Impact of Zn and Ca on dissolution rate, mechanical properties and GFA of resorbable Mg-Zn-Ca metallic glasses

This article presents investigations utility of Mg-based metallic glasses for resorbable orthopedic implants. Exploration of biocompatible Mg-Zn-Ca alloys in order to determine Zn and Ca optimum concentration were conducted, based on three criteria: sufficiently high GFA (glass forming ability), sufficiently high tensile strength, microhardness and the suitable dissolution rate (corrosion rate) in Ringer's solution. Fulfillment of these criteria should ensure bone union before implant dissolution. The optimatization of Ca and Zn concentration in the range of 4-6 at.% Ca and 28-32 at.% Zn was executed. The samples in form of ribbons (0.02-0.05 mm thickness) and rods (about diameter up to 4 mm) with amorphous structure were produced. These investigations allowed to determine the GFA. The optimal results for Mg66Zn30Ca4 and Mg64Zn32Ca4 alloys: tensile strength: 191-166 MPa, microhardness: 291-263 HV and volume of released hydrogen 0.04-0.12 ml/cm2/h. The corrosion studies - immersion and potentiodynamic methods were conducted (including measurement specific corrosion current density for Mg alloys). Finally, a comparative analysis was performed, which indicated the impact of Ca and Zn concentration on: GFA, mechanical properties and dissolution rate of studied metallic glasses.