Effect of Crystallographic Orientation on the Formation of α-Case in Ti-6Al-4V Titanium Alloy

The α-casing is a well-known phenomenon during the heat treatment of Ti-6Al-4V alloys. This work investigates the role of crystallographic orientation on α-case thickness. Specimens were heat-treated below the β-transus temperature followed by air cooling in a vacuum and air medium. The microstructural analysis revealed that the crystallographic orientation significantly influences the α-case thickness. {0001} Plane resists the oxygen diffusion and results in a relatively thin α-case formation which is also confirmed by microhardness variation.