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利用电子显微技术研究了Co-12Al-10W三元高温合金在热处理过程中的微观组织转变过程。结果表明,铸态合金的显微组织存在初生Co Al相。经过1300℃×8 h固溶处理后,初生Co Al相完全固溶,并析出μ相。随后在900℃时效处理过程中,γ和γ’相两相共格结构在50 h后出现,γ’相的尺寸随时间的延长不断增大。在时效处理初期,析出相主要为μ相;随着时效时间的延长,部分μ相边缘出现了DO19相;而时效时间进一步延长至600 h后,大量的μ相边缘出现了DO19相和B2相,同时在晶内出现了大量的针状B2相。电子衍射谱的分析表明,μ相、DO19相、B2相和γ’相之间存在着特定的取向关系为[111]_(B2)//[110]_(γ’),(011)_(B2)//(111)_(γ’),[001]_μ//[110]_(B2)//[001]_(DO19),(112)_(B2)//(100)_μ//(100)_(DO19),(110)_(B2)//(027)_μ//(010)_(DO19)。这些特殊的取向关系归结于析出相之间的结构关联性,而相转变则由W元素在时效处理过程中的扩散作用造成。
The microstructure transition of Co-12Al-10W ternary superalloy during heat treatment was studied by electron microscopy. The results show that there is primary Co Al phase in the as-cast alloy microstructure. After 1300 ℃ × 8 h solution treatment, the primary Co Al phase completely dissolved and precipitated μ phase. Subsequently, during the aging treatment at 900 ℃, the two-phase structure of γ and γ ’phases appeared after 50 h, and the size of γ’ phase increased with time. In the initial stage of aging treatment, the precipitates were mainly μ phase. With the extension of aging time, the DO19 phase appeared at the edge of some μ phases. When the aging time was further extended to 600 hours, DO19 and B2 , While in the crystal appeared a lot of needle-like B2 phase. The results of electron diffraction showed that the specific orientations of μ phase, DO19 phase, B2 phase and γ ’phase were [111] _ (B2) // [110] _ (γ’), (B2) // (111) _ (γ ’), [001] _μ // [110] _ (B2) // [001] _ (DO19), (112) // (100) _ (DO19), (110) _ (B2) // (027) _μ // (010) _ (DO19). These special orientation relationships are attributed to the structural correlation between the precipitates, while the phase transition is caused by the diffusion of the W element during the aging process.