Effect of precipitation phase on the flow behavior of a nickel-based superalloy during compressive deformation

Nickel-based superalloys have become indispensable in micro-forming processes owing to their outstanding mechanical properties. The size effect significantly impacts the formability of components at the mesoscopic scale, resulting in compression deformation behaviors distinct from those observed at the macroscopic scale. The classical Hall-Petch formula can hardly express this phenomenon precisely. This study conducted compression tests of a nickel-based superalloy at the mesoscopic scale, exploring the role of the feature size (specifically, the ratio of sample diameter to grain size, D/d) and the precipitation phase on the plastic deformation behavior. The results show that increasing feature size of samples as well as particle size and volume fraction of gamma ' and gamma" phases enhance the flow stress of the superalloy. When the feature size exceeds 8.6, the flow stress decreases with decreasing feature size. However, when the feature size is below 8.6, the flow stress increases with decreasing feature size. A model is proposed to comprehensively explain the size effect and the precipitation phase on compressive flow stress. The surfaces of samples experience inhomogeneous deformation during compressive deformation. The trend towards inhomogeneous deformation has become more pronounced as feature size decreases. Furthermore, the increase in particle size and volume fracture of gamma ' and gamma" phases limits the inhomogeneous deformation of the sample surface.