Project Summary:

The design of high-performance structural thin films consistently seeks to achieve a delicate equilibrium by balancing outstanding mechanical properties like yield strength, ductility, and substrate adhesion, which are often mutually exclusive. Metallic Glasses (MGs) with amorphous structure have superior strength (close to the theoretical atomic decohesion limit), but usually poor ductility with catastrophic failure induced by the formation of thin (~10 nm) shear bands (SBs), hindering their application as structural materials. Therefore, improving the plasticity of MGs has been a long-standing goal for several decades and currently object of intense research. Introducing local heterogeneities at the atomic level, involving the addition of non-metallic elements and presence of nano-interfaces with large free volume, has been found an effective way to control MGs mechanical properties with the possibility to deflect and defer the propagation of SBs during deformation, thus enhancing ductility and promoting a more homogeneous deformation. Nevertheless, a SB engineering approach is still not well-developed with often a trial-error approach and a poor physical understanding, resulting in limited control of the mechanical behavior. Specifically, key questions about the interplay between the local chemical heterogeneities (such as the addition of covalent elements) or the control of free volume is still at its infancy, preventing applications of MGs in the field of structural coatings and microelectronics.