2020/10/26 by Felicity F. Dear, Dear, Felicity F., Paraskevas Kontis +9
Engineering · #Advanced Materials Characterization Techniques #FOS: Physical sciences #High Temperature Alloys and Creep #Intermetallics and Advanced Alloy Properties #Materials Science (cond-mat.mtrl-sci)
paper · pdf · doi:10.48550/arxiv.2010.13894
openalex publication_date 2020/10/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Nucleation and growth of Ti3Al \textalpha2 ordered domains in \textalpha-Ti--Al--X alloys were characterised using a combination of transmission electron microscopy, atom probe tomography and small angle X-ray scattering. Model alloys based on Ti--7Al~(wt.%) and containing O, V and Mo were aged at \SI550\celsius for times up to \SI120\day and the resulting precipitate dispersions were observed at intermediate points. Precipitates grew to around \SI30\nano\metre in size, with a volume fraction of 6--10% depending on tertiary solutes. Interstitial O was found to increase the equilibrium volume fraction of \textalpha2, while V and Mo showed relatively little influence. Addition of any of the solutes in this study, but most prominently Mo, was found to increase nucleation density and decrease precipitate size and possibly coarsening rate. Coarsening can be described by the Lifshitz-Slyozov-Wagner model, suggesting a matrix diffusion-controlled coarsening mechanism (rather than control by interfacial coherency). Solutionising temperature was found to affect nucleation number density with an activation energy of Ef = 1.5±0.4~eV, supporting the hypothesis that vacancy concentration affects \textalpha2 nucleation. The observation that all solutes increase nucleation number density is also consistent with a vacancy-controlled nucleation mechanism.