Study of the hot deformation behaviour in Ti-5Al-5Mo-5V-3Cr-1Zr

Structural applications of near beta titanium alloys are gradually increasing in the aerospace industry because of their high specific mechanical properties and good corrosion resistance. Furthermore, a wide range of microstructures can be obtained by thermomechanical processes. This work determines by the use of EBSD technique the mechanism of restoration active in the near beta titanium alloy Ti-5Al-5Mo-5V-3Cr-1Zr for deformations in both alpha + beta and 13 field near to the beta transus temperature (T-beta =803 degrees C). Hot compression tests are carried out up to 0.7 true strain by means of a Gleeble (R) 1500 machine at strain rates of 0.01, 0.1 and 1s(-1). Dynamic recovery of beta phase and rotation of the alpha grains take place predominantly in the alpha + beta field. Further deformation produces continuous dynamic recrystallization of the beta phase influenced by the strain rate. Dynamic recovery is observed during deformation above the T-beta, where the misorientation is increasing towards the grain boundaries forming new small grains with a substructure at high strain rates and larger deformation. The stress exponent and the apparent activation energy for the sinh constitutive equations are determined and the microstructural features are correlated with the Zener-Hollomon parameter. (C) 2011 Elsevier B.V. All rights reserved.