Grain Size, Texture, and Materials Variation Measurements using Scanning Acoustic Microscopy (SAM) and Ultrasonic Backscatter, Diffuse Field, and Birefringence Measurements

National Laboratory: 
Pacific Northwest National Laboratory
Characterization Class: 
Microscopy
Non-destructive examination
Description: 

Grain size, texture, and material variation measurements can be performed using complementary ultrasonic techniques that include: 

  • Scanning acoustic microscopy (SAM). This method uses a transducer with an ultrasonic frequency that typically is 20 MHz or higher to resolve micro-features and produce high-resolution images of surface and sub-surface material features.
  • Ultrasonic backscatter and diffuse field measurements. These measurements are performed at ultrasonic frequencies whose wavelengths in the material under test are comparable to microstructure length scales, allowing for grain size characterization.
  • Ultrasonic birefringence measurements. This method uses linearly polarized shear waves to determine the principal directions of elastic anisotropy caused by texture or residual stress to characterize the degree of texture or stress state in bulk components.
Capability Bounds: 

Measurements require direct contact between the transducers and the material or a liquid couplant, such as water, to facilitate standoff measurements.

Unique Aspects: 

PNNL has a scanning acoustic microscope capable of ultra-high resolution (0.5 micron) three-dimensional imaging of surface and sub-surface micro-features, along with the necessary ultrasonic equipment for performing ultrasonic backscatter, diffuse field, and birefringence measurements.

Availability: 

No availability limits.

Single Point of Contact: 

Name: Darrell Herling
Email: darrell.herling@pnnl.gov
Phone: 509-375-6912

References: 
  1. Ramuhalli, P., Good, M., Harris, R., Bond, L., Ruud, C., Diaz, A., Anderson, M., 'Methods for the In-situ Characterization of Cast Austenitic Stainless Steel Microstructures,' Proceedings of the 37th Annual Review of Progress in Quantitative Nondestructive Evaluation 2010, San Diego, California.
  2. Doctor, S., Bruemmer, S., Good, M., Charlot, L., Taylor, T., Boyd, D., Deffenbaugh, J., Reid, L., 'Utilization of Ultrasonic Measurements to Quantify Aging-Induced Material Microstructure and Property Changes,' Symposium at the 1988 Fall Meeting Of The Materials Research Society: Nondestructive Monitoring of Materials Properties, Boston, Massachusetts.