The formation of precipitates and their effect on mechanical properties and irradiation damage in V-4CraTi alloys have been investigated using transmission electron microscope,high-temperature tensile tests and high-v...The formation of precipitates and their effect on mechanical properties and irradiation damage in V-4CraTi alloys have been investigated using transmission electron microscope,high-temperature tensile tests and high-voltage electron microscope (HVEM).V-4Cr-4Ti alloys were aged for 20-40 h at 873 K,and extremely fine precipitates were produced during the aging process,which coarsened with aging time.The results of high-temperature (773,873 and 973 K)tensile tests showed an increase in strength with increasing aging time (i.e:,increasing size of precipitates)while a decrease in the uniform elongation.There was evidence that presence of precipitates strengthened V-4Cr-4Ti alloys.In situ HVEM observations showed that the precipitates restricted the growth rate of dislocation loops induced during electron irradiation at 773 K.The interactions between precipitates and irradiation-induced dislocation loops were discussed.The presence of particles alleviated the increase in irradiation hardening up to an irradiation dose of 3.42 dpa (displacement per atom).The precipitates shrank in size during electron irradiation,which was due to the dissolution of constituent atoms of the precipitates into the alloy matrix.展开更多
The different influences of the general grain boundary and the twin boundary on the cavity formation were investigated in copper irradiated by helium at room temperature. Large number of the cavities with sizes smalle...The different influences of the general grain boundary and the twin boundary on the cavity formation were investigated in copper irradiated by helium at room temperature. Large number of the cavities with sizes smaller than 5 nm formed after irradiation, which were almost homogenously distributed inside the grains. However, the distribution of the cavities varied near the general grain boundary and the twin boundary. Cavities-depleted zone was readily observed near the general grain boundaries, which was rarely observed near the twin boundaries. Meanwhile, decoration of dense cavities within the grain boundary plane was observed. The results suggested the limited influence of the twin boundaries as the point defect sinks compared with the general grain boundaries.展开更多
Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures.The annealing process made the defects develop into large dislocation loops. The nature of the disloc...Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures.The annealing process made the defects develop into large dislocation loops. The nature of the dislocation loops formed after annealing was studied by the evolution of loops under in situ electron irradiation in high-voltage electron microscope.It indicated that only interstitial-type loops were observed when annealed at 550 °C and below, but vacancy-type loops started to form at the temperature higher than 600 °C. According to the previous study of our group, the presence of chromium element made the formation temperature of vacancy-type loops higher than that in pure iron. The effect of alloying elements on the formation temperature of the vacancy-type loops was discussed.展开更多
The microstructure and nano-hardness of the pure copper and oxide dispersion-strengthened（ODS） copper alloy subjected to 1.4 Me V Au ions irradiation at room temperature were investigated. After irradiation, disloca...The microstructure and nano-hardness of the pure copper and oxide dispersion-strengthened（ODS） copper alloy subjected to 1.4 Me V Au ions irradiation at room temperature were investigated. After irradiation, dislocation-loops form in both materials, while voids can only be generated in the pure copper. Compared with the irradiated pure copper, larger average diameter and lower number density of irradiation-induced dislocation-loops were detected in the ODS copper alloy, revealing that high-density dislocation and large volume of Al2O3 particles existing in the ODS copper alloy can act as effective sinks for the irradiation-induced defects. It was also detected that irradiation hardening in the ODS copper alloy is lower than that in the pure copper. The microstructure and nano-hardness results reveal that the ODS copper alloy has a better irradiation tolerance than the pure copper. In addition, the average diameter of the Al2O3 particles in the ODS copper alloy decreases after irradiation, because the Al–O chemical bonds are decomposed and the atoms are redistributed in the matrix during the irradiation process. This work reveals that the irradiation tolerance of the copper can be effectively enhanced by adding nano-sized Al2O3 particles into the matrix.展开更多
Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)...Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)up to 0.15 displacements per atom(dpa)in the Belgian reactor(BR2).The study of the microstructure of neutron-damaged samples using transmission electron microscopy(TEM)revealed visible defects with a predominance of dislocation loops.With an increase in the neutron irradiation temperature,the spatial distribution of the loops acquired pronounced inhomogeneity,and their average size moderately increased.Cavities and voids were not observed.Irradiation-induced hardening was found and a linear correlation was obtained between Vickers microhardness and nanohardness for undamaged and neutron-irradiated CVD-W samples.Irradiation of tungsten with neutrons led to a significant increase in the retention of deuterium,which accumulated mainly in vacancy-type traps.Furthermore,the influence of the columnar grain structure in low-dose neutron-irradiated tungsten seemed to be non-trivial upon deuterium retention.展开更多
The oxides formed on the surface of the alloy 690 in hydrogenated supercritical water at 400℃ for 1000 h were investigated using scanning electron microscopy,transmission electron microscopy,scanning transmission ele...The oxides formed on the surface of the alloy 690 in hydrogenated supercritical water at 400℃ for 1000 h were investigated using scanning electron microscopy,transmission electron microscopy,scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy.The oxides on me surface of the alloy 690 exhibited multi-layer structure：an outer layer consisted of granular crystallites（NiO and NiFe_2O_4） and a compact inner layer（spinel and Cr_2O_3）.Chemical analysis indicated that the outer layer was enriched in nickel but depleted in chromium,whereas the inner layer was enriched in chromium and iron but depleted in nickel.The inner layer was also characterized as layered structure by Fe-rich spinel on top of continuous Cr_2O_3 layer.Besides,Cr_2O_3 nodules were readily observed at the oxides/alloy interface.展开更多
基金the National Natural Science Foundation of China (51501097)Natural Science Foundation of Shandong Province,China (ZR2014EMP005).
文摘The formation of precipitates and their effect on mechanical properties and irradiation damage in V-4CraTi alloys have been investigated using transmission electron microscope,high-temperature tensile tests and high-voltage electron microscope (HVEM).V-4Cr-4Ti alloys were aged for 20-40 h at 873 K,and extremely fine precipitates were produced during the aging process,which coarsened with aging time.The results of high-temperature (773,873 and 973 K)tensile tests showed an increase in strength with increasing aging time (i.e:,increasing size of precipitates)while a decrease in the uniform elongation.There was evidence that presence of precipitates strengthened V-4Cr-4Ti alloys.In situ HVEM observations showed that the precipitates restricted the growth rate of dislocation loops induced during electron irradiation at 773 K.The interactions between precipitates and irradiation-induced dislocation loops were discussed.The presence of particles alleviated the increase in irradiation hardening up to an irradiation dose of 3.42 dpa (displacement per atom).The precipitates shrank in size during electron irradiation,which was due to the dissolution of constituent atoms of the precipitates into the alloy matrix.
基金supported by the National Natural Science Foundation of China(No.11275023)the National Magnetic Confinement Fusion Program(No.2011GB110004)
文摘The different influences of the general grain boundary and the twin boundary on the cavity formation were investigated in copper irradiated by helium at room temperature. Large number of the cavities with sizes smaller than 5 nm formed after irradiation, which were almost homogenously distributed inside the grains. However, the distribution of the cavities varied near the general grain boundary and the twin boundary. Cavities-depleted zone was readily observed near the general grain boundaries, which was rarely observed near the twin boundaries. Meanwhile, decoration of dense cavities within the grain boundary plane was observed. The results suggested the limited influence of the twin boundaries as the point defect sinks compared with the general grain boundaries.
