Effects Of Si Additions On The Glass Forming Ability And Corrosion Resistance Of Cu-Zr-Al Bulk Metallic Glass

As a new structural material with extremely potential applications, Cu-basedamorphous alloys have excellent mechanical properties and low cost of thepreparation. For the further practical application, it is one of the key issues to improvethe GFA of the Cu-based amorphous alloys, meanwhile, the superior properties werenot affected, such as the corrosion resistance. In this paper, Cu-Zr-Al amorphousalloys have been taken as the research objects. Based on the well known of thecorrosion resistance of these amorpous alloy, the metalloid element Si was added inthe Cu₄₉Zr₄₅Al₆BMG. Then, the effects of Si additions on the GFA, the corrosionresistance and related mechanism of Cu₄₉Zr₄₅Al₆have been studied. The main resultsare as follows:（1） In1mol/L HCl solution, compared with Cu_49-xZr₄₅Al_x（x=6、8and10, inatom percent）alloy, the corrosion potential of amorphous alloys with the samecomposition is negative, but the current density is low. In3.5%mass NaCl solution,compared with Cu_49-xZr₄₅Al_x（x=6、8and10, in atom percent）alloy, the corrosionpotential of amorphous alloys with the same composition ispositive and the currentdensity is also low. In the above two solutions, with the content of Al increasing, thecorrosion potential becomes negative. In0.5mol/L H₂SO₄solution, corrosion rate ofthe amorphous alloy is lower than that of the alloy with the same composition. Fromthe polarization curves, it can be found that amorphous alloy has ralertively lowercurrent density and passive current density. Cu₄₉Zr₄₅Al₆amorphous alloy has mostpositive corrosion potential and smallest current density and passive current density,the values are-0.184V,1μA/cm²and1.54μA/cm², respectively. In1mol/L HClsolution, Cu47Zr45Al8amorphous has the maximum impedance value. In3.5%massNaCl solution, the impedance value of Cu₄₉Zr₄₅Al₆amorphous alloy is largest in allthe alloys.（2） The addition of0.5-1.0at%Si into the Cu₄₉Zr₄₅Al₆BMG to partly substituteCu can increase both ΔTx and γ, indicating that the GFA of the BMG is promoted byadding Si to substitute Cu in the Cu₄₉Zr₄₅Al₆alloy as the Si content equals or lowerthan1%. However, as the Si content is higher than1%, the GFA of the alloy decreases,and the2-3at%Si additions result in the formation of some intermetallics in the alloy.（3） The0.5-1.5%Si containing Cu-based BMGs exhibit lower corrosion rate andlower Ip, Icorrand higher Rp than Si-free Cu50Zr45Al6BMG in1mol/L HCl,3.5%massNaCl and0.5mol/L H₂SO₄solutions. Thus, the addition of0.5-1.5%Si can effectively promote the corrosion resistance of the Cu₄₉Zr₄₅Al₆BMG in the three corrosion media.The improvement of the corrosion resistance may be attributed to the formation of thesilica containing passive layer on the surface of the BMG.（4）In the solution containing Cl^-, Annealing treatment under the conditions of aappropriate temperature and soaking time improves the corrosion resistance ofCu₄₈Zr₄₅Al₆Si₁amorphous alloy.