Fig. 1 Schematic representation of the heat treatment operations

Fig. 2 Schematic diagram of the antibacterial test

Fig. 3 SEM images of the solution-treated a TZ, b TZC-3, c TZC-5, and d TZC-7 alloys

Fig. 4 SEM images of TZ, TZC-3, TZC-5 and TZC-7 alloys solution-treated and aged (STA) at a-d 450 °C for 10 h, e-h 540 °C for 6 h, and i-l 660 °C for 4 h, respectively

Fig. 5 X-ray diffractograms for the solution-treated and aged TZ, TZC-3, TZC-5, TZC-7 alloys at a 450 °C for 10 h, b 540 °C for 6 h, and c 660 °C for 4 h, respectively

Fig. 6 Ultimate tensile strengths, yield strengths and elongations of the TZ and TZC alloys: a solution-treated at 1050 °C, b solution-treated and then aged at 450 °C for 10 h, c solution-treated and then aged at 540 °C for 6 h, and d solution-treated and then aged at 660 °C for 4 h

Fig. 7 Hardness values of the ST and STA alloys at various conditions. Inset: representative indentation of alloys’ microstructures at ST and STA conditions showing martensite-like parallel and shiny marks for the ST and dimple-like dull marks for the STA alloys, respectively

Fig. 8 Representative photographs of the typical S. aureus colonization behavior on the various solution-treated and then aged (STA), a TZ, b TZC-3, c TZC-5, d TZC-7, e blank control at 450 °C for10 h, f TZ, g TZC-3, h TZC-5, i TZC-7, j blank control at 540 °C for 6 h, k TZ, l TZC-3, m TZC-5, n TZC-7, p blank control at 660 °C for 4 h, and q the respective antibacterial rates of the corresponding alloys at different conditions

Fig. 9 Potentiodynamic polarization curves for the solution-treated and aged TZ, TZC-3, TZC-5, TZC-7 alloys at a 450 °C for 10 h; b 540 °C for 6 h, and c 660 °C for 4 h, respectively

Fig. 10 Concentration of Cu ions released (in mg/L) from differently aged TZ, TZC-3, TZC-5 and TZC-7 alloys over a 35-day period showing that the minimum lethal dosage threshold (LD 50) is not crossed