摘要
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.
γ'-Ni_(3)Al相在高温下的反常流变行为与1/2<110>{111}超级部分位错的交滑移密切相关。沿最低能量路径获得的广义堆垛层错能曲线(即Γ面)可以提供大量有关位错形核和运动的信息。采用第一性原理计算,研究Re、W、Mo、Ta、Ti单掺杂与双掺杂对γ'-Ni_(3)Al相Γ面和理想剪切强度τ_(max)的影响。与Re掺杂的情形类似,W在堆垛层错处的Suzuki偏聚可阻止1/6<112>{111}Shockley部分位错的运动和促进1/2<110>{111}超级部分位错的交滑移。当Re被W部分取代时,γ_(APB)^(111)/γ_(APB)^(001)的降低表明γ'相在高温下的反常流变行为不如双Re掺杂,但τ_(max)的增加却表明镍基单晶高温合金的蠕变断裂强度在一定程度上可从中受益,尤其是Re和W在Al−Al位的共偏聚。当点缺陷X1_(Al)和X2_(Al)之间的相互作用采用关联能函数ΔE^(X1_(Al)+X2_(Al))(d)来表征时,无论是吸引还是排斥,强关联都不利于γ'相屈服强度的提高。
基金
the financial supports from the National Natural Science Foundation of China(Nos.51871096,52071136).
