Correlation between Bond Order Based on Electron Theory and Active Corrosion Rate for Ti-based Alloys Attacked in HCl Solution

Abstract

In order to understand alloying effects on the corrosion resistance of titanium, polarization curves were measured at 343 K in 10 mass% HC1 solution with various Ti-M binary alloys ( M= Al, Nb, Ta, Zr, Hf, Fe, V, Cr, Mo, Co and Ni). The results were interpreted using an alloying parameter obtained by a molecular orbital calculation. The parameter is the bond order (Bo) which is a measure of the strength of the covalent bonds between titanium and alloying elements. It was found that alloys containing the elements with higher Bo values showed a lower critical anodic current density in the polarization curve and hence higher corrosion resistance. It is likely that the Bo is a convenient parameter for describing the corrosion rate of titanium alloys in a acid environment such as a hydrochloric acid.

High‐cycle fatigue properties of beta Ti alloy 55Ti–30Nb–10Ta–5Zr, gum metal

“…In addition, they have three characteristic electronic 'magic' numbers. 8,13,16,17 When these three electronic 'magic' numbers are satisfied simultaneously, the excellent properties of gum metal can be obtained. Therefore, under such criteria, various combinations of alloy compositions are available, for example, Ti-23Nb-0.7Ta-2Zr-O and Ti-9Nb-12Ta-3V-6Zr-O, and so on.…”

“…These alloys consist of Group IVa and Va elements in the periodic table of the elements and oxygen, Ti–Nb–Ta–Zr–O alloys. In addition, they have three characteristic electronic ‘magic’ numbers A compositional average valence electron number (electron/atom ratio, e/a) of approximately 4.24.A bond order (BO value) of approximately 2.87, based on the DV‐Xα cluster method, which represents the strength of the covalent bond between titanium and the alloying elements.A ‘d’ electron‐orbital energy level (Md value) of approximately 2.45 eV, representing electronegativity.…”