GRAIN-SIZE MEASUREMENTS IN AUSTENITIC STAINLESS-STEEL USING ULTRASONICS

Ultrasonic technique offers a non-destructive means to measure average grain size in materials. Conventional ultrasonic attenuation method involves the measurement of the attenuation coefficient from the changes in the peak heights of several backwall echoes. For a highly attenuating material such as austenitic stainless steel, particularly when the thickness is high, peak heights beyond the first backwall echo are often negligible, making it difficult to use the conventional ultrasonic attenuation method. In such cases, the peak height of the first backwall echo can alone be considered and correlated with the grain size of the material, if the thickness of the reference (used for calibration) and test material is the same. This paper gives the results of this approach for grain size determination in specimens of AISI type 316 austenitic stainless steel. The grain size data obtained by this approach are found to agree with those obtained by conventional metallography.