Abstract: By TEM analysis,the microstructure of the hole expansion strengthened layer of high temperature alloy GH169 was studied. The results revealed that the dislocations show planar and cross-slip characteristics. With increasing the distance from the hole edge, the slip bands were getting obscure, while the diameter of the dislocation cell increased a little. Few of twins in the strengthened layer were present,and thus the twinning was not the main deformation mode in the alloy. It was observed that many dislocations were tangled around the γ',γ" and δ phases in the regions with high density of dislocations. According to the experimental results,it was shown that the alloy GH169 has a strengthened layer with nearly 3 mm depth from the hole edge.

Key words: heat resistant, alloy hole expansion, microstructure