Recrystallization behavior during hot tensile deformation of TA15 titanium alloy sheet with substantial prior deformed substructures

Dynamic recrystallization to a large extent determines the microstructure of near-α titanium alloys during the thermo-mechanical processing in α + β two phases zone. And the initial microstructure has a dramatic effect on the recrystallization behavior. Therefore, this paper deals with the recrystallization behavior of a near-α TA15 titanium alloy sheet with substantial prior deformed substructures during the annealing and hot tension at 800 °C. Undeformed and deformed regions of tensile samples, viz., static recrystallization and dynamic recrystallization, were studied respectively through EBSD observation. It was found that, the unusual intragranular nucleation of discontinuous recrystallization was observed in the relatively coarse grains, which was formed by the enclosed low angle grain boundaries rearranged by the thermally activated recovery. And most of the recrystallized grains manifested as three types of special grain boundaries, namely [0001]30 ^° , 112¯075 ^° and 138¯5¯390 ^° , which showed the cusps in grain boundary energy and can stabilize the recrystallized grain embryo. The substantial prior deformed substructures of the employed TA15 sheet, viz., low angle grain boundaries and dislocations, can facilitate the formation of subgrains and nucleation, which brought about a mixture of continuous and discontinuous recrystallization, regardless of dynamic or static. During the hot tension, the activation of dislocations would accelerate the annihilation and rearrangement of dislocations, thus, recrystallization can take place more frequently, which finally leads to an equiaxed microstructure.