Influence of plastic formation parameters on structural characteristics of thermoelectric material during hot extrusion

We used mathematical modeling to compare the stress and deformation in a Bi0.4Sb1.6Te3 solid solution base thermoelectric material for extrusion through different diameter dies. The results show that extrusion through a 20 mm diameter die produces a more inhomogeneous deformation compared with extrusion through a 30 mm diameter die. Extrusion through a die of a larger diameter produces a structure that is coarser but has a more homogeneous grain size distribution. The degree of preferential grain orientation is higher for extrusion through a larger diameter die. We found a change in the lattice parameter of the solid solution along the extruded rod, correlating with detect formation during extrusion. The concentration of vacancies is higher for extrusion through a smaller diameter die. This difference between the structures results from a more intense dynamic recrystallization for a smaller diameter die. Increasing the die diameter and lowering the extrusion temperature allow retaining the thermoelectric properties of the material due to a better texture.