Dependence of Macro- and Micro-Properties on α Plates in Ti-6Al-2Zr-1Mo-1V Alloy with Tri-Modal Microstructure

摘要

Tri-modal microstructure is often the target microstructure of titanium alloy components. In this study, the parameters, such as volume fraction, size of primary equiaxed α (αp), secondary lamellar α (αs) and thin α plates (αt) in tri-modal microstructure of Ti-6Al-2Zr-1Mo-1V alloy are adjusted by double heat treatment procedures. The properties of these constituent phases and their effect on the macro-properties are then investigated. The results show that the hardness of primary α (αp) varies slightly with heat treatment routes. The hardness of α plates region including αs and αt increases with increasing αt volume fraction and not with decreasing thickness of αs and αt. Using volume average of the thickness of αs and αt as effective thickness (teff), the hardness of α plates region and teff follow the Hall-Petch relationship. Meanwhile, as αt volume fraction increases, colony structure of αs is gradually destroyed, which makes each αs have large deformation degree by multiple directions slip. When volume fraction ratio of αp, αs and αt is about 1:1:1, αp and αs can undergo relatively large deformation and αt can contribute relatively large strength to the alloy and therefore the alloy has both good strength and ductility.