Study On The Corrosion Resistance Mechanism Of Cu-Zr Based Amorphous Alloys Based On Fermi Level

Microalloying can have a significant effect on the properties of amorphous alloys.But at present,it is still insufficient to know the microscopic mechanism that microalloying elements affecting the corrosion resistance of amorphous alloys.In this paper,simple metal Zr and Cu50Zr50 amorphous alloys as research basis,we studied how the microalloying elements(Nb,Y,Ti,Ta,Ni,Ag)affect the corrosion resistance of alloys in NaCl and NaOH corrosive liquid.The XRD was applied to detect the structure of alloys.The corrosion resistance of alloys in each corrosive liquid was analyzed by polarization curve.The formation rate of passive film was tested by Amperometric i-t curve.The composition of passive film on sample surface was analyzed by EDS.Using the CASTEP module in Materials Studio to calculate the Fermi energy level and bond energy of the sample after microalloying.The microcosmic mechanism of how microalloying elements affect corrosion resistance was studied by metal bond theory and principle of similar energy.How the microalloying elements(Nb,Y,Ti,Ta,Ni,Ag)affect the corrosion resistance of simple metal Zr was studied,and it is found that the Fermi level was changed due to addition of microalloying elements.Then the ionization energy and bonding energy of matrix atom were altered.It led that chemical reaction rate in the passivation process was changed,and then the formation rate of passive film was reformed.Finally,the corrosion resistance of matrix was influenced.For Cu50Zr50 amorphous alloys,Pauling's theory of the metallic bond,principle of similar energy and orbital energy show that the element of Nb,Ti and Y preferentially combine with Zr elements to form metallic bonds,and the Fermi level of Zr was improved.The ionization energy and bonding energy of Zr were lowered indirectly.It led that the formation rate of passivation film was increased.Then the proportion of passivation film with ZrO2 as the main component was increased.Finally,the corrosion resistance of Cu50Zr50 amorphous alloys were improved in 3.5%NaCl and 1 mol/L NaOH solution.The element of Ta,Ni and Ag preferentially combine with Cu elements to form metallic bonds,the ionization energy and bonding energy of Cu were lowered indirectly.The CuO is easily dissolved in the Cl-corrosive environment and some Cu produce precipitates of Cu(OH)2 in an alkaline corrosive environment.The proportion of passivation film with ZrO2 as the main component was increased too.Finally,the corrosion resistance of CusoZrso amorphous alloys was also improved in 3.5%NaCl and 1 mol/L NaOH solution.In this paper.the influence mechanism which the microalloying elements affect the corrosion resistance of amorphous alloys was studied from the atomic scale.It provides the new theoretical guidance to improve the corrosion resistance of amorphous alloys.This is great significance to enlarge the application of amorphous alloys in anti-corrosion materials.