Design and characterization of nano and bimodal structured biodegradable Fe-Mn-Ag alloy with accelerated corrosion rate

Highlights: • Bimodal Fe-Mn-Ag alloy was produced by mechanical alloying and spark plasma sintering. • It shows high strength (722 MPa) and ductility (38%) comparable to stainless steel. • The alloy improved significantly corrosion rate of Fe-based alloys to 0.88 mm/yr. • Bimodal-structure is a novel method to design Fe-based biodegradable alloys. Researchers in biodegradable metals have been putting efforts to accelerate the corrosion of iron-based biodegradable metals. These include by alloying iron with manganese and noble elements such as silver, but further increase to the corrosion rate is still needed. In this study, a set of bimodal nano/microstructured Fe-30Mn-1Ag alloys was prepared through mechanical alloying and spark plasma sintering. The alloys were characterized and tested for their corrosion behavior in Hanks' solution at 37 °C and for their mechanical properties. The bimodal-structured alloy possessed a mixture of austenitic (γ-FeMn) and ferritic (α-Fe) phases, while the nano- and macro-structured ones were essentially composed of γ-FeMn and α-Fe phases, respectively. Addition of 1–3 wt.% of silver into the nanostructured alloy increased its corrosion rate from 0.24 mm/year to 0.33 and 0.58 mm/year for Fe-30Mn-1Ag and Fe-30Mn-3Ag, respectively. Whilst, the bimodal Fe-30Mn-1Ag alloy corroded at a higher rate of 0.88 mm/year. This alloy also possessed an interesting combination of high and low micro-hardness phases that contributed to high shear strength of 417 MPa and shear strain of 0.66. Detailed discussion on the relationship of microstructure with corrosion behavior and mechanical properties is presented in this manuscript.