ANALYTICAL DESCRIPTIONS OF DYNAMIC SOFTENING MECHANISMS FOR Ti-13Nb-13Zr BIOMEDICAL ALLOY IN SINGLE PHASE AND TWO PHASE REGIONS

Dynamic softening behaviors of a promising biomedical Ti-13Nb-13Zr alloy under hot deformation conditions across dual phase alpha + beta and single phase beta regions were quantitatively characterized by establishing corresponding dynamic recovery (DRV) and dynamic recrystallization (DRX) kinetic models. A series of wide range hot compression tests on a Gleeble-3500 thermo-mechanical physical simulator were implemented under the strain rate range of 0.01-10 s(-1) and the temperature range of 923-1173 K. The apparent differences of flow stress curves obtained in dual phase alpha + beta and single phase beta regions were analyzed in term of different dependence of flow stress to temperature and strain rate and different microstructural evolutions. Two typical softening mechanisms about DRV and DRX were identified through the variations of a series of stress-strain curves acquired from these compression tests. DRX is the dominant softening mechanism in dual phase alpha + beta range, while DRV is the main softening mechanism in single phase beta range. The DRV kinetic model for single phase beta region and the DRX kinetic model for dual phase alpha + beta region were established respectively. In addition, the microstructures of the compressed specimens were observed validating the softening mechanisms accordingly.