The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is cru...The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is crucial for the mechanism of material degradation. The novel diffusion behavior of He has been reported by molecular dynamics（MD） simulation for the bulk hcp-Ti system and the system with grain boundary（GB）. It is observed that the diffusion of He in the bulk hcp-Ti is significantly anisotropic（the diffusion coefficient of the [0001] direction is higher than that of the basal plane）,as represented by the different migration energies. Different from convention, the GB accelerates the diffusion of He in one direction but not in the other. It is observed that a twin boundary（TB） can serve as an effective trapped region for He.The TB accelerates diffusion of He in the direction perpendicular to the twinning direction（TD）, while it decelerates the diffusion in the TD. This finding is attributable to the change of diffusion path caused by the distortion of the local favorable site for He and the change of its number in the TB region.展开更多
The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic steel,which is a candidate structural material for fusion reactors.In order to eluc...The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic steel,which is a candidate structural material for fusion reactors.In order to elucidate the susceptibility of different grain boundaries(GBs)to helium-induced embrittlement,the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic(bcc)iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods.The results indicate that in the absence of helium bubbles,the GBs studied here can be classified into two distinct categories:brittle GBs and ductile GBs.The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms,including the Bain/Burgers path phase transition and deformation twinning,in which the Bain path phase transition is the most dominant plastic deformation mechanism.However,the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs,resulting in a significant decrease in elongation at fractures.For bubble-decorated GBs,the ultimate tensile strength increases with the increase in the misorientation angle.Interestingly,the coherent twin boundary∑3{112}was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.展开更多
We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an i...We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an interstitial helium atom to the grain boundary plane is the strongest among all sites around the plane. The He_N defect is much more stable in nickel bulk than in the grain boundary plane. Besides, the binding energy of an interstitial helium atom to a vacancy is stronger than that to a grain boundary plane. The binding strength between the grain boundary and the HeN defect increases with the defect size. Moreover, the binding strength of the HeN defect to the Σ3（112）[110] grain boundary becomes much weaker than that to other grain boundaries as the defect size increases.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51501119)the Scientific Research Starting Foundation for Younger Teachers of Sichuan University,China(Grant No.2015SCU11058)+1 种基金the National Magnetic Confinement Fusion Science Program of China(Grant No.2013GB109002)the Cooperative Research Project "Research of Diffusion Behaviour of He in Grain Boundary of HCP-Titanium",China
文摘The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is crucial for the mechanism of material degradation. The novel diffusion behavior of He has been reported by molecular dynamics（MD） simulation for the bulk hcp-Ti system and the system with grain boundary（GB）. It is observed that the diffusion of He in the bulk hcp-Ti is significantly anisotropic（the diffusion coefficient of the [0001] direction is higher than that of the basal plane）,as represented by the different migration energies. Different from convention, the GB accelerates the diffusion of He in one direction but not in the other. It is observed that a twin boundary（TB） can serve as an effective trapped region for He.The TB accelerates diffusion of He in the direction perpendicular to the twinning direction（TD）, while it decelerates the diffusion in the TD. This finding is attributable to the change of diffusion path caused by the distortion of the local favorable site for He and the change of its number in the TB region.
基金supported by the National Natural Science Foundation of China(Nos.12175231 and 11805131)Anhui Natural Science Foundation of China(No.2108085J05)+1 种基金the National Key Research and Development Plan of China(No.2018YFE0307101)the Collaborative Innovation Program of the Hefei Science Center,CAS(Nos.2021HSC-CIP020 and 2022HSC-CIP009)。
文摘The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic steel,which is a candidate structural material for fusion reactors.In order to elucidate the susceptibility of different grain boundaries(GBs)to helium-induced embrittlement,the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic(bcc)iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods.The results indicate that in the absence of helium bubbles,the GBs studied here can be classified into two distinct categories:brittle GBs and ductile GBs.The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms,including the Bain/Burgers path phase transition and deformation twinning,in which the Bain path phase transition is the most dominant plastic deformation mechanism.However,the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs,resulting in a significant decrease in elongation at fractures.For bubble-decorated GBs,the ultimate tensile strength increases with the increase in the misorientation angle.Interestingly,the coherent twin boundary∑3{112}was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.
基金Project supported by the Program of International S&T Cooperation,China(Grant No.2014DFG60230)the National Basic Research Program of China(Grant No.2010CB934504)+2 种基金Strategically Leading Program of the Chinese Academy of Sciences(Grant No.XDA02040100)the Shanghai Municipal Science and Technology Commission,China(Grant No.13ZR1448000)the National Natural Science Foundation of China(Grant Nos.91326105 and 21306220)
文摘We investigated the effect of grain boundary structures on the trapping strength of HeN（N is the number of helium atoms） defects in the grain boundaries of nickel. The results suggest that the binding energy of an interstitial helium atom to the grain boundary plane is the strongest among all sites around the plane. The He_N defect is much more stable in nickel bulk than in the grain boundary plane. Besides, the binding energy of an interstitial helium atom to a vacancy is stronger than that to a grain boundary plane. The binding strength between the grain boundary and the HeN defect increases with the defect size. Moreover, the binding strength of the HeN defect to the Σ3（112）[110] grain boundary becomes much weaker than that to other grain boundaries as the defect size increases.
