Tailoring The Corrosion Behaviors Of Fe-based And Al-based Metallic Glasses Through Netlike Structure Units

Unlike conventional crystalline materials,the inherent structure of amorphous alloys is a single phase structure with uniform chemical composition;especially due to the absence of dislocations,grain boundaries and second-phase particles,the pitting behaviors of amorphous materials are inhibited and the amorphous with excellent corrosion resistance are applied to anti-corrosion coatings,biological materials and other fields.The studies on the corrosion behavior of amorphous materials are mostly focusing on the composition and the influence of the external field treatment,but the researches from the perspective of atomic clusters are less.We selected Fe87-xNb13Bx(x = 0,7,10 and 13)amorphous alloys with network structure units and Al85Ni10RE5(RE = Y,Gd,La and Ce)amorphous alloys with more Ni-centered TTP clusters(tricapped trigonal prism).The thermodynamic properties were characterized by DSC;the potentiodynamic polarization curves,the EIS(Electrochemical Impedence Spectroscopy)curves and the corrosion resistance were measured by CHI660E work station;the corrosion morphology and corrosion product composition were analyzed by SEM and XPS.Besides,the internal clusters packing of Fe-based amorphous and the interaction between Ni-centered TTP with Cl-and O atom were analyzed by computer simulations.Our researches try to build a bridge between the netlike structures and corrosion resistance in Fe-based and Al-based metallic glasses.In Fe87-xNb13Bx(x = 0,7,10 and 13)metallic glasses,Nb addition enhances the glass forming ability;as CNb hops from 7 to 10 at.%,the glass forming ability is enhanced drastically and meanwhile there exihibits a marked turning point in corrosion resistance between cNb = 7 and 10 at.%,such as the occurrence of wider passive platform in the potentiodynamic plots and the transformation from the nanoscale pitting holes to stable passive films in corrosion morphologies.After heating treatment,the ?-Fe crystallization is retarded and the primary precipitated phases in Fe-Nb-B glasses with CNb = 10 at.%involve(Fe,Nb)23B6 phase.Via ab initio molecular dynamic(AIMD)simulations,the atomic packings in Fe-Nb-B metallic glasses with cNb = 10 and 13 at.%resemble that in Fe23B6 crystalline cell,such as interconnected Nb-Nb pairs/strings,Fe-Nb bond interpenetration and the distorted TTP(tricapped trigonal prism)of B-centered.Thus,the similar Fe23B6 netlike structure yields a marked turning point in corrosion resistance between cNb = 7 and 10 at.%.For the Al85Ni10RE5(RE = Y,Gd,La and Ce)metallic glasses,the typical TTP cluster,which corresponds to the<0,3,6,0>polyhedron,is introduced to probe the corrosion behaviors of metallic glasses,including the pitting and passivation behaviors.The pitting potentials of the Al85Ni10RE5(RE = Y,Gd,La and Ce)metallic glasses in neutal solution exhisit a reverse trend to that in binding energy(Eb)of TTP-C1-,the higher Eb,the less Epit.Thus,the binding energy of TTP-C1-provides an indicator to predict the pitting behavior of AI-Ni-based metallic glasses with different RE addition.In addition,the Gd atom in Gd-containing TTP cluster interacts with C1-and O atom easily.Conversely,in La-cntaining TTP cluster,A1 atoms easily interact with C1-and O atom;these evidences explain why Al85Ni10Gd5 ribbons exhisit higher pitting potential,lower passivation current density than Al85Ni10La5 in neutral solution as well as coaser and denser pitting holes in the corrosion morphology.As a whole,these results not merely have implications for understanding the role of element addition in metallic glasses,but also guide us to tailor the inherent atomic packing of metallic glasses with the superior corrosion resistance to satisfy the environmental condition.