Einfluß eines Verformungsgradienten auf das Rekristallisationsverhalten von Titan Grad 2 / The Effect of Deformation Gradients on the Recrystallisation Behaviour of Titanium Grade 2

Abstract

The recrystallisation behaviour of cold drawn Titanium Grade 2 was investigated at various different annealing times and temperatures. Because of the deformation gradient inherent in the material, recrystallisation does not take place simultaneously throughout the material, but instead in layers from the outside towards the centre of the material. In the temperature range 700 to 800 °C, recrystallisation is accelerated and the critical degree of deformation necessary for recrystallisation to take place decreased by an increase in temperature. In contrast however, at temperatures above 800 °C up to the β-transition temperature of about 890 °C, recrystallisation is retarded by increasing the temperature and the critical degree of deformation increases by the recovery processes taking place. The grain size resulting from recrystallisation is in the main determined by the local degree of deformation of the material. As a result of this a grain size gradient is formed with coarser grains forming increasingly towards the centre of the material. Both the annealing temperature and time determine the depth of the recrystallised zone, and thus the maximum size of the grains.