Understanding and controlling ductility in nanoscaled metallic glasses

Despite the great potential of bulk metallic glasses (BMG) to be used as structural materials the inverse strength-ductility-functionality problem significantly limits the application of these materials. So far, significant tensile ductility has been reported only for composite materials and microscopic metallic glass samples of around 100 nm. However, experimental studies of the tensile behavior of metallic glass nanowires show a wide range of failure modes, ranging from ductile-to-brittle shear failure. On the other hand, simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce and explain the brittle-like fracture deformation as found in experiments.  By using large-scale molecular dynamics simulations I will provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. Our results explain the ductile-to-brittle transition in terms of critical nanowire aspect ratio and structural rejuvenation process. These results may help to better understand the deformation mechanisms of metallic glass nanostructures and demarcate ductile and catastrophic failure.