Methods: The AISI 2205 stainless steel with 0.1, 0.2 and 0.3wt.% Ag alloys were tested in this study. The specimens for optical microscopy and scanning electron microscopy observations were prepared by sectioning, mounting, polishing and etching. A JEOL-2100 transmission electron microscopy equipped with an energy-dispersive X-ray spectrometer was employed to identify the phase structure and chemical compositions. Moreover, the antibacterial testing was performed according to JIS Z2801:2010 specification using Gram-positive bacterial Staphylococcus aureus) and Gram-negative bacterial Escherichia coli.
Results: As the alloy with 0.1 ~ 0.3wt.% Ag contents underwent solution heat treatment (SHT), the microstructure of the alloys was a mixture of (α + γ + Ag-rich compound)-phases. The amounts of α phase and Ag-rich compound increased as increasing Ag contents. The Ag-rich compound belongs to a face-center-cubic structure with the lattice parameter a = 0.251 nm. No other precipitates were found within the matrix and grain boundaries in the present alloys after SHT. The results of an antibacterial test revealed that the Ag-rich compounds play a key role in the antibacterial mechanism of Ag-incorporated alloys.
Conclusions: As AISI 2205 alloy has a Ag content ≥ 0.2 wt.%, it will have excellent antibacterial properties against both Staphylococcus aureus and Escherichia coli, with an antibacterial rate of nearly 100%.