Effects of noble elements on the glass-forming ability, mechanical property, electrochemical behavior and tribocorrosion resistance of Ni- and Cu-free Zr-Al-Co bulk metallic glass

In this study, the influences of Pd, Au and Pt on the glass-forming ability (GFA), mechanical property, electrochemical behavior and tribocorrosion resistance of the Ni- and Cu-free Zr53Al16Co31 bulk metallic glass (BMG) were investigated. Alloying of noble elements enhances the GFA and the Zr53Al16Co26M5 (M = Pd, Au and Pt) BMGs with a diameter of 5 mm can be fabricated by copper mold casting. The ZrAlCo-based BMGs show a good combination of mechanical properties with a high yield strength of over 2000 MPa, low Young's modulus of about 93 GPa and high hardness of over 550 HV. Pd, Au and Pt take a significant influence on the corrosion resistance of the ZrAlCo-based BMGs in phosphate buffer saline (PBS) solution. The ZrAlCoPt alloy exhibits the highest corrosion resistance whereas ZrAlCoAu displays the lowest one, which can be correlated with their Zr and Al concentration in the surface passive film of alloys. The ZrAlCo-based BMGs illustrate a lower wear resistance in PBS solution than that in air, which is attributed to the synergistic effects of abrasive and corrosive wear. The wear resistance of ZrAlCo-based BMGs in PBS solution highly corresponds to their corrosion resistance. The ZrAlCoPt alloy demonstrates the highest tribocorrosion resistance while ZrAlCoAu shows the lowest one among these four ZrAlCo-based BMGs. The possible mechanism of corrosion accelerating wear deterioration is discussed, which provides the guidance for the improvement in the tribocorrosion resistance of Zr-based BMGs for their promising biomedical applications.