On the stability of ω phase in Ti-6-22-22S and Ti-6-4 alloys

The diffuse intensities associated with the presence of ω phases were observed in Ti-6Al-2Cr-2Mo-2Sn-2Zr-0.2Si and Ti-6Al-4V alloys. A decrease in cooling rate from the β phase field lead to an increased shift of diffuse ω scattering |Δ|. The shift of the diffuse ω scattering |Δ| was associated with the enrichment of β stabilized elements in the β phase. A linear relationship was determined between the shift |Δ| and the 〈Mo〉 equivalent, and between the shift |Δ| and total-free-electron-to-atom e/a ratio. The occurrence of the shift |Δ| and the stability of the ω phase are believed to be related to the chemical short range order in the β phase of the alloys.