In situ monitoring of phase transformation kinetics under rapid heating of Ti-6Al-4V titanium alloy

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 degrees 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 a to beta phase temperature range from 600 degrees C for 0.25C.s(-1) to 960 degrees C for 200 degrees 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 beta phase before the start of the a phase dissolution. The mean lattice parameter evolution of beta phase suggested that the a phase dissolution kinetics was diffusion controlled despite a heating rate reached of 200 degrees C.s(-1), leading to chemical heterogeneities in the beta phase. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

The phase transformation kinetics of Ti-6Al-4V alloy were investigated during rapid heating, and the study showed that the heating rate had an influence on the phase transformation behavior. Higher heating rates resulted in a higher dissolution temperature range for the α phase and a narrower temperature range for the phase transformation. The stress level and/or chemical heterogeneity in the β phase decreased with time at high temperatures. Despite the high heating rate, the dissolution kinetics of the α phase were still diffusion-controlled.