Inhomogeneous deformation in metallic glasses

In metallic glasses, the combination of metallic bonding with an amorphous structure gives excellent mechanical properties such as high yield stress and yield strain compared with conventional polycrystalline alloys. It is, therefore, of great interest to exploit bulk metallic glasses ( BMGs) as structural materials, particularly as many are now available in bulk form. The plastic deformation of BMGs is generally inhomogeneous, severely localised into shear bands with a characteristic thickness of only similar to 10 nm. This shear instability is associated with work softening and impedes the exploitation of the otherwise desirable mechanical properties of metallic glasses in structural applications. Recent progress in understanding work softening in metallic glasses and the consequent formation of shear bands is reviewed, considering both experimental work and molecular dynamics simulations. The basic phenomena of plastic deformation in BMGs are briefly introduced. The initiation of shear bands, their propagation, and associated structural changes within the bands are considered. Recent advances in tailoring the microstructure of metallic glasses to increase their plasticity are also presented. The mechanisms of forming shear bands in different material systems are compared, highlighting the distinct plastic deformation mechanisms in BMGs.