In-grain and grain-to-grain textural inhomogeneities in coarse-grained tantalum

The recrystallization behavior of coarse-grained tantalum deformed at large strains is strongly dependent on its deformation microstructure. In this regard, a longitudinal section of a high-purity coarse-grained tantalum ingot obtained by double electron beam melting (EBM) was rolled at room temperature to thickness reductions varying from 70 to 92% followed by annealing in vacuum at 900 and 1200 C for 1 h. Microstructural characterization was performed in cold-rolled and annealed specimens using scanning electron microscopy (SEM) in the backscattered mode (BSE), electron backscattered diffraction (EBSD), and microhardness testing. Results show that recrystallization of individual grains is strongly dependent on the initial orientation. In consequence, recrystallization kinetics varies noticeably from one grain to another. Inhomogeneous in-grain and grain-to-grain spatial distributions of textures are found in the tantalum plates. Texture components belonging to the so-called γ fiber ({111}// ND) are in majority in the rolling plane. The presence of tiny recovered regions in the annealed plate is associated to stable orientations like rotated cube {001}<110>, which are very resistant to recrystallization even at high annealing temperatures. EBSD results also confirm the occurrence of growth selection during recrystallization in coarsegrained tantalum. (orig.)