“…Ultrasonic properties, which result from the interactions between the ultrasonic wave and the microstructures of materials, have been extensively used for optimizing heat treatment processes [ 12 , 13 ] and characterizing the microstructures [ 14 , 15 ] and mechanical properties [ 16 , 17 ] of materials. Ultrasonic velocity and attenuation reflect variations in the grain size [ 18 , 19 ], volume fraction, the size of the precipitated phase [ 20 , 21 , 22 , 23 ], the type of precipitated phase [ 15 , 24 ], and the defects during the heat treatment of superalloys. Ultrasonic velocity has been reported to increase with the formation of the precipitate phases, whereas the dissolving or coarsening of precipitates leads to decreases in velocity [ 12 , 14 , 15 , 16 , 20 , 21 , 22 , 25 ].…”