Impact behavior and fracture mechanism of ductile cast iron with minor nickel addition at low temperature

Utilizing laser confocal microscopy, SEM, instrumented impact and other experimental methods, the influence of nickel content(0.0%-0.9%, mass fraction, the same below) on the microstructure and low temperature impact toughness of ductile cast iron(DCI) was investigated. The fracture mechanism of DCIs was studied further at different temperatures by using scanning electronic microscopy (SEM). The results show that ductile-to-brittle transition temperature of as-annealed DCIs with 0.7% Ni content is lower than -60 degree C, the impact energy of Charpy-type test is still higher than 12J at -70 degree C. Minor Ni addition of proper quantities might favor the grain refinement and matrix strengthen, low temperature impact toughness properties of DCIs are markedly improved.