Significant refinement of coarse (Fe, Mn)Zn13 phase in biodegradable Zn-1Mn-0.1Fe alloy with minor addition of rare earth elements

Zn alloys containing Fe element suffer from the detrimental effect of coarse FeZn(13 )or (Fe, Mn)Zn-13 second phase in Zn matrix on mechanical properties, especially on ductility. The key reasons are the peritectic reaction of Fe and Zn at high temperatures and negligible solid solubility of Fe in Zn at low temperatures. Taking a recently developed biodegradable Zn-Mn-Fe alloy as the base alloy, it is revealed that minor additions of Y and Nd rare-earth elements can significantly refine (Fe, Mn)Zn-13 phase. With a total addition of 0.14%, the average size of blocky (Fe, Mn)Zn-13 particles reduces about 43%, while the average length of lath-like (Fe, Mn)Zn-13 particles reduces about 50%. Sphere-like (Y, Nd)Zn-12 particles serve as effective nucleating agents for (Fe, Mn)Zn-13 and MitZn(13) with nearly the same lattice parameters. As a result, yield strength, the ultimate tensile strength, and elongation to failure of the base alloy increase by 30 MPa, 27 MPa, and 6%, respectively. Cell viabilities of the alloys with or without rare-earth additions are all over 100%, indicating good biocompatibility.