In situ characterizations of phase transformations kinetics in the Ti17 titanium alloy by electrical resistivity and high temperature synchrotron X-ray diffraction

The β ( BCC ) → α ( HCP ) + β ( BCC ) phase transformation kinetics of the β -metastable titanium alloy Ti17 was studied by in situ high energy X-ray diffraction (XRD) and electrical resistivity. The use of synchrotron radiation ( E = 89.12  keV, λ = 0.01402  nm) allowed to characterize specimens 6 mm in diameter, limiting thus oxidation effects. The α + β → β phase transformation kinetics was characterized during continuous heating up to the β temperature range. The β → α + β transformation was studied in isothermal conditions (dwell at 708  ° C or 750  ° C) and during continuous cooling (cooling rates of 0.05  ° C/s, 0.1  ° C/s and 0.61  ° C/s). The evolutions of the phase fractions are analyzed and compared to kinetics measured by electrical resistivity, showing a good correlation between both methods. In addition, the evolutions of the cell parameters of each phase obtained from XRD patterns are analyzed in regard of the transformation kinetics.