固溶温度对单晶镍基合金成分偏析和蠕变行为的影响

Influence of solution temperature on composition segregation and creep behaviors of single crystal nickel based superalloy

通过对不同温度固溶处理合金枝晶干/间区域进行成分分析、蠕变性能测试及组织形貌观察,研究固溶温度对一种无Re单晶镍基合金成分偏析和蠕变行为的影响。结果表明:经不同温度固溶处理后,合金中枝晶干/间区域具有不同的偏析程度,随固溶温度提高,元素偏析程度降低,可明显提高合金的蠕变抗力和延长蠕变寿命。800℃蠕变期间,合金中γ′相仅形成串状结构,未形成完全筏状组织。合金在中温蠕变期间的变形机制是位错在基体中滑移和剪切γ′相,其中,在基体中发生大量位错的单取向、双取向滑移,可产生形变硬化作用,阻碍位错运动,加之γ′/γ两相共格界面的应力场作用,可抑制位错剪切进入γ′相,是使合金在稳态蠕变期间保持较低应变速率的主要原因。

By means of solution treatment at various temperatures, creep properties measurement and microstructure observation, the effects of heat treatment on the composition segregation and creep properties of a single crystal nickel-based superalloy were investigated. The results show that the various segregation extents of the elements display in the interdendrite/dendrite regions of the alloy solution-treated at different temperatures, and the segregation extent of the elements is improved with the increase of the solution temperature, which may obviously improve the creep resistance and prolong the creep life of the alloy. During the creep at 800 ℃, the γ′ phase in the alloy only forms bunch-like structure, and no fully rafting structure forms. The deformation mechanisms of the alloy during creep at intermediate temperature/higher stress are the dislocations slipping in the matrix and shearing into γ′ phase. Thereinto, significant amount of dislocations with single oriented and double oriented slipping features activated in the γ matrix may hinder dislocation motion due to the effect of deformation strengthening, and the stress field effect in the coherent interface of γ′/γ phase can restrain dislocation shearing into γ′ phase, which is thought to be the main reason why the alloy keeps a lower strain rate during steady state creep.