Nowadays, Mg and its alloys have attracted much attention because of their excellent biocompatibility and biodegradability. High anisotropy of Mg crystal structure, however, limits the movement of some slip systems; therefore, pure magnesium possesses poor ductility and/or toughness. Lots of studies revealed that alloying of solute elements and modification of grain structure improved the drawbacks. In this study, to clarify the effect of adding solute elements, e.g., Ca and Zn, impact toughness testing and first-principles calculations of generalized stacking fault energy were conducted. For example, alloying magnesium with Ca and Zn and controlling the microstructure produced a Mg alloy with a high compressive fracture strain of 0.40, which was greater than the estimated maximum strain for fastening a surgical clip. This high fracture strain arose from the enhanced grain boundary cohesive energy and reduced anisotropy of slip systems by solute segregation. As a result, the alloy successfully occluded blood vessels.