Ultra-stiff metallic glasses through bond energy density design

Abstract

The elastic properties of crystalline metals scale with their valence electron density. Similar observations have been made for metallic glasses. However, for metallic glasses where covalent bonding predominates, such as metalloid metallic glasses, this relationship appears to break down. At present, the reasons for this are not understood. Using high energy x-ray diffraction analysis of melt spun and thin film metallic glasses combined with density functional theory based molecular dynamics simulations, we show that the physical origin of the ultrahigh stiffness in both metalloid and non-metalloid metallic glasses is best understood in terms of the bond energy density. Using the bond energy density as novel materials design criterion for ultra-stiff metallic glasses, we are able to predict a CoTaB short range ordered material by density functional theory based molecular dynamics simulations with a high bond energy density of 0.94 eV Å and a bulk modulus of 263 GPa, which is 17% greater than the stiffest Co-B based metallic glasses reported in literature.

Solid state amorphization in a thin Fe-Si-Mg-O surface film triggered by the reduction of elements from oxides in the temperature range of the α-γ transformation

“…The formation of the atomic structure and its effect on the properties of metallic glass have been studied by a number of researchers so far [3 -5]. Despite the substantial number of currently known chemical compositions of amorphous metallic glasses [6], the development of new ones [7] and the optimization of the known compositions [8] are still of considerable interest.…”

Review on Quantum Mechanically Guided Design of Ultra-Strong Metallic Glasses

“…We found, however, that the valence electron density does not scale universally with bulk modulus for metallic glasses (Schnabel et al, 2017). Schnabel et al (2017) report two different linear relations between B and valence electron density for metalmetal glasses and for metal-metalloid glasses.…”

“…We found, however, that the valence electron density does not scale universally with bulk modulus for metallic glasses (Schnabel et al, 2017). Schnabel et al (2017) report two different linear relations between B and valence electron density for metalmetal glasses and for metal-metalloid glasses. The comparison of density, electronic structure, and bond energy, obtained by integration of the crystal orbital Hamilton population (Dronskowski and Bloechl, 1993), with bulk moduli of different metal-metal and metal-metalloid metallic glasses indicates the bond energy density as the origin of stiffness in metallic glasses (Schnabel et al, 2017).…”

From quantum to continuum mechanics: studying the fracture toughness of transition metal nitrides and oxynitrides

“…However, the required values of surface energy are not present in the literature for these materials at this point. Nevertheless, as the bond energy used in DFT defines both Young's modulus [42] and the surface energy [43], and assuming that the compositioninduced changes in bond energy affect Young's modulus and surface energy with similar trends, then the trend of changes in elastic modulus should also be seen in fracture toughness. Namely, this means lower values of fracture toughness in oxynitrides with respect to nitrides, and that titanium-based coatings should be more brittle than vanadium-based ones.…”