  The presence of macrozones (or micro-textured regions) in Ti-6Al-4V (Ti64)
was shown to be a potential cause to the onset of cold dwell fatigue which
reduces fatigue life significantly. Past research has demonstrated the
potential of using ultrasonic testing for macrozone characterisation, with the
variation of ultrasound attenuation, backscatter, and velocity in the presence
of macrozones. However, due to the complexity of the microstructure, some
physical phenomena that were observed are still not well understood. In this
study, we propose the use of Finite Element (FE) polycrystalline models to
provide us with a means to systematically study the wave-macrozone interaction.
Through this investigation performed using two-dimensional (2D) models, we are
able to identify important correlations between macrozone characteristics
(size, shape, and texture) and ultrasound responses (attenuation, backscatter,
and velocity). The observed behaviours are then validated experimentally, and
we also highlight how this understanding can potentially aid with the
characterisation of macrozones in Ti-64 samples.
