Size-dependent strain rate sensitivity and interface structure influenced deformation mechanisms in Ti/Ta and Ti/Zr multilayers

The nanostructured Ti/Ta and Tigr multilayers with equal layer thicknesses h ranging from 2.5 to 150 nm were prepared by using magnetron sputtering technique. Their rate dependent deformation behaviors were explored by nanoindentation. With reducing h, the strain rate sensitivity m of Ti/Ta multilayers decreased from a positive value to negative at the critical h* of similar to 20 nm, at which the hardness is insensitive to strain rate. While the m of Tigr multilayers decreased as the decreasing of h. This evolution of strain rate sensitivity in multilayers was interpreted in terms of the heterogeneously interfacial structure, i.e., the constituent interlayer coherent interfaces and phase boundaries in nanolayers. The deformation morphologies after nanoindentation were observed and discussed to further examine plastic deformation and dislocation activities of multilayers. (C) 2022 Elsevier B.V. All rights reserved.