Precipitation of β' Phase in a Low Cost Beta Titanium Alloy
Precipitation behavior of a metastable β Ti alloy, Ti-6.8Mo-4.5Fe-1.5Al(masss%), during two-step aging has been investigated. Supersaturated β phase after solution treatment decomposes into β+ω phases during the first aging at 300°C for 2ks. β′ phase is observed during the second aging at 500°C for 50s. It is suggested that reverse transformation of the ω phase to β phase during the second aging at 500°C for 50s gives rise to solute-lean and –rich regions in the β phase, and that β′ phase is formed in the solute-rich region. β′ phase being coherent with β phase has larger lattice parameter than β phase. β′ phase acts as nucleation site for α phase, and accelerates the nucleation of α phase.
T. Chandra, N. Wanderka, W. Reimers , M. Ionescu
T. Sakamoto et al., "Precipitation of β' Phase in a Low Cost Beta Titanium Alloy", Materials Science Forum, Vols. 638-642, pp. 461-464, 2010