Analysis of backscattered ultrasound amplitude of Ti–5.8Al–4Sn–3.5Zr–0.7Nb–0.5Mo–0.3Si samples in terms of their microstructures and local textures

The amplitudes of backscattered ultrasound were measured at 10 MHz on different samples of the near-α titanium alloy Ti–5.8Al–4Sn–3.5Zr–0.7Nb–0.5Mo–0.3Si. Orientation imaging maps (OIMs) of these samples were also determined by electron backscatter diffraction. The backscattered amplitude appears to be related to the microstructure, notably to the orientations, volume fractions and spatial distribution of specific zones. These zones, named macrozones, are formed with a majority of primary αp grains and secondary αs colonies having nearly a common crystallographic axis. To illustrate the role of the microstructure on wave propagation, the local elastic constants determining the velocities of the longitudinal ultrasonic waves were deduced from the OIMs. The analysis of the spatial distribution and variations of the elastic constants explains the observed variations in backscattered ultrasound amplitude.