Role of late transition metals on pitting resistance of Zr-Ti-（Cu, Ni,Co）-Al bulk metallic glasses in 0.6 M NaCl aqueous solution

Yu Li^1,2，Jian Xu¹

1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences2. Graduate School, University of Chinese Academy of Sciences

摘 要：Four quanternary Zr-based bulk metallic glasses（BMGs）were selected,including the Zr₄₆Ti₂Cu₄₅Al₇,Zr₆₁Ti₂Cu₂₅Al₁₂,Zr₅₅Ti₄Ni₂₂Al₁₉and Zr₅₅Ti₂Co₂₈Al₁₅,due to their robust glass-forming ability and containing a single species of late transition metal（LTM）in compositions.Their pitting resistances in 0.6 M Na Cl aqueous solution were investigated to examine the role of LTM elements in the alloys,with electrochemical measurements,surface morphology observation and x-ray photoelectron spectrometry analysis.It is shown that in comparision with two Cu-bearing BMGs,Zr₅₅Ti₄Ni₂₂Al₁₉and Zr₅₅Ti₂Co₂₈Al₁₅BMGs exhibited significantly superior resistance to pitting.Zr₆₁Ti₂Cu₂₅Al₁₂,Zr₅₅Ti₄Ni₂₂Al₁₉and Zr₅₅Ti₂Co₂₈Al₁₅BMGs manifested distinct passivation behaviour,because of the formation of surface passive film mainly comprising of Zr O₂,Ti O₂and Al₂O₃.However,no significant differences in the electrochemical resistive properties and thicknesses of passive films were found between Zr₆₁Ti₂Cu₂₅Al₁₂and Zr₅₅Ti₄Ni₂₂Al₁₉BMGs.Nevertheless,at the passive film/metal interface,copper enrichment took place in Zr₆₁Ti₂Cu₂₅Al₁₂,whereas the nickel was slightly deficient at the interface in Zr₅₅Ti₄Ni₂₂Al₁₉.During pitting propagation,selective dissolution of the zirconium,titanium and aluminum over the copper took place in Zr₆₁Ti₂Cu₂₅Al₁₂,but it was not the case in Zr₅₅Ti₄Ni₂₂Al₁₉.For the two Cu-bearing BMGs,reduction of passive base metal elements in composition resulted in local selective dissolution,even absence of the passivation.

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