Plasticity of initially textured hexagonal polycrystals at high homologous temperatures: application to titanium Original Research Article

A crystal-plasticity-based constitutive model for the large deformation of polycrystalline materials with hexagonal crystal structure deforming by crystallographic slip at high homologous temperatures has been developed. The constitutive model has been implemented in a finite-element program. In our finite-element model of a polycrystal, each element represents one crystal, and a set of crystal orientations which approximate the initial crystallographic texture of the hexagonal material are assigned to the elements. The macroscopic stress–strain responses are calculated as volume averages over the entire aggregate. Nominally homogeneous experiments in simple tension, simple compression, plane-strain compression and thin-walled tubular torsion have been conducted on initially textured commercially pure titanium at 750°C, and the resulting macroscopic stress–strain response and evolution in crystallographic texture have been measured. Numerical experiments were conducted, and matched to the data from the simple tension and compression experiments to determine the operative slip systems and the material parameters in the constitutive model. Using this information, the predictions of the stress–strain response and texture evolution for plane-strain compression and thin-walled tubular torsion are shown to be in good agreement with the corresponding experimental measurements.