Constitutive analysis of the high-temperature deformation of Ti-6Al-4V with a transformed microstructure

Abstract

The high-temperature deformation mechanisms of Ti-6Al-4V with a transformed microstructure were determined within the framework of inelastic-deformation theory. For this purpose, load-relaxation tests were conducted on samples with a lamellar structure containing different alpha-platelet thicknesses at temperatures of 715-900 degreesC. The flow stress-versus-strain rate curves for all the microstructures were well fit with an inelastic-deformation equation describing grain-matrix deformation (GMD) (dislocation glide + dislocation climb). However, for heavily pre-deformed specimens, grain-boundary sliding (GBS) as well as GMD was evident. The GBS rate was found to be most rapid for the microstructure with the thinnest alpha laths/platelets. Softening of heavily deformed material was attributed to a decrease in the internal-strength variable sigma* associated with reduced alpha-beta interface strength and to the occurrence of GBS. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.