The annealing behavior of oligocrystalline tantalum deformed by cold swaging

The annealing behavior of coarse-grained tantalum deformed at large strains (ε>1) is strongly dependent on deformation microstructure. In this regard, a high-purity coarse-grained double electron-beam melted tantalum ingot was deformed to a true strain of 6.4 by cold swaging and annealed between 400 and 1100°C. The annealing behavior was investigated in specimens deformed at three true strains: 1.3, 2.8 and 5.0 using light optical microscopy, scanning electron microscopy in the backscattered mode and microhardness testing. Results show that recrystallization kinetics varies noticeably from grain to grain. Even after annealing at 1100°C for 1 h, the microstructure of tantalum deformed to a true strain of 5.0 predominantly consists of alternating bands of recrystallized grains with distinct size distributions and a few elongated areas softened by recovery indicating pronounced orientation effects.