Introducing a strain-hardening capability to improve the ductility of bulk metallic glasses via severe plastic deformation

The great technological potential for bulk metallic glasses (BMGs) arises primarily because of their superior mechanical properties. To realize this potential, it is essential to overcome the severe ductility limitations of BMGs which are generally attributed to shear localization and strain softening. Despite much international effort, progress in improving the ductility of BMGs has been limited to certain alloys with specific compositions. Here, we report that severe plastic deformation of a quasi-constrained volume, which prevents brittle materials from fracture during the plastic deformation, can be used to induce strain hardening and to reduce shear localization in BMGs, thereby giving a significant enhancement in their ductility. Structural characterizations reveal the increased free volume and nanoscale heterogeneity induced by severe plastic deformation are responsible for the improved ductility. This finding opens a new and important pathway towards enhanced ductility of BMGs.The authors are grateful for the scientific and technical input and support from the Australian Microscopy & Microanalysis Research Facility node at the University of Sydney. This research was financially supported by the Australian Research Council. MK and TGL were supported by the National Science Foundation of the United States under Grant No. DMR-0855009 and by the European Research Council under ERC Grant Agreement No. 267464-SPDMETALS. ZWS was supported by NSFC (50925104) and the 973 program of China (2010CB631003)