单晶高温合金小角度晶界组织演化

Microstructure Evolution of Low Angle Grain Boundaries in Single Crystal Superalloy

研究了单晶高温合金不同状态小角度晶界组织的演变规律。从小角度晶界附近局部凝固热力学状态的角度,分析了小角度晶界铸态组织的形成。结果发现,由于整个单晶铸件由一个晶粒组成,连续分布在共晶中的γ′相不能额外形核,而是以小角度晶界一侧晶体为基长大,同时为了避免出现额外相界面,共晶中的γ相以晶界另一侧晶体为基长大,因而含有连续共晶的小角度晶界两侧倾向于形成不同的相。由于单晶高温合金基体相γ和析出相γ′粒子之间存在严格的晶体取向关系,以及在小角度晶界的限制下,标准热处理态合金中晶界处的γ′相粒子通常为不完整立方体。由于不同相之间严格取向关系作用,同时由于γ′相的体积分数明显占优,合金小角度晶界两侧同为γ′相的几率较高。

The microstructure evolution of low angle grain boundaries（LABs）in single crystal superalloy was described.The thermodynamic solidification state in the vicinity of LAB was analyzed.The continuously distributed phaseγ′in the eutectics on the LAB is grown on the one side of the LAB because the whole castings consists of one grain.At the same time,theγphase in the eutectics is grown on the other side to avoid the presence of additionalγ′/γinterface,resulting in that the phase on the one side of LAB different from that on the other side.Both sides of LABs tend to beγ′phase because there is more volume fraction ofγ′phase and theγ′phase can＇t change its shape to adopt the LAB based on the rigid orientation relationship betweenγandγ′.