Strain rate sensitivity of Cu/Ta multilayered films: Comparison between grain boundary and heterophase interface

Grain boundaries and heterophase interfaces both play important roles in enhancing the strain rate sensitivity (SRS) of engineering materials as they often serve as obstacles for dislocation motion. In this work, however, we carried out nanoindentation tests on Cu/Ta multilayers prepared with a wide range of modulation periods (Λ) and modulation ratios (η) and found negative contribution of incoherent interfaces to SRS. Activation event extension aided by incoherent interface shear was suggested as the dominating mechanism for rate related deformation process in Cu/Ta multilayers. The results provided valuable insights into the fundamental roles of grain boundaries and heterophase interfaces in plastic deformation.