The Influence of the Back Stress (X) and the Hardening Rate (dX/Xε_pqe) on Void Nucleation in α/β Titanium Alloys

Abstract
The study of void nucleation in four α/β titanium alloys has provided nucleation criteria corresponding to voids at the α/β interface. This macroscopic nucleation criterion, written as ∑m=f(ε_pqe), was explained with the help of microscopic observations. Microscopic parameters such as plastic strain in the α-phase or local hydrostatic stress σm at the α/β interface have been linked to the damage initiation. Besides, the influence of the different heterogeneity levels on the macroscopic nucleation criterion was demonstrated using the macroscopic mechanical parameters : back stress (X) and hardening rate (dX/Xε_pqe) which express the plastic strain incompatibilities and their evolution in such alloys.