Gradient Confinement Induced Uniform Tensile Ductility in Metallic Glass

Metallic glass (MG) generally fails in a brittle manner under uniaxial tension loading at room temperature. The lack of plastic strain of MG is due to the severe plastic instability via the easily formed one dominate shear band. There have been several approaches to improve the ductility in MG, but achieving uniform tensile ductility for monolithic MG in bulk size remains a challenge. Here we demonstrate a uniform tensile ductility of 12% achieved in a micrometer scale Ni-P amorphous film coated on a Ni substrate with gradient structure. Instead of a single run-away shear band, such a gradient structure generates massive extensive multiple shear bands in the film, leading to a record high tensile ductility in MG. The present finding highlights a novel route for achieving uniform tensile ductility in monolithic metallic glass with bulk size.