First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（G...First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（GB）. The negative segregation energy of a P atom proves that a P atom can easily segregate in the Ni Al GB. The atomic configuration and formation energy of the P atom in the Ni Al GB demonstrate that the P atom tends to occupy an interstitial site or substitute a Al atom depending on the Ni/Al atoms ratio. The P atom is preferable to staying in the Ni-rich environment in the Ni Al GB forming P–Ni bonds. Both of the charge density and the deformation charge imply that a P atom is more likely to bond with Ni atoms rather than with Al atoms. The density of states further exhibits the interactions between P atom and Ni atom, and the orbital electrons of P, Ni and Al atoms all contribute to P–Ni bonds in the Ni Al GB. It is worth noting that the P–Ni covalent bonds might embrittle the Ni Al GB and weakens the plasticity of the Ni Al intermetallics.展开更多
The design of high irradiation-resistant materials is very important for the development of next-generation nuclear reactors. Grain boundaries acting as effective defect sinks are thought to be able to moderate the de...The design of high irradiation-resistant materials is very important for the development of next-generation nuclear reactors. Grain boundaries acting as effective defect sinks are thought to be able to moderate the deterioration of mechanical behaviors of irradiated materials, and have drawn increasing attention in recent years. The study of the effect of grain boundaries on the mechanical behaviors of irradiated materials is a multi-scale problem. At the atomic level, grain boundaries can effectively affect the production and formation of irradiation-induced point defects in grain interiors, which leads to the change of density, size distribution and evolution of defect clusters at grain level. The change of microstructure would influence the macroscopic mechanical properties of the irradiated polycrystal. Here we give a brief review about the effect of grain boundaries on the mechanical behaviors of irradiated metals from three scales: microscopic scale, mesoscopic scale and macroscopic scale.展开更多
In this work,we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy,which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K co...In this work,we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy,which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K compared to its counterparts at 298 K.The deformation mechanisms responsible for the excellent strength-ductility synergy and extraordinary strain hardening capacity at cryogenic temperature were elucidated through a combined experimental and simulation study.The results reveal the presence of numerous slip traces and microbands throughout grain surfaces during deformation at 298 K,whereas at 77 K,vague grain surfaces dominate,indicating the simultaneous operation of multiple slip systems.Transmission electron microscopy(TEM)analysis using the two-beam diffraction technique demonstrates the presence of dislocations with several different Burgers vectors inside a grain at cryogenic temperature,confirming the activation of multiple slip systems.The accumulation of dislocations facilitated by these multiple slip systems,combined with the high dislocation density,contributes to strain hardening and remarkable uniform elongation at 77 K.A modified dislocation density-based crystal plasticity model,incorporating the effect of grain boundary hardening(GBH)and temperature,was developed to gain a better understanding of the underlying mechanisms governing alloy’s strength and plasticity.The GBH effect significantly enhances statistically stored dislocation(SSD)density and screw dislocation proportion,which promote homogeneous deformation and enhance strain hardening capacity at cryogenic temperature.These findings deepen the understanding of plastic deformation at cryogenic temperatures and pave the way for the development of ultrahigh-performance metallic materials for cryogenic applications.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51201181)the Scientific Research Fund of Civil Aviation University of China(Grant No.08QD14X)
文摘First-principles calculations based on the density functional theory（DFT） and ultra-soft pseudopotential are employed to study the atomic configuration and charge density of impurity P in Ni Al Σ5 grain boundary（GB）. The negative segregation energy of a P atom proves that a P atom can easily segregate in the Ni Al GB. The atomic configuration and formation energy of the P atom in the Ni Al GB demonstrate that the P atom tends to occupy an interstitial site or substitute a Al atom depending on the Ni/Al atoms ratio. The P atom is preferable to staying in the Ni-rich environment in the Ni Al GB forming P–Ni bonds. Both of the charge density and the deformation charge imply that a P atom is more likely to bond with Ni atoms rather than with Al atoms. The density of states further exhibits the interactions between P atom and Ni atom, and the orbital electrons of P, Ni and Al atoms all contribute to P–Ni bonds in the Ni Al GB. It is worth noting that the P–Ni covalent bonds might embrittle the Ni Al GB and weakens the plasticity of the Ni Al intermetallics.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11225208 and 11521202)
文摘The design of high irradiation-resistant materials is very important for the development of next-generation nuclear reactors. Grain boundaries acting as effective defect sinks are thought to be able to moderate the deterioration of mechanical behaviors of irradiated materials, and have drawn increasing attention in recent years. The study of the effect of grain boundaries on the mechanical behaviors of irradiated materials is a multi-scale problem. At the atomic level, grain boundaries can effectively affect the production and formation of irradiation-induced point defects in grain interiors, which leads to the change of density, size distribution and evolution of defect clusters at grain level. The change of microstructure would influence the macroscopic mechanical properties of the irradiated polycrystal. Here we give a brief review about the effect of grain boundaries on the mechanical behaviors of irradiated metals from three scales: microscopic scale, mesoscopic scale and macroscopic scale.
基金supported by the National Natural Science Foundation of China(Nos.92263201,51927801,52001160,and 52205378)the National Key Research&Development Plan(Nos.2020YFA0405900 and 2019YFA0708801)Natural Science Foundation of Jiangsu Province(No.BK20202010).
文摘In this work,we investigated the mechanical properties and corresponding deformation mechanisms of an Al1Mg0.4Si alloy,which exhibited significantly higher strength and outstanding strain hardening capacity at 77 K compared to its counterparts at 298 K.The deformation mechanisms responsible for the excellent strength-ductility synergy and extraordinary strain hardening capacity at cryogenic temperature were elucidated through a combined experimental and simulation study.The results reveal the presence of numerous slip traces and microbands throughout grain surfaces during deformation at 298 K,whereas at 77 K,vague grain surfaces dominate,indicating the simultaneous operation of multiple slip systems.Transmission electron microscopy(TEM)analysis using the two-beam diffraction technique demonstrates the presence of dislocations with several different Burgers vectors inside a grain at cryogenic temperature,confirming the activation of multiple slip systems.The accumulation of dislocations facilitated by these multiple slip systems,combined with the high dislocation density,contributes to strain hardening and remarkable uniform elongation at 77 K.A modified dislocation density-based crystal plasticity model,incorporating the effect of grain boundary hardening(GBH)and temperature,was developed to gain a better understanding of the underlying mechanisms governing alloy’s strength and plasticity.The GBH effect significantly enhances statistically stored dislocation(SSD)density and screw dislocation proportion,which promote homogeneous deformation and enhance strain hardening capacity at cryogenic temperature.These findings deepen the understanding of plastic deformation at cryogenic temperatures and pave the way for the development of ultrahigh-performance metallic materials for cryogenic applications.