基金supported by the National Natural Science Foundation of China (Grant No. 51471026)
文摘Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures.The annealing process made the defects develop into large dislocation loops. The nature of the dislocation loops formed after annealing was studied by the evolution of loops under in situ electron irradiation in high-voltage electron microscope.It indicated that only interstitial-type loops were observed when annealed at 550 °C and below, but vacancy-type loops started to form at the temperature higher than 600 °C. According to the previous study of our group, the presence of chromium element made the formation temperature of vacancy-type loops higher than that in pure iron. The effect of alloying elements on the formation temperature of the vacancy-type loops was discussed.
基金financially supported by the National Natural Science Foundation of China (Nos. 11175014, 50971030)the National Basic Research Program of China (No. 11163110)the National Magnetic Confinement Fusion Program (No. 2011GB108002)
文摘The microstructure and nano-hardness of the pure copper and oxide dispersion-strengthened（ODS） copper alloy subjected to 1.4 Me V Au ions irradiation at room temperature were investigated. After irradiation, dislocation-loops form in both materials, while voids can only be generated in the pure copper. Compared with the irradiated pure copper, larger average diameter and lower number density of irradiation-induced dislocation-loops were detected in the ODS copper alloy, revealing that high-density dislocation and large volume of Al2O3 particles existing in the ODS copper alloy can act as effective sinks for the irradiation-induced defects. It was also detected that irradiation hardening in the ODS copper alloy is lower than that in the pure copper. The microstructure and nano-hardness results reveal that the ODS copper alloy has a better irradiation tolerance than the pure copper. In addition, the average diameter of the Al2O3 particles in the ODS copper alloy decreases after irradiation, because the Al–O chemical bonds are decomposed and the atoms are redistributed in the matrix during the irradiation process. This work reveals that the irradiation tolerance of the copper can be effectively enhanced by adding nano-sized Al2O3 particles into the matrix.
基金Neutron irradiations at BR2 in SCK/CEN were carried out in the framework of MICADO project.Hot-lab experiments were conducted at the International Research Centre for Nuclear Materials Science(Oarai site),Institute for Materials Research(IMR),Tohoku University.All authors wish to thank IMR staffs Mr.K.Suzuki and T.Maniwa for their kind assistance.X.Yi acknowledges funding support from the Global Institute for Materials Research Tohoku(GIMRT)program via proposals No.19M0504,20M0502 and 202012-IRKMA-0516the National Natural Science Foundation of China via grant No.12175013J.P.Song acknowledges funding support from the National Magnetic Confinement Fusion Program of China via Grant No.2018YFE031210.
文摘Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)up to 0.15 displacements per atom(dpa)in the Belgian reactor(BR2).The study of the microstructure of neutron-damaged samples using transmission electron microscopy(TEM)revealed visible defects with a predominance of dislocation loops.With an increase in the neutron irradiation temperature,the spatial distribution of the loops acquired pronounced inhomogeneity,and their average size moderately increased.Cavities and voids were not observed.Irradiation-induced hardening was found and a linear correlation was obtained between Vickers microhardness and nanohardness for undamaged and neutron-irradiated CVD-W samples.Irradiation of tungsten with neutrons led to a significant increase in the retention of deuterium,which accumulated mainly in vacancy-type traps.Furthermore,the influence of the columnar grain structure in low-dose neutron-irradiated tungsten seemed to be non-trivial upon deuterium retention.
文摘The oxides formed on the surface of the alloy 690 in hydrogenated supercritical water at 400℃ for 1000 h were investigated using scanning electron microscopy,transmission electron microscopy,scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy.The oxides on me surface of the alloy 690 exhibited multi-layer structure：an outer layer consisted of granular crystallites（NiO and NiFe_2O_4） and a compact inner layer（spinel and Cr_2O_3）.Chemical analysis indicated that the outer layer was enriched in nickel but depleted in chromium,whereas the inner layer was enriched in chromium and iron but depleted in nickel.The inner layer was also characterized as layered structure by Fe-rich spinel on top of continuous Cr_2O_3 layer.Besides,Cr_2O_3 nodules were readily observed at the oxides/alloy interface.
