TY - JOUR A1 - Holzer, Marco A1 - Johansen, Sidsel M. A1 - Christensen, Johan F.S. A1 - Smedskjaer, Morten M. A1 - Cicconi, Maria Rita A1 - de Ligny, Dominique A1 - Müller, Ralf A1 - de Camargo, Andrea S.S. A1 - Maaß, Robert T1 - Direct connection between secondary relaxation mode and fracture toughness in alkali-aluminosilicate glasses N2 - Oxide glasses are intrinsically brittle, lacking sufficient atomic-scale mechanisms that can relax mechanical stresses in the vicinity of a propagating crack. As a result, fracture is typically well-captured by considering local bond rupture at the crack tip. Here we demonstrate that barrier energies related to the low-temperature 𝛾-relaxation mode in alkali-aluminosilicate glasses are inversely related to the fracture toughness measured via standardized three-point bending fracture experiments. This holds true for both a series with varying cations (Li, Na, K) and one with varying Li concentration. The structural rationale for this finding is gained via Raman spectroscopy. The findings suggest that a fundamental structural relaxation mode measured on bulk specimens can serve as an effective guideline for fracture toughness of oxide glasses. Data for additional silicate glasses support this conclusion. KW - Fracture toughness KW - Oxide glass KW - Mechanical properties KW - Alkali-aluminosilicate glasses KW - Internal friction PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-651540 DO - https://doi.org/10.1016/j.mtadv.2025.100669 SN - 2590-0498 VL - 29 SP - 1 EP - 10 PB - Elsevier Ltd. CY - Amsterdam, Niederlande AN - OPUS4-65154 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qu, R. A1 - Maaß, Robert A1 - Liu, Z. A1 - Tönnies, D. A1 - Tian, L. A1 - Ritchie, R. A1 - Zhang, Z. A1 - Volkert, A. T1 - Flaw-insentive fracture of a micrometer-sized brittle metallic glass N2 - Brittle materials, such as oxide glasses, are usually very sensitive to flaws, giving rise to a macroscopic fracture strength that is much lower than that predicted by theory. The same applies to metallic glasses (MGs), with the important difference that these glasses can exhibit certain plastic strain prior to catas- trophic failure. Here we consider the strongest metallic alloy known, a ternary Co 55 Ta 10 B 35 MG. We show that this macroscopically brittle glass is flaw-insensitive at the micrometer scale. This discovery emerges when testing pre-cracked specimens with self-similar geometries, where the fracture stress does not de- crease with increasing pre-crack size. The fracture toughness of this ultra-strong glassy alloy is further shown to increase with increasing sample size. Both these findings deviate from our classical under- standing of fracture mechanics, and are attributed to a transition from toughness-controlled to strength- controlled fracture below a critical sample size. KW - Metallic glass KW - Fracture toughness KW - Size effect KW - Small-scale PY - 2021 DO - https://doi.org/10.1016/j.actamat.2021.117219 VL - 218 PB - Elsevier Ltd. AN - OPUS4-53097 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -