mainly attributed to the high content of Si, which tends to segregate with other elements including W, Cr, Mn as films or components with low melting point in the last solidification stage and weaken the binding force of grain boundaries. Moreover, the existence of precipitated continuous eutectic M_6C carbides in the grain boundaries also acts as nucleation sites of crack initiation, and the cracks often propagate along solidification grain boundary.
基金funded by the National Natural Science Foundation of China (Grant No.51601213)National Key Research and Development Program of China (Grant No.2016YFB0700404)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA02004210)Talent development fund of Shanghai (Grant No.201650)
文摘Microstructure and mechanical properties of Ni-28W-6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work.Results showed that original fine-grain base metal near fusion line totally transformed into coarse heat affected zone after welding.Carbides with different shapes were found in the weld metal and base metal,which all were determined as M6C carbides.In comparison with carbides in base metal,M6C carbides in weld metal are rich in Si and Cr but deficient in W.Moreover,M6C carbides are extremely scarce and hard to be detected in weld metal.Mechanical tests show that the hardness value of weld metal is only about 60%of base metal;the yield strength and tensile strength of welded joint are much lower than those of base metal due to the absence of carbides in weld metal.
基金supported financially by the National Natural Science Foundation of China (Nos. 51601214, 51674237 and 11705264)the National Key Research and Development Program (No. 2017YFA0402803)
文摘Corrosion test of a Ni–16Mo–7Cr alloy with a decarburized layer was conducted in FLiNaK salt at 700 °C. A detailed microstructure study was performed to investigate the corrosion behavior and mechanisms. The results show that the Ferich layers were formed on the corroded alloys with and without decarburization. The surface decarburization had little influence on the corrosion resistance of the alloy, whereas it caused more M_2C carbide formation beneath the corrosion layer. That is attributed to the higher concentration of C gradient near the alloy surface, which was resulted from the increase in C content liberated from graphite crucible wall during the corrosion process.
