Numerical investigation of deformation behavior of TiAl alloy with different duplex microstructures using a two-scale FE model

Abstract

In this work a micromechanical model with a two-scale FE description has been used to investigate the room temperature deformation behavior of niobium-containing two-phase TiAl alloy. A polycrystal with duplex microstructure consisting of globular and lamellar grains is modeled with 3D unit cells that take into account specific volume fractions and orientations of the grains. The globular unit cell is described by representative volume elements of γ-phases whereas the lamellar unit cell is constructed with representative volume elements of α2 and γ-phases (matrix and twin γ-phases with their orientation relationships). The constitutive behavior of the phases is described by a continuum mechanics based crystal plasticity model. The unit cells (at micro-scale) are used as a material sub-model for the polycrystal (at macro-scale). The description of the microstructure is obtained through the quantitative analysis of microstructure with SEM investigation of a particular TNB alloy. Two different duplex type microstructure is modeled. The material parameters of the α2 and γ-phases are initially taken from the literature and modified to fit the behavior of the niobium-containing TiAl alloy, correlating the experimental tensile records at room temperature with the simulation results. The model provides an insight into the local variation of stresses and strains of the duplex microstructure The role of dislocations and slip systems on the evolution of local plastic deformation will be discussed.