Microstructure and Low-Temperature Impact Behavior of ADI Containing Ni

The effects of Ni content on the microstructure and low-temperature impact fracture behavior of ADI were systematically investigated by SEM, XRD, TEM, and the Charpy V-notch impact test method. The results demonstrate the average size of graphite nodules decreases with the increase in Ni content. The nodularity of all samples is above 80%, showing a trend of increasing first and then decreasing. Additionally, the volume fraction of the austenite phase in ADI increases with the addition of Ni. The increase in Ni content improves the tensile strength and elongation of ADI simultaneously. The values of tensile strength and elongation reach the maximum of 1007 MPa and 9.2%, respectively, when the Ni content is 0.7 wt%, which are 9.46% and 13.58% higher than the ADI without Ni content. In addition, the addition of Ni will reduce the dislocation density in ADI, resulting in a significant improvement of the low-temperature impact toughness. The impact energy of ADI with 0.7 wt% Ni addition is 6.1 J at − 40 °C.