<p>In this study, the solidification behavior of EN-GJS-400-15 ductile cast iron inoculated with bismuth-bearing systems containing Bi, La, Al, Sb, and Zr-Mn was investigated using adaptive thermal analysis. Cooling curves obtained during solidification were evaluated in terms of eutectic solidification time, eutectic interval, cooling rate, and temperature differences associated with the eutectic reaction. The graphite morphology developed after solidification was characterized by graphite nodule count, average nodule diameter, and nodularity. The results revealed that (i) variations in adaptive thermal analysis parameters were directly associated with differences in graphite characteristics and matrix phase distribution, (ii) the Bi + Bi inoculation system produced a higher cooling rate and a narrower eutectic interval, resulting in a high graphite nodule count, high nodularity, and a predominantly ferritic matrix, (iii) the Bi + La system exhibited a longer eutectic solidification time and a wider eutectic interval, leading to a lower nodule count, larger average nodule diameter, and reduced nodularity, and (iv) the Bi + Zr-Mn system showed a larger temperature difference between the liquidus temperature and the minimum eutectic temperature, while maintaining an intermediate cooling rate and a higher pearlite fraction. These findings demonstrate that adaptive thermal analysis enables the differentiation of inoculant-dependent solidification behavior and provides a consistent basis for correlating thermal parameters with graphite morphology and matrix constitution in ductile cast irons.</p>