Anisotropy of Poisson’s ratio of a Ni Base Single Crystal Superalloy

Abstract:

The anisotropy of Poisson’s ratio of single crystal superalloy is essential to understand its mechanical behavior, e.g. calculating the contact stress between blade tenon and turbine disc. However, it’s difficult to determine the Poisson’s ratio of single crystal superalloy of every orientation. In this paper, one simple experimental method is employed to measure the stiffness constants and then the Poisson’s ratio of different orientation is calculated. The slabs of a third generation single crystal superalloy in two orientations á001?á100? and á011?á110? are prepared by seeding technique in Bridgman method. The Young’s modulus and shear modulus of the first specimen and the shear modulus of the second specimen are measured by resonance method from room temperature to 1100 ℃. The three stiffness constants C11, C12 and C44 of this superalloy are calculated from the measured moduli. The Poisson’s ratio in any orientation can be calculated based on the stiffness constants. Further, the 3D distribution map of maximum and minimum of Poisson’s ratio of every primary orientation can be drawn, so the distribution feature of Poisson’s ratio in 3D space can be acquired conveniently. When the primary orientations are along á001? and á111?, the Poisson’s ratio in plane is isotropy with secondary orientation. When the primary orientation is along á011?, the Poisson’s ratio demonstrates significant anisotropy with secondary orientation, the Poisson’s ratio reach minimum with secondary orientation á110? with negative value, while maximum is obtained in secondary orientation á100?.

Key words:single crystal superalloy; stiffness constant; anisotropy; Poisson’s ratio; crystal orientation