Spheroidization and dynamic recrystallization mechanisms of Ti-55511 alloy with bimodal microstructures during hot compression in α plus β region

Spheroidization and dynamic recrystallization (DRX) mechanisms of a Ti-55511 alloy during hot compression in alpha+beta region is investigated. It is found that the spheroidization of lamellar alpha phases and DRX of beta phases, which are obviously influenced by deformation conditions, are the main softening mechanisms. The spheroidization fraction of lamellar alpha phases first increases with the raised temperature or strain rate. However, the spheroidization fraction of lamellar alpha phases begins to drop at about 700 degrees C as the strain rate is higher than 0.01 s(-1), and the maximum spheroidization fraction of lamellar alpha phase is about 2.3%. This phenomenon is attributed to the Implanting-Mechanism, which is induced by the common or close orientation relationships of the spheroidized and equiaxed alpha phases, as well as few dislocations between the spheroidized and equiaxed alpha phases. Contrarily, the lamellar alpha phases are obstructed from equiaxed alpha phases by a mass of dislocations. Additionally, the DRX degree of beta phases increases with the reduced temperature or the raised strain rate.