OS5-1-3 Effects of length scale on plastic deformation instability of Cu/Au multilayers

Abstract

Strength and plastic deformation behavior of Cu/Au multilayers with different individual layer thicknesses ranging from submicron to nanometer scale have been studied by using instrumented-indentation. The deformation morphologies around the indents at the sample surfaces and the cross-sections of the multilayers were characterized by scanning electron microscopy (SEM) and focus ion beam. It is found that the hardness increases with decreasing individual layer thickness, and begins to deviate from the Hall-Petch strengthening relationship when the individual layer thickness is less than a certain length scale. Furthermore, significant layer thickness dependent shear banding behavior was observed. Quantitative measurement of the shear band dimensions exhibits that the region of the plastic deformation instability becomes more localized with decreasing the length scale of the multilayers. The mechanisms of strengthening and plastic instability of the material at the nanoscale are discussed.