Figure 4

To account for potential stress effects on viscosity, the results are plotted as strain-rate versus stress in (a).

The color scale indicates the log of viscosity. Here the results from all samples are plotted together. To emphasize possible non-Newtonian behavior the highest and lowest iso-viscosity points are highlighted. The dashed lines represent a polynomial fit to these points to guide the eye. A slope of 1, which indicates Newtonian behavior, is provided as a reference. To clarify the behavior observed in (a) we consider only samples subjected to load jump tests. A representative result from a load jump test on a single nanowire is provided in (b), as a function of increasing power (each symbol type indicates steady state at different power dissipation). Each segment is further labeled with its average viscosity. In addition, simple fits are shown to help approximate the strain-rate sensitivity, m. The slope of the simple fit is used as an approximated strain-rate sensitivity. The fits are colored according to the threshold used to determine the transition from Newtonian (m > 0.7) to non-Newtonian flow (m < 0.7). Micrographs showing the representative failure morphologies due to (c) necking down to a sharp point, denoted as a diamond and (d) shear dominated failure, denoted as a triangle, are included. Such morphologies are indicative of Newtonian and non-Newtonian deformation respectively.