Relationship between near-surface ultrasonic shear-wave backscatter and grain size in metals
Backscattered ultrasonic microstructural noise can be used to estimate grain size in metals. However for normal-incidence immersion measurements the ring-down of the front-wall echo creates a ”dead zone” where backscattered grain noise cannot be quantified. This poses a problem for near-surface grain sizing efforts. In this paper we explore the use of mode-converted 45-degree shear waves for near-surface grain sizing using a water immersion setup. We discuss how to accurately relate grain noise arrival time with depth of sound penetration in the metal. Then for a set of Ni-alloy specimens having near-equiaxed microstructures we correlate various backscattered noise attributes with grain sizes determined from micrographs. These noise attributes include both time-domain and frequency-domain characteristics. The backscattered grain noise attributes correlate well with grain size, and are relatively insensitive to modest changes in the transducer tilt angle.
This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Engle, Brady J., Frank J. Margetan, and Leonard J. Bond. "Relationship between near-surface ultrasonic shear-wave backscatter and grain size in metals." In AIP Conference Proceedings 1706, no. 1 (2016): 130004. DOI: 10.1063/1.4940607. Posted with permission.