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使用薄膜TEM(透射电镜)直接观察了成分相近但热处理制度不同的两个炉号GH36合金的显微组织,使用SAD(选区电子衍射)和DF(暗场)技术做物相分析。结果表明,合金经正常热处理后析出细小弥散分布的VC,尺寸约为几nm至十几nm,由Moire干涉纹计算出最小的VC颗粒尺寸只有2.8nm。此外还有M_(23)C_6和NbC。其中VC和M_(23)C_6与合金基体的取向关系是[011]_(VC)//[11]_M//[011]_(M_(23)C_6),(111)_(VC)//(111)_M//(111)_(M_(23)C_6),(200)_(VC)//(200)_M//(200)_(M_(23)C_6)。通过补充时效后合金中VC颗粒聚集长大,晶界析出的M_(23)C_6更多,这种组织及晶界状态有利于改善合金的持久缺口敏感性。
The microstructures of GH36 alloy with similar composition but different heat treatment regimes were directly observed by TEM (Transmission Electron Microscopy), and phase analysis was performed using SAD (selective area electron diffraction) and DF (dark field) techniques. The results show that after the normal heat treatment, the alloy precipitates small and diffuse VC with size of about a few nm to ten nm and the smallest VC particle size calculated by Moire interference pattern is only 2.8 nm. There are also M_ (23) C_6 and NbC. The orientation relationship between VC and M_ (23) C_6 and the alloy matrix is [011] _ (VC) // [11] _M // [011] _ (M_ (23) C_6), (111) _ / (111) _M // (111) _ (M_ (23) C_6), (200) _ (VC) // (200) _M // (200) _ (M_ (23) C_6). By adding the VC particles in the alloy after aging, the more M_ (23) C_6 precipitated in the grain boundaries, which is beneficial to the improvement of the permanent notch sensitivity of the alloy.