James Coakley

Isothermal omega formation and evolution in the Beta-Ti alloy Ti-5Al-5Mo-5V-3Cr

Abstract The isothermal phase of Ti-5Al-5Mo-5V-3Cr wt.% is formed within a heat treatment at and identified by atom probe tomography as Ti-rich/solute lean precipitates. The composition and size remain essentially constant during ageing, although the volume fraction increases to 9.5% after ageing for 8 h. This is consistent with an ongoing transformation process of athermal to isothermal . The / interface becomes enriched with oxygen. This may be of significance as oxygen strongly stabilizes the phase, and the / interface has previously been suggested as the nucleation site for subsequent formation.

Isothermal omega kinetics in beta-titanium alloys

Abstract Small angle X-ray and neutron scattering provide a non-localised quantitative analysis of nanoscale precipitates in Ti-7Mo at.% and Gum metal, a Ti-Nb based alloy. The nucleation and coarsening kinetics are more rapid in the Ti-Nb alloy than the Ti-Mo alloy, presumably as Nb diffuses more rapidly than Mo in Ti. Therefore Mo-based -Ti alloys are more stable during ageing than Nb-based -Ti alloys. To the authors’ knowledge, this represents the first publication quantifying size, volume fraction and element partitioning in Gum metal.

Atom-Probe Tomography: Detection Efficiency and Resolution of Nanometer-Scale Precipitates in a Ti-5553 Alloy

1 Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA 2 Center for Atom-Probe Tomography (NUCAPT), Northwestern University, Evanston, IL, USA 3 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, England 4 Department of Materials, Imperial College, South Kensington, London, England 5 Rolls Royce Plc, Elton Road, Derby, England 6 CAMECA Instruments, Inc., Madison, WI, USA 7 Department of Materials, University of Oxford, Oxford, England