Measurement of grain size in metals by acoustic scattering provides improved quality

The principle of the measurement technique is the scattering of ultrasound by discontinuities in the metal. Ultrasound in metals is dissipated by internal friction and scattered by discontinuities in the metallic structure. The grains or crystals of certain alloys are elastically anisotropic and have discontinuities at the grain boundaries which scatter ultrasound. It has been found through experimental work that ultrasound scattered from certain alloys is a function of mean grain size. As a result of this work a data base of ultrasonic back scatter against measured grain size was generated for a range of strip thicknesses and alloys