Influence of cooling rate on the precipitation kinetics of nanoscale isothermal ?-phase in metastable ?-Ti alloy, Ti–5Al–5Mo–5V–3Cr

In metastable ?-Ti alloys, nanoscale isothermal ?-phase (?iso) precipitates are regarded as the nucleation sites for ? strengthening phase. Here we investigate precipitation kinetics of ?iso a function cooling rate (air and water quenching) after ?-solutionising. A combined in situ small-angle neutron scattering (SANS) electrical resistivity measurement approach was used during ageing Ti–5Al–5Mo–5V–3Cr wt% (Ti-5553) alloy at 300 °C 325 up to 8 h. The SANS modelling consistent with ellipsoid shaped particles precipitates, both air-cooled water-quenched samples. attained maximum size (equatorial diameter) ?21 nm ?17 2 h 4 samples respectively. Although showed delayed comparison sample, volume fraction became approximately same (?11%) average value activation energy from ?-phase matrix determined 122 kJ mol?1 data using modified Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. hardness increased time, quenching leading higher final than air cooling.