Kinetics of Recrystallization and Grain Growth in Ti-17 Alloy

The aim of this research is to simulate the forging step in the two phase alpha/beta-range followed by recrystallization in the beta field during which microstructure evolves. This involves the following phenomena: grain deformation, recrystallization and grain growth for the beta matrix and disorientation/fragmentation for the alpha Widmanstatten platelets. More specifically, this work analyzes the effects of a deformation in the alpha/beta field on the subsequent beta grain growth during a heat treatment at higher temperatures for a Ti-17 titanium alloy. The experimental part is based on uniaxial compression tests in order to simulate the forging step. The complete thermomechanical treatment starts with a temperature homogenization step (10min) followed by uniaxial compression with a strain rate of 10(-2) s(-1) in the alpha/beta-phase field and a water quenching; the samples are then subjected to a recrystallization / grain growth step at higher temperatures (in the beta-phase domain). The evolution of grain structures and substructures were investigated by optical and scanning electron microscopy (SEM) and electron backscattering diffraction (EBSD). The influence of strain and heat treatments time on the microstructure is described. The kinetics of recrystallization and grain growth in the alloy have been determined.