The role of microsegregation on eutectic morphology was investigated with the addition of minor alloying elements (Al/Zn) to an Mg-3Ca-2Sn alloy with a lamellar eutectic. Transition in eutectic morphology from lamellar to divorced type was observed with Zn addition in contrast to alloying with Al. Analysis of microsegregation behavior elucidates that Zn has more tendency to partition into the liquid, resulting in higher constitutional undercooling as compared to Al. The Zn addition leads to a decrease in eutectic onset temperature. Higher Ca concentration in liquid along with thin interdendritic regions resulted in the divorced eutectic formation in Mg-3Ca-2Sn-1Zn (XTZ321). © 2018 Elsevier Ltd