Unusual gradient stress induced superior room-temperature plasticity in brittle ferromagnetic bulk metallic glass

Ferromagnetic bulk metallic glasses (FBMGs) possess excellent soft magnetic properties, good corrosion resistance, and high strength. Unfortunately, their commercial utility is limited by their brittleness. In this work, we report the enhancement in the room-temperature plasticity during the compression (25%) and bending flexibility of Fe74Mo6P13C7 FBMG by using water quenching. The high-energy synchrotron X-ray measurements, high-resolution transmission electron microscopy, three-dimensional X-ray microtomography, and finite element simulation were performed to reveal the origin. It was found that the M-shape profile of residual stress improves the mechanical properties of FBMGs, particularly their plasticity. The reversal of the heat-transfer coefficient and cooling rate from the ‘vapor blanket’ to ‘nucleate boiling’ transition during water quenching processing is the main cause of the unusual profile of residual stress in glassy cylinders. Encouraged by the progress in developing flexible silicate glasses, this work highlights a processing method to improve plasticity and surmount technical barriers for the commercialization of FBMGs.