The role of the ω phase on the non-classical precipitation of the α phase in metastable β-titanium alloys

The metastable beta-Ti alloy, Ti-5553, has been heat-treated to permit a determination of the role of the omega phase on non-classical precipitation of the alpha phase. Thus, samples containing the athermal omega phase have been up-quenched to 600 degrees C. The observations made are consistent with the activation of the non-classical, pseudo-spinodal, nucleation mechanism, with the omega phase playing essentially no direct role. The alpha/beta interfacial structures have been shown to exhibit significant degrees of coherency compared with those in conventional alpha/beta alloys, and implications of this on lowering the interfacial energy, and so the activation for nucleation, are discussed. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.