A way by inhomogeneous plastic deformation of metallic glasses to synthesize metallic nanoglasses: A brief review

Nanoglass, which consists of nano-sized glassy regions and glass/glass interfaces, has a completely new microstructure. It can be expected that nanoglasses would be featured with excellent or even unique properties. However, the nanoglass samples synthesized by the traditional method of inert gas condensation (IGC) cannot be made into bulk form (can only be made into a small flake), and there are many holes existing in such samples. The inhomogeneous plastic deformation of metallic glasses (MGs) produces shear bands with a large amount of free volume, which can serve as glass/glass interfaces. Then a dense metallic nanoglass can be synthesized by reducing shear band spacing to nanoscale. Free volume, shear band spacing, orientations and intersections are key factors for synthesizing nanoglass. Although the shear band spacing has been reduced to below 100 nm in several works, the orientations of the reported shear bands are relatively consistent and they are only distributed in a small area of the sample. It is significant to produce a high density of shear bands with severe intersections, and eventually to form a microstructure consisting of nano-sized glassy regions enclosed by shear band networks. Based on these above focus issues, the evolutions of free volume and shear bands in metallic glasses, and the production, structure and properties of metallic nanoglasses produced by inhomogeneous plastic deformation were reviewed.