Ultrasonic non-destructive evaluation of the matrix structure and the graphite shape in cast iron

The purpose of this investigation was to determine the ultrasonic characteristics (velocity and attenuation) of cast irons with different nodularities and matrix structures, and to correlate these with their mechanical properties. The results indicated that there was a definite relationship between the degree of nodularity of graphite and the ultrasonic velocity, but the influences of matrix structure on the ultrasonic velocity was not clear. The attenuation of the ultrasonic amplitude increased with decreasing nodularity. Ferritic, pearlitic, tempered martensitic and bainitic matrix structures were found to have similar attenuation characteristics, but greater amounts of tempered martensite or pearlite resulted in greater attenuation.