Effect of Sub-Tg Annealing on the Corrosion Resistance of the Cu-Zr Amorphous Alloys

Despite the economy of material cost and excellent toughness of Cu-based amorphous alloys, especially Cu50Zr50, their poor corrosion resistance to a chloride medium limits their widespread applications. In this study, corrosion tests were performed on the Cu50Zr50 amorphous alloy with different degrees of short-range order, which were prepared by annealing below the glass transition temperature (T-g). It was found that the corrosion resistance of amorphous alloys is improved to a significant level when the alloys were heated below T-g. Calorimetric studies showed that thermally activated relaxation process of created disorder, which occurs during sub-T-g annealing, is responsible for the improvement in the corrosion resistance. Molecular dynamics simulations performed on the Cu-Zr amorphous alloys demonstrated that the relaxation process of the alloys is associated with the formation of energetically stable icosahedra and icosahedron-like structures. Our study highlights the effects of sub-T-g annealing on the improvement in the corrosion resistance of the amorphous alloys from the viewpoint the relaxation process of the short-range orders.