Recent Developments in Heat Treatment of Beta Titanium Alloys for Aerospace Applications

A Review of Metastable Beta Titanium Alloys

“…In this state, an alloy has low strength but high ductility. Solution treatment in the single β-phase field for too long can, however, result in excessive grain growth and coarsening of the bcc β-phase that negatively affects mechanical properties [104,124]. Alpha-beta solution treatment leads to enrichment of the bcc β-phase according to the lever rule for equilibrium phase diagrams.…”

“…In this state, an alloy usually has comparatively higher strength but lower ductility. In general, the size, morphology, and volume fraction of the primary α-phase influence the mechanical properties, providing an important route to optimize the mechanical behavior of beta Ti alloys [124]. The metastable Beta C alloys, which has an MoE value of 16.0, is an example of an alloy that is solution treated at super-transus temperatures.…”

“…Modifications of the aforementioned four methods have also been presented in the literature [128]. [124]. Secondary hcp α-phase precipitates, which is an equilibrium phase, form initially at the bcc β-phase and then intragranularly at longer aging times.…”

“…These studies typically focus on microstructural evolution of the secondary α-phase precipitates and concomitant changes in tensile or hardness properties. Low-temperature aging is typically conducted at approximately between 200 °C (392 °F) and 450 °C (842 °F) [34,124]. In this temperature range intermediate metastable phases such as the isothermal ω-phase or the β′-phase may form before the equilibrium hcp α-phase.…”

“…Studies are present in the existing literature on microstructural evolution of the secondary α-phase precipitates and concomitant changes in tensile or hardness properties during low temperature aging [69,131]. However, recent interest on the nucleation and growth mechanisms of the secondary α- [34,124]. In this temperature range intermediate metastable phases such as the isothermal ω-phase or the β -phase may form before the equilibrium hcp α-phase.…”