Unusual strain rate sensitivity of nanoscale amorphous CuZr/crystalline Cu multilayers

Nanoscale amorphous CuZr/crystalline Cu multilayers were synthesized to study their strain rate sensitivity and plastic deformation mechanisms via nanoindentation testing. Despite the dramatically reduced microstructural length scale, nearly constant strain rate sensitivity of the multilayers was obtained at a wide range of individual layer thickness (10~100 nm). The scenarios that the two constituent layers mutually confined by each other might exhibit quite different strain rate sensitivities relative to the monolithic ones were proposed. Specifically, compared with the monolithic Cu and CuZr layers, respectively, the confined Cu layers should exhibit gentler increases in strain rate sensitivity while confined CuZr layers exhibit reduced strain rate sensitivity, as Cu layer thickness decreases. Correspondingly, corresponding deformation mechanisms accommodating the co-deformation of the two constituent layers were discussed in detail.