Ultrasonic flaw detection for two-phase Ti-6Al-4V based on secondary scattering

Ultrasonic inspection of two-phase Ti-6Al-4V materials is enhanced using a more complex microstructure model within the doubly-scattered response (DSR) limit. The new model is used to calculate the corresponding bounds of grain noise and these bounds are then used to define a time-dependent threshold for ultrasonic testing. A Ti -6Al-4V specimen with flat bottom holes is manufactured for ultrasonic measurements to verify the measurement sensitivity to sub-wavelength flaws. The experimental results show that the present method has obvious advantages over traditional methods associated with a fixed threshold as well as the time-dependent threshold based on the singly-scattered response (SSR). This work provides an effective tool for distinguishing sub-wavelength flaws from grain noise, thereby limiting both false positives and missed detections.