Predicting the effects of microstructural features on strain localization of a two-phase titanium alloy

Strain localization influenced by microstructural features has an important effect on mechanical properties of alpha + beta titanium alloy. To address the effect, a microstructure-based finite element model is established. In this model, regions for primary alpha (alpha(p)) and transformed beta matrix (beta(t)) are generated from real microstructures of a two-phase titanium alloy (TA15 alloy); the plastic flow behaviors of these two features are determined directly rather than from single phase alloy. A constitutive equation of alpha(p) is developed with consideration of dislocation-obstacle interaction, whereas the constitutive equation of beta(t) is determined by nanoindentation tests. Finally, the calculated stress-strain responses of the alloy are verified by experiments. The simulated results show that strain localization bands (SLBs) have two morphologies: short and long-continuous SLBs. Lots of short SLBs appear mainly in beta(t) and alpha(p) when the volume fraction of alpha(p) is small and moderate, respectively. Long-continuous SLBs appear mainly in alpha(p) when the volume fraction of alpha(p) is large. With the increase of alpha p in SLBs, the strength of the alloy decreases while the ductility increases. By decreasing the disparity of strength between alpha(p) and beta(t), the strain gradient in SLBs reduces and the ductility of the alloy increases. (C) 2015 Elsevier Ltd. All rights reserved.