FGH96合金固相扩散连接界面组织与失效机制

对原始状态分别为锻态、固溶态和半时效态的FGH96合金固相扩散连接界面显微组织进行表征，并对连接界面的拉伸性能进行测试，对失效行为进行研究。结果表明，锻态、固溶态和半时效态试样经固相扩散连接后界面均实现了良好的冶金结合，连接界面无孔洞和缝隙等缺陷。锻态试样界面扩散更为充分，组织过渡更为平缓；固溶态和半时效态试样界面存在明显的连接影响区。锻态试样经固相扩散连接和标准热处理后，二次γ?相细小、均匀且呈典型椭球状；固溶态和半时效态试样因固相扩散连接热循环的作用导致γ?相发生长大和分化。二次γ?相尺寸及形貌的不同决定了界面区域性能水平的差异。电子背散射衍射测试结果表明，连接界面处大晶粒的择优取向为{100}，距离固相扩散连接界面越近，晶粒的择优取向越明显。拉伸试验结果表明，锻态试样经固相扩散连接和标准热处理后，连接界面处的强度达到基体强度的99%以上。拉伸裂纹主要萌生于连接界面大晶粒及γ?相粗化聚集区域，体现为穿晶的韧窝型断裂。

Microstructure and failure mechanism of FGH96 solid-state diffusion bonding interface

The microstructure on the solid-state diffusion bonding interfaces of the initially as-forged, as-solution, and sub-aging FGH96 was characterized, the tensile properties of the bonding interfaces were tested, and the failure behavior was studied. It is found that the good metallurgical bonding is achieved at the bonding interfaces of all the three primitive state specimens after the solid-state diffusion, and no cracks and cavities are found. The interfaces of the as-forged specimens show more sufficient diffusion of elements and smoother transition of microstructure, while the interfaces of both the as-solution and sub-aging specimens exhibit an obvious bonding effecting zone. After the solid-state diffusion bonding and the standard heat treatment, the second γ? phases in the as-forged specimens are fine, uniform, and spherical. However, the second γ? phases in the as-solution and sub-aging specimens grow up and split up because of the solid-state diffusion bonding thermal cycle. Different morphology of the second γ? phases causes the difference of properties in the bonding interface regions. Results of the electron backscattered diffraction (EBSD) show that the preferred orientation of large grains is {100}, and the grain orientation is more obvious as the closer distance to the solid diffusion interface. The tensile test results show that the strength at the interfaces of the forged specimens after the solid-state diffusion bonding and the standard heat treatment is more than 99% of that of the matrix. The tensile cracks mainly initialize from the aggregated area of the large grains and the coarse γ? phases, which show the transgranular dimple fracture behavior.