In-situ laser ultrasonic measurement of the hcp to bcc transformation in commercially pure titanium

Using a novel in-situ laser ultrasonic technique, the evolution of longitudinal velocity was used to measure the alpha-beta transformation during cyclic heating and cooling in commercially pure titanium. In order to quantify the transformation kinetics, it is shown that changes in texture can not be ignored. This is particularly important in the case of titanium where significant grain growth occurs in the beta-phase leading to the ultrasonic wave sampling a decreasing number of grains on each thermal treatment cycle. Electron backscatter diffraction measurements made postmortem in the region where the ultrasonic pulse traveled were used to obtain an estimate of such local texture and grain size changes. An analysis technique for including the anisotropy of wave velocity depending on local texture is presented and shown to give self consistent results for the transformation kinetics. (C) 2016 Elsevier Inc. All rights reserved.