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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 TEM analysis of the microstructure of two GH36 superalloys undergone different regimes of heat treatment was conducted. The precipitates were identified as VC, M_(23)C_6 and NbC. The orientation relationship between the precipitates and γ matrix is shown as follows:[011]_(v C)//[011]_M//[011]_(M_(23)C_6)(111)_(v C)//(111)_M//(111)_(M_(23)C_6)(200)_(v C)//(200)_M//(200)_(M_(23)C_6)After normal heat treatment, the VC precipitates and distributes as fine dispersed particles of size from several to ten odd nm, and minimum ones are down to 2.8 nm alone examined by Moire pattern. The VC may coagulate and grow in a few nm larger and more M_(23)C_6 may precipitate along grain boundary after superimposed aging at elevated temperature. This microstructure and grain boundary precipitation may reduce the yield and stress rupture strengthes of the alloy, but improve the notch sensitivity of stress rupture test.