| Isothermal forgings of mill-annealed, unidirectionally-rolled, and cross-rolled Ti-6Al-4V alloys were performed at temperatures of 830, 880 and 925℃ with the true strain rates of 1×10^(-3)/sec and 5×10^(-3)/sec. Flow stresses and microstructural evolution of the specimens during the forging were characterized. The flow behavior and microstructural changes during forging have been found to depend on initial microstructure of the specimens and forging conditions. Dynamic recrystallization and strain softening occurred in unidirectionally-rolled specimens, which had elongated α grains. On the other hand, mill-annealed and cross-rolled specimens, of which initial microstructure do not have elongated α grains, did not show distinct dynamic recrystallization under the same forging conditions. It was also shown that the Zener-Hollomon parameter is a good factor to characterize the steady-state stresses and the final grain size of the unidirectionally-rolled specimens during/after the forging under the given conditions. |
|
