Abstract
Ti-Al alloys can suffer from a chemical decomposition on ageing around 500°C or on air cooling. At long ageing times this results in the formation of α2 (Ti3Al) precipitates. At reduced times or elevated temperatures, diffuse electron or neutron diffraction peaks can be observed, which has been termed 'short range ordering' (SRO). Here, we present correlative transmission electron microscopy (TEM) and atom probe tomography (APT) results showing that the reaction proceeds through the formation of ordered Al-rich precipitate clusters. Notably, Al-Al clustering could be observed well before the appearance of distinct precipitates in the TEM. In addition, the V-containing α phase of Ti-6Al-4V formed ordered clusters much faster than in binary Ti-7Al. This implies that the ternary addition of β stabilisers exacerbates the problem of α2 precipitate formation in commercial dual phase titanium alloys.
Original language | English |
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Pages (from-to) | 141-149 |
Number of pages | 9 |
Journal | Acta Materialia |
Volume | 112 |
Early online date | 18 Apr 2016 |
DOIs | |
Publication status | Published - 15 Jun 2016 |
Funding
This research was supported by a Rolls-Royce plc – EPSRC CASE studentship. Material for the study was provided by Timet. Helpful discussions with Prof. T.C Lindley, Prof. G.D.W. Smith, Prof. M.H. Loretto and Prof. I.P. Jones are gratefully acknowledged. Experimental assistance was generously provided by Prof. J.P. Bradley, Dr K.M. Rahman, Dr C. McGilvery, Dr M. Ardakani and Dr D. Isheim. VV and JC would like to acknowledge support from an EPSRC doctoral prize fellowship , EU Marie Curie fellowship respectively. DD was supported by EPSRC grants EP/K034332/1 and EP/H004882/1 .
Keywords
- atom probe tomography (APT)
- ordering
- titanium alloys
- transmission electron microscopy (TEM)