Defect-induced ordering and disordering in metallic glasses

On the basis of shear modulus measurements on a Pt-based glass, we calculated temperature dependence of the defect concentration c using the Interstitialcy theory. This temperature dependence is compared with temper-ature dependence of the normalized full width at half maximum (FWHM) & gamma; of the first peak of the structure factor S(q) for the same glass available in the literature. It is found that & gamma; above the glass transition temperature Tg linearly increases with c in the same way for both initial and relaxed (preannealed) samples providing the ev-idence of defect-induced disordering in the supercooled liquid region independent of glass thermal prehistory. For both states of the samples, the derivative d & gamma;/dc is close to unity. Below Tg, the interrelation between & gamma; and c is entirely different for initial and relaxed samples. In the former case, strong defect-induced ordering upon approaching Tg is observed while relaxed samples do not reveal any clear ordering/disordering. Possible reasons for these observations are discussed. To further investigate the relationship between the normalized FWHM and defect concentration, we per-formed molecular dynamic simulation of & gamma; (c)-dependence in a high-entropy FeNiCrCoCu model glass. It is found that & gamma; also linearly increases with c while the derivative d & gamma;/dc is again close to unity just as in the case of Pt-based glass.

Automated summary

This study investigates the relationship between defect concentration and the structure factor of glasses based on shear modulus measurements and molecular dynamics simulation. The results show that defect-induced disordering is independent of glass thermal prehistory above the glass transition temperature, while significant differences exist between initial and relaxed samples below the transition temperature.