Oxygen-Induced Refinement Of Alpha Precipitates In An Aged Metastable Beta Ti-15-333 Alloy

Increasing the strength of aged metastable beta titanium alloys through refinement of intragranular alpha precipitates has been previously demonstrated using heterogeneous nucleation on structural and compositional non-uniformities. Here, we show that elevated oxygen levels (up to 1.7 at. %) can also induce alpha phase refinement during ageing of a beta Ti-15-333 alloy, providing an additional pathway to obtain fine alpha laths. Moreover, oxygen-induced refinement combined with omega-assisted alpha nucleation resulted in significantly reduced alpha sizes of similar to 50 nm. The finer alpha precipitates obtained with higher oxygen concentrations resulted in increased compressive yield strengths during micropillar compression compared to specimens without oxygen. These findings highlight the use of high oxygen contents to improve alpha microstructural refinement and precipitation strengthening in beta Ti alloys. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.