Ultrasonic TechniquesUltrasonic velocity is directly connected to the elastic moduli and the density of a solid material. By ANALYZING ultrasonic shear and longitudinal wave velocities, the Young?s MODULUS and shear modulus can be determined and by this the Poisson ratio. An excellent review on the evaluation of mechanical properties from ultrasonic attenuation and velocity MEASUREMENTS can be found in Vary (1986).The ultrasonic velocity and attenuation have been CORRELATED to hardness in various steels. In general, the velocity and attenuation coefficients are found to vary inversely with hardness in case-hardened, quenched, and tempered steels. In the case of 9Cr–1Mo ferritic steel, the ultrasonic longitudinal and shear wave velocities are used to determine the hardness of the steel with different amounts of ferrite and martensite. Ultrasonic velocity measurements are found to be useful for on-line assessment of the extent of degradation of mechanical properties associated with precipitation of intermetallics in Inconel 625. Different correlations are observed for ultrasonic velocity and yield strength upon precipitation of intermetallic phases with different coherency with the MATRIX