The orientation dependence of hot deformation behaviors of Mo with elongated grains

• The transverse elongation at room temperature of Mo bars was highly improved.
• After upsetting, the microtexture evolves from <110> to <100> + <111>.
• <100> oriented grains deform homogeneously and cells are formed.
• <111> oriented grains deform non-homogeneously and microbands are formed.

Draw-forged pure molybdenum bars were hot upset along the longitudinal direction by different reduction. The evolution of microstructure was investigated by electron backscatter diffraction (EBSD). The results show that the transverse elongation of pure Mo bars increases gradually with the reduction of upsetting. The maximum value of transverse elongation is 5% as the reduction of upsetting reaches 80%. During the upsetting deformation process, the <110> fiber texture evolves into <100> and <111> fiber textures. Grains with <100> orientation are deformed homogeneously and dislocation cells are formed, while grains with <111> orientation are deformed non-homogeneously and microbands, especially microshear bands, are formed. The banded structure plays an important role on the rotation and elongation of grains with <111> orientation, and the formation of <111> fibers. A model is proposed to explain this process.