biostudies-literatureKetkaew JU.S. Department of EnergyU.S. Department of Energy (DOE)Richard F. Goodman Yale/Weizmann Exchange Program3271https://www.ebi.ac.uk/biostudies/studies/S-EPMC6095891biostudies-literatureUnknown9(1)The fracture toughness of glassy materials remains poorly understood. In large part, this is due to the disordered, intrinsically non-equilibrium nature of the glass structure, which challenges its theoretical description and experimental determination. We show that the notch fracture toughness of metallic glasses exhibits an abrupt toughening transition as a function of a well-controlled fictive temperature (Tf), which characterizes the average glass structure. The ordinary temperature, which has been previously associated with a ductile-to-brittle transition, is shown to play a secondary role. The observed transition is interpreted to result from a competition between the Tf-dependent plastic relaxation rate and an applied strain rate. Consequently, a similar toughening transition as a fNature communicationsMechanical glass transition revealed by the fracture toughness of metallic glasses.PMC6095891DE-SC0004889DE-AC02-06CH11357DE-SC0016179Yamada RO'Hern CSPereira GFan MWang HDatye ASchroers JSchwarz UDDmowski WLiu ZBouchbinder EEgami TShattuck MDChen WKetkaew JfalseMechanical glass transition revealed by the fracture toughness of metallic glasses.The fracture toughness of glassy materials remains poorly understood. In large part, this is due to the disordered, intrinsically non-equilibrium nature of the glass structure, which challenges its theoretical description and experimental determination. We show that the notch fracture toughness of metallic glasses exhibits an abrupt toughening transition as a function of a well-controlled fictive temperature (Tf), which characterizes the average glass structure. The ordinary temperature, which has been previously associated with a ductile-to-brittle transition, is shown to play a secondary role. The observed transition is interpreted to result from a competition between the Tf-dependent plastic relaxation rate and an applied strain rate. Consequently, a similar toughening transition as a f2018-01-01T00:00:00Z2018 Aug2025-04-21T17:45:00.369Z2019-03-26T23:54:34ZS-EPMC60958913011591010.1038/s41467-018-05682-8