Ultrasonic velocity measurement to assess casting quality

The quality of a cast product depends on its macro- and microstructures and the type and amount of defects present in it. Grain size and porosity are two important features that determine the casting quality. Various methods have been used to determine the grain size and the porosity content of a casting. For example, measurement of ultrasonic parameters, viz attenuation and velocity are used to evaluate the casting quality non-destructively. In this paper, the influence of porosity, pore diameter and grain size on ultrasonic longitudinal wave velocity in Al-4.5% Cit alloy castings is presented. Cross-correlation method has been employed in this study to determine the ultrasonic velocity. The ultrasonic velocity has been found to vary marginally with an increase in the grain size which is attributed to the anisotropy in thin test specimens. The velocity also decreases when the porosity content of the casting increases. The pore diameter appears to have no influence on ultrasonic velocity at a given level of percentage porosity for the levels of porosities investigated in this study.