The role of minor alloying in the plasticity of bulk metallic glasses

Hilke S, Rösner H, Wilde G

Abstract

Micro- or minor alloying of metallic glasses is of technological interest. An originally ductile Pd-based monolithic bulk metallic glass (Pd40Ni40P20) was selectively manipulated by additions of Fe or Co. The alloying effects were extreme, showing either exceptional ductility upon Co addition or immediate catas- trophic failure upon Fe addition when tested under uniaxial compression or 3-point bending. The amor- phous structure was characterized prior to deformation with respect to its medium-range order (MRO) using variable resolution fluctuation electron microscopy (VR-FEM). We observe striking differences in the MRO between the ductile and brittle metallic glasses, with the ductile glasses exhibiting a rich structural diversity and MRO correlation lengths up to 6 nm. The MRO diversity seems to enable easier shear banding and hence enhance the deformability.