Electronic structure based design of thin film metallic glasses with superior fracture toughness

Materials and design 186, 108327 - (2020). doi:10.1016/j.matdes.2019.108327
High fracture toughness is crucial for the application of metallic glasses as structural materials to avoid catastrophicfailure of the material in a brittle manner. One fingerprint for fracture toughness in metallic glasses isthe fraction of hybridized bonds, which is affected by alloying Pd57.4Al23.5Y7.8M11.3 with M = Fe, Ni, Co, Cu, Os,Ir, Pt, and Au. It is shown that experimental fracture toughness data is correlated to the fraction of hybridizedbondswhich scalewith the localized bonds at the Fermi level. Thus, the localized bonds at the Fermi level are utilizedquantitatively as a measure for fracture toughness. Based on ab initio calculations, the minimum fraction ofhybridized bonds was identified for Pd57.4Al23.5Y7.8Ni11.3. According to the ansatz that the crystal orbital overlappopulation at the Fermi level scales with fracture toughness, for Pd57.4Al23.5Y7.8Ni11.3 a value of around 95 ±20 MPa·m0.5 is predicted quantitatively for the first time. Consistent with this prediction, in micro-mechanicalbeam bending experiments Pd57.4Al23.5Y7.8Ni11.3 thin films show pronounced plasticity and absence of crackgrowth.
Published by Elsevier Science, Amsterdam [u.a.]