Study on the effect of ultrasonic treatment for fabricating nodular cast iron with improved mechanical properties

In this paper, a novel ultrasonic treatment technique was proposed in nodular cast iron melt with the aim of improving the microstructure and mechanical properties of nodular cast iron. The effects of ultrasound on the microstructures and properties were investigated by comparing experiments with and without ultrasound. The results showed that compared with the NO UT specimen, the mean equivalent diameter of graphite nodules was reduced by 46% in the UT 105 s specimen, while the mean roundness and nodule count per unit area were increased by 33.9% and 43.6%, respectively. In addition, the ultrasonic treatment of melt could increase the pearlite content, refine the matrix microstructure and reduce the pearlite interlamellar spacing from 392.7 nm to 231.3 nm. Compared with the NO UT specimen, the mechanical properties of the UT specimen were improved significantly, and could up to UTS of 739 MPa, YS of 579 MPa and El of 9.4% in the UT 105 s specimen. In this work, the mechanism of ultrasonic action on nodular cast iron also was discussed in detail.