PNNL

Abstract

Since its discovery in 1954, the omega (?) phase in titanium and its alloys has attracted substantial attention from researchers. The ß-to-? and ?-to-a phase transformations are central to ß-titanium alloy design, but the transformation mechanisms have been a subject of debate. With new generations of aberration-corrected transmission electron microscopy and atom probe tomography, both the spatial resolution and compositional sensitivity of phase transformation analysis have been rapidly improving. This review provides a detailed assessment of the new understanding gained and related debates in this field enabled by advanced characterization methods. Specifically, new insights into the possibility of a coupled diffusional-displacive component in the ß-to-? transformation and key nucleation driving forces for the ?-assisted a phase formation are discussed. Additionally, the influence of ? phase on the mechanical properties of ß-titanium alloys is also reviewed. Finally, a perspective on open questions and future direction for research is discussed.