Crystal Plastic Theory And Its Application On Nickel-based Single And Bicrystal Superalloys

Nickel-based directional solidification superalloys and single crystal superalloys are widely used in advanced aero-engines, because of their excellent mechanical properties at high temperature. However, the anisotropic mechanical properties of the single crystal material make a great deal of difficulties on the development and the application of turbine blades. So, it is necessary to found a new anisotropic elasto-plastic and visco-plastic constitutive model and life predicted model to apply anisotropic single crystal material adequately, analyze and predict the strength and life of single crystal and improve the mechanic performance of domestic areo-engine.In this paper, the fundamental equation of crystallographic plastic theory and its finite element program is proposed, firstly. Further, the elasto-plastic stress and creep properties of two kinds of bicrystals with a void and without a void in grain boundary is analyzed by the crystallographic finite element method. Finally, the fracture behaviors of compact tension specimens made of nickel-based single crystal superalloys DD3 has been studied by experiments and finite element method. The main works are as follows:1. Based on finite deformation crystallographic constitutive model, Tangent stiffness type methods for rate dependent was employed, A rate-dependent constitutive model for single crystals was implemented into the user subroutine of the commercial software ABAQUS. The slip plane and slip direction of three slip systems that may be activated and movement in face-centered cubic crystal are given in second chapter.2. The equivalent stress and resolved shear stress fields of bicrystals with a void and without a void in the grain boundaries (GBs) are studied, taking the perpendicular and parallel grain boundary relative to the tensile axis into considered. There is a high stress gradient and stress concentration near the grain boundary. The features of stress concentrations are dependent on the crystallographic orientation of the two grains. At the same loading parameter, the activating law of the slip systems...