1. Dynamic and static microstructural changes

1.1 A reminder of titanium alloy metallurgy

Ultra-pure titanium has a pseudo-compact hexagonal structure known as the α phase up to 882°C. Above this temperature, known as β-transus (T _β ), the crystallographic structure becomes cubic-centered and is termed β-phase. The effects of addition elements are, to a first approximation, additive, and they increase or lower the transus value.

The alloys obtained are assigned to the following classes, according to the nature of the phases present at ambient temperature in the state of use:

• α class: alloys are made up of 100% α phase;

• α + β class: alloys with highly variable proportions of α and...