Strengthening Zn–Ag alloys with Mg addition

Zn–Ag alloys are highly promising materials for fabricating biodegradable orthopedic implants. Nonetheless, they suffer from inferior strength. A Zn–2.5Ag alloy was alloyed with different contents of Mg (0.08, 0.5, and 1 wt.%) and then processed by equal channel angular pressing. Tensile tests and microstructure observation were conducted to investigate the impact of Mg addition on the microstructure and mechanical properties of Zn–2.5Ag alloy. Zn–2.5Ag alloy exhibits an ultrahigh elongation (EL) of 120.4% but a poor yield strength (YS) of 90.1 MPa, because of phase boundary sliding (PBS). Mg addition inhibits PBS and thus dramatically enhances YS but lowers EL. Specifically, YS of Zn–2.5Ag alloys containing Mg of 0.08%, 0.5%, and 1% is 257.0, 291.8, and 322.6 MPa, respectively. The alloys with 0.08% and 0.5% Mg possess an EL of around 30%, while the alloy with 1% Mg has an EL of only 11.0%. YS and EL of Zn–2.5Ag–0.5Mg alloy surpass that needed by orthopedic implants by 45.9% and 106.0%, respectively. Grain refinement strengthening is the main contributor to high strength. It is speculated that deformation twinning suppression and < c + a > pyramidal slip activation contribute to good ductility.