Abstract
Abstract Precipitate evolution in Ti-5Al-5Mo-5V-3Cr-0.3Fe wt.% (Ti-5553) has been studied in-situ by small angle neutron scattering (SANS) during a two step ageing heat treatment of 300°C/8h+500°C/2 h. The first heat treatment step precipitates ω, with a corresponding increase in hardness of ∼15% compared to quenched material. The second heat treatment step precipitates fine scale α from the ω phase, with a ∼90% increase in hardness compared to quenched material. The SANS measurements are complemented by atom probe tomography (APT) to give compositional information, ex-situ transmission electron microscopy (TEM) to confirm phase identification and size distribution locally, and X-ray diffraction (XRD) for additional confirmation of phase identification. The ω phase is depleted in all the solute additions following 300°C/8 h ageing heat treatment. The volume fraction of the ω phase from APT is estimated to be ∼7%. SANS modelling is consistent with disc shaped particles for the ω phase. The mean particle diameter increases from ∼7.5 nm to 9.5 nm diameter between 1 h and 8 h heat treatment at 300 °C, while the thickness increases from ∼4 nm to ∼5 nm. The SANS model estimates the volume fraction to be ∼10% for the 8 h heat treatment, using the phase compositions from APT.
Original language | English |
---|---|
Article number | 34520 |
Pages (from-to) | 946-953 |
Number of pages | 8 |
Journal | Journal of Alloys and Compounds |
Volume | 646 |
DOIs | |
State | Published - Jul 7 2015 |
Funding
The authors would like to acknowledge funding from EPSRC under grant EP/H0004882/01 . VAV and JC would like to acknowledge support from the EPSRC doctoral prize fellowship and Marie Curie fellowship respectively. This work utilizes the Oak Ridge National Laboratory's High Flux Isotope Reactor, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy . JC would like to thank R Chater for providing training in FIB milling and his helpful discussions. For the APT analysis, T.L. Martin is thanked for assistance with running samples and M.P. Moody for helpful discussions. PAJB acknowledges support from The Queen's College Oxford for experiments performed at Harvard University, USA.
Keywords
- Atom probe tomography (APT)
- Precipitation
- Small angle neutron scattering (SANS)
- Titanium alloys
- Transmission electron microscopy (TEM)