Dual alloying improves the corrosion resistance of biodegradable Mg alloys prepared by selective laser melting

Mg alloys have been regarded as revolutionary metallic biomaterials for biodegradable bone implants, but their applications are mainly blocked by the too rapid degradation in physiological environment. This study explores the dual alloying effects of Mn and/or Sn on the performance of Mg alloys prepared by selective laser melting. The observed microstructure indicated remarkable refinement of both the grains and intermetallic phases in the Mn- and/or Sn-containing alloys during the rapid solidification process. Moreover, approximately a half decrease in corrosion rate was observed for AZ61–0.4Mn-0.8Sn alloy with respect to AZ61 alloy. The improved corrosion behavior was primarily due to the enhanced protective effects of surface layers, in which Mn- and/or Sn-rich phases acted as a helpful barrier against medium penetration and thereby alleviated the current exchange with the matrix. In addition, the solute Mn and/or Sn positively shifted the corrosion potential, which also brought about a better corrosion resistance. Furthermore, the strength and hardness of the alloys were also effectively improved and comparable to those of cortical bone. This could be ascribed to the dissolved Mn and/or Sn atoms and the finely dispersed intermetallic phases, which might cause lattice distortion and precipitation hardening. Besides, the Mn- and/or Sn-containing alloys showed good cytocompatibility as indicated by the normal morphology and increased viability of MG-63 cells. These findings suggest that the developed AZ61-Mn-Sn alloy is a promising candidate for biodegradable bone implants.