Abstract
The effects of the mixed-grain microstructure on mechanical property of nickel-based superalloy GH4720Li were studied by optical microscope (OM), field emission scanning electron microscope (FE-SEM) and series properties tests. The results show that the tensile strength and yield strength of structure B (partial mixed crystal+primarny y' phase) at 650 degrees C for specimens are reduced compared with those of structure A (uniform fine grain+primary y' phase). The tensile strength of structure C (completely mixed crystal+primary y' phase) drops rapidly with the increase of volume fraction of coarse grain. Furthmore, the deformation mechanism of superalloys at high temperature is not the same under different stress-rupture test conditions. Under the condition of 730 degrees C/530 MPa, the stress -rupture life increases with the increase of the volume fraction of coarse grain for the reason that grain boundary sliding mechanism plays an important role. While the major deformation mechanisms is found to be disloc