In situ monitoring of phase transformation kinetics under rapid heating of Ti–6Al–4V titanium alloy
Andi Idhil Ismail, Moukrane Dehmas, Elisabeth Aeby‐Gautier, Benoît Appolaire
Abstract
The phase transformation kinetics of Ti–6Al–4V alloy was studied during rapid heating using in-situ high energy synchrotron diffraction and in-situ electrical resistivity measurement for heating rates varying from 0.03 to 200 °C.s−1. The application of Rietveld refinement to high energy synchrotron data tracked the mass fraction, mean lattice parameters and Full Width at Half Maximum (FWHM). For increasing heating rates, results evidenced a shift in the dissolution of α to β phase temperature range from 600 °C for 0.25C.s−1 to 960 °C for 200 °C.s−1. A Continuous Heating Transformation diagram (CHT) was constructed demonstrating the effect of high heating rate. The result also demonstrated a much narrower temperature transformation range at high temperature. FWHM showed a time-dependent decrease of the stress level and/or chemical heterogeneity in the β phase before the start of the α phase dissolution. The mean lattice parameter evolution of β phase suggested that the α phase dissolution kinetics was diffusion controlled despite a heating rate reached of 200 °C.s−1, leading to chemical heterogeneities in the β phase.