A good combination of ductility, strength, and corrosion resistance of fine-grained ZK60 magnesium alloy produced by repeated upsetting process for biodegradable applications

Abstract

The Repeated Upsetting (RU) as a powerful severe plastic deformation technique to produce fine-grained thick plates was investigated in the present research. The evolution of microstructure, texture, mechanical properties, and bio-corrosion behavior of ZK60 Mg alloy after applying 3 and 5 passes of RU process were analyzed in detail. Results showed that performing the RU process on the rolled-annealed ZK60 alloy transformed its initial coarse microstructure with a mean grain size of 40 µm to a bimodal microstructure after 3rd pass, and a fine equiaxed grain structure having an average size of about 2.8 µm after 5th pass. The texture of rolled-annealed sample, containing basal components, has been transformed into a shear texture with higher intensity during the RU process. The great improvements of strength after RU were attributed to the finer grain size, while easier activation of basal slip due to the presence of desirable texture component, and uniformly distributed fine second phase particles resulted in larger elongation to fracture. The corrosion resistance of the ZK60 alloy decreased after processing by RU, due to the presence of more non-basal planes in contact with the corrosive solution. Nevertheless, the 3-passed sample can be introduced as a biodegradable Mg alloy for implant applications due to its good combination of acceptable strength, ductility, and corrosion resistance.