Constitutive analysis of the high-temperature deformation mechanisms of Ti-6Al-4V and Ti-6.85Al-1.6V alloys

Abstract

The high-temperature deformation mechanisms of a near-alpha titanium alloy (Ti-6.85Al-1.6V) and an alpha + beta titanium alloy (Ti-6Al-4V) were deduced within the framework of inelastic-deformation theory. For this purpose, load-relaxation tests were conducted on the two alloys at temperatures ranging from 750 to 900 degrees C. The stress versus strain rate curves of both alloys were well fit with inelastic-deformation equations which consisted of grain-matrix deformation (GMD) and grain-boundary sliding (GBS). The constitutive analysis revealed that the grain-boundary sliding resistance is higher in the near-alpha alloy than in the two-phase alpha + beta alloy due to the difficulty in relaxing stress concentrations at the triple-junction regions in the near-alpha alloy. In addition, the internal-strength parameter (sigma*) of the near-alpha alloy was much higher than that for the alpha + beta alloy, thus implying that dislocation emission/slip transfer at alpha/alpha boundaries is more difficult than at alpha/beta boundaries. (c) 2004 Elsevier B.V. All rights reserved.