Effects of Si Additions on the Glass-Forming Ability and Corrosion Resistance of Cu₄₉Zr₄₅Al₆ Bulk Metallic Glass Available to Purchase

Alloys with the compositions of Cu_49-xZr₄₅Al₆Si_x (x = 0, 0.5, 1, 2, and 3, in atom percent) were prepared by sucking the melt into a water-cooled copper. The effects of Si additions on the glass-forming ability (GFA) and corrosion behaviors in 1 N hydrochloric acid (HCl), 3.5 mass% sodium chloride (NaCl), and 0.5 N sulfuric acid (H₂SO₄) solutions were studied. It was found that, by adding 0.5% to 1% Si to substitute Cu in the Cu₄₉Zr₄₅Al₆ alloy, the GFA was promoted, but extensive Si addition (>1%) decreased the GFA of the Cu₄₉Zr₄₅Al₆ alloy. The results of weight-loss measurements, electrochemical polarization tests, and electrochemical impedance spectroscopy (EIS) tests on the Cu-based bulk metallic glasses (BMG) with different Si additions revealed that the Si addition improves the corrosion resistance in 1 N HCl, 3.5 mass% NaCl, and 0.5 N H₂SO₄ solutions, especially in 1 N HCl. The improvement of the corrosion resistance may be attributed to the formation of a silica-containing inner layer.