Three-dimensional finite element analysis of unintended deformation of polycrystalline billet in micro-extrusion

An unintended anisotropic deformation of a polycrystalline billet has been observed in micro-extrusion, which implies that the extruded billet shows a curved shape rather than an intended straight curve. Although the deformation is considered to originate from the anisotropy of crystal grains, three-dimensional computational analyses are yet to be conducted owing to computational challenges. In this study, the anisotropic deformation behavior of a polycrystalline billet during micro-extrusion was investigated by performing three-dimensional finite element analyses based on the anisotropic elastoplastic constitutive model of a single crystal and its robust algorithm. To explain the effect of grain size on the unintended deformation of billet in micro-extrusion, several simulations for two extrusion dies were performed considering polycrystalline billets containing crystal grains between 100 and 20,000 in number, and the results were statistically analyzed. Anisotropic deformation appeared in the billets with fewer grains, owing to the anisotropy of the single crystal. The grain size, normalized with respect to the billet diameter at which the anisotropic deformation began to appear, was quantitatively estimated. These results are in agreement with the corresponding experiments. Furthermore, simulation results indicated that the extruded crystallographic texture decreased the anisotropic deformation in the case of large grains.

Automated summary

The anisotropic deformation behavior of a polycrystalline billet during micro-extrusion was investigated using three-dimensional finite element analyses. The study found that the deformation is influenced by the anisotropy of crystal grains and the grain size. The crystallographic texture of the extruded billet also plays a role in reducing anisotropic deformation, especially in the case of large grains.