The site occupancy behavior of ternary alloying elements inγ'-Ni3Al(a key strengthening phase of commercial Ni-based single-crystal superalloys)can change with temperature and alloy composition owing to the effec...The site occupancy behavior of ternary alloying elements inγ'-Ni3Al(a key strengthening phase of commercial Ni-based single-crystal superalloys)can change with temperature and alloy composition owing to the effect of entropy.Using a total-energy method based on density functional theory,the dependence of tensile and shear behaviors on the site preference of alloying elements inγ'-Ni3Al were investigated in detail.Our results demonstrate that Fe,Ru,and Ir can significantly improve the ideal tensile and shear strength of theγ'phase when occupying the Al site,with Ru resulting in the strongest enhancement.In contrast,elements with fully filled d orbitals(i.e.,Cu,Zn,Ag,and Cd)are expected to reduce the ideal tensile and shear strength.The calculated stress-strain relationships of Ni3Al alloys indicate that none of the alloying elements can simultaneously increase the ideal strength of theγ'phase for both Ni1-site and Ni2-site substitutions.In addition,the charge redistribution and the bond length of the alloying elements and host atoms during the tensile and shear processes are analyzed to unveil the underlying electronic mechanisms.展开更多
The electrodeposited Y2O3-dispersedγ-Ni+γ′-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed Al microparticles in Ni matrix into Ni3Al by vacuum an...The electrodeposited Y2O3-dispersedγ-Ni+γ′-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed Al microparticles in Ni matrix into Ni3Al by vacuum annealing at 800℃for 3 h. For comparison,Y2O3-freeγ-Ni+γ′-Ni3Al coatings with a similar Al content were also prepared by vacuum annealing the electrodeposited microparticle-dispersed composite coatings of Ni-Al under the same condition.SEM and TEM characterizations show that the electrodeposited Y2O3-dispersedγ+γ′coatings exhibit finer grains,a more homogeneous distribution ofγ′,and a narrowedγ′phase spacing compared with the electrodeposited Y 2 O3-freeγ+γ′coatings.The oxidation at 1 000℃shows that the addition of Y2O3 significantly improves the oxidation resistance of the electrodepositedγ+γ′coatings.The effect of Y2O3 particles on the microstructure and oxidation behavior of the electrodepositedγ+γ′coatings was discussed in detail.展开更多
The anomalous flow behavior of γ'-Ni_(3)Al phases at high temperature is closely related to the cross-slip of 1/2<110>{111}super-partial dislocations.Generalized stacking fault energy curves(i.e.,Γ-surface...The anomalous flow behavior of γ'-Ni_(3)Al phases at high temperature is closely related to the cross-slip of 1/2<110>{111}super-partial dislocations.Generalized stacking fault energy curves(i.e.,Γ-surfaces)along the lowest energy path can provide a great deal of information on the nucleation and movement of dislocations.With the first-principles calculation,the interplay between Re and W,Mo,Ta,Ti doped at preferential sites and their synergetic influence on Γ-surfaces and ideal shear strength(τ_(max))in γ'-Ni_(3)Al phases are investigated.Similar to single Re-addition,the Suzuki segregation of W at stacking faults is demonstrated to enable to impede the movement of 1/6<112>{111} Shockley partial dislocations and promote the cross-slip of 1/2<110>{111}super-partial dislocations.With the replacement of a part of Re by W,a decreased γ_(APB)^(111)/γ_(APB)^(001) indicates that the anomalous flow behavior of γ'phases at high temperature is not as excellent as the double Re-addition,but an increasedτmax means that the creep rupture strength of Ni-based single crystal superalloys can be benefited from this replacement to some extent,especially in the co-segregation of Re and W at Al−Al sites.As the interaction between X1_(Al) and X2_(Al) point defects is characterized by an correlation energy function ΔE^(X1_(Al)+X2_(Al))(d),it is found that both strong attraction and strong repulsion are unfavarable for the improvement of yield strengths of γ'phase.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11804057)the Natural Science Foundation of Guangdong Province,China(Grant No.2017B030306003)the National Key Research and Development Program of China(Grant No.2017YFB0701500).
文摘The site occupancy behavior of ternary alloying elements inγ'-Ni3Al(a key strengthening phase of commercial Ni-based single-crystal superalloys)can change with temperature and alloy composition owing to the effect of entropy.Using a total-energy method based on density functional theory,the dependence of tensile and shear behaviors on the site preference of alloying elements inγ'-Ni3Al were investigated in detail.Our results demonstrate that Fe,Ru,and Ir can significantly improve the ideal tensile and shear strength of theγ'phase when occupying the Al site,with Ru resulting in the strongest enhancement.In contrast,elements with fully filled d orbitals(i.e.,Cu,Zn,Ag,and Cd)are expected to reduce the ideal tensile and shear strength.The calculated stress-strain relationships of Ni3Al alloys indicate that none of the alloying elements can simultaneously increase the ideal strength of theγ'phase for both Ni1-site and Ni2-site substitutions.In addition,the charge redistribution and the bond length of the alloying elements and host atoms during the tensile and shear processes are analyzed to unveil the underlying electronic mechanisms.
基金Project(06-13)supported by the Scientific Research Startup Foundation of Heilongjiang University of Science and Technology,China
文摘The electrodeposited Y2O3-dispersedγ-Ni+γ′-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed Al microparticles in Ni matrix into Ni3Al by vacuum annealing at 800℃for 3 h. For comparison,Y2O3-freeγ-Ni+γ′-Ni3Al coatings with a similar Al content were also prepared by vacuum annealing the electrodeposited microparticle-dispersed composite coatings of Ni-Al under the same condition.SEM and TEM characterizations show that the electrodeposited Y2O3-dispersedγ+γ′coatings exhibit finer grains,a more homogeneous distribution ofγ′,and a narrowedγ′phase spacing compared with the electrodeposited Y 2 O3-freeγ+γ′coatings.The oxidation at 1 000℃shows that the addition of Y2O3 significantly improves the oxidation resistance of the electrodepositedγ+γ′coatings.The effect of Y2O3 particles on the microstructure and oxidation behavior of the electrodepositedγ+γ′coatings was discussed in detail.
基金the financial supports from the National Natural Science Foundation of China(Nos.51871096,52071136).
文摘The anomalous flow behavior of γ'-Ni_(3)Al phases at high temperature is closely related to the cross-slip of 1/2<110>{111}super-partial dislocations.Generalized stacking fault energy curves(i.e.,Γ-surfaces)along the lowest energy path can provide a great deal of information on the nucleation and movement of dislocations.With the first-principles calculation,the interplay between Re and W,Mo,Ta,Ti doped at preferential sites and their synergetic influence on Γ-surfaces and ideal shear strength(τ_(max))in γ'-Ni_(3)Al phases are investigated.Similar to single Re-addition,the Suzuki segregation of W at stacking faults is demonstrated to enable to impede the movement of 1/6<112>{111} Shockley partial dislocations and promote the cross-slip of 1/2<110>{111}super-partial dislocations.With the replacement of a part of Re by W,a decreased γ_(APB)^(111)/γ_(APB)^(001) indicates that the anomalous flow behavior of γ'phases at high temperature is not as excellent as the double Re-addition,but an increasedτmax means that the creep rupture strength of Ni-based single crystal superalloys can be benefited from this replacement to some extent,especially in the co-segregation of Re and W at Al−Al sites.As the interaction between X1_(Al) and X2_(Al) point defects is characterized by an correlation energy function ΔE^(X1_(Al)+X2_(Al))(d),it is found that both strong attraction and strong repulsion are unfavarable for the improvement of yield strengths of γ'phase.
