Probing Plasticity Mechanisms in Low Melting Temperature Metallic Nanostructures Using Synchrotron X-Ray Microdiffraction

Abstract

A nondestructive ex situ Synchrotron Laue X-ray Microdiffraction (µSLXRD) technique is used to investigate the plasticity mechanisms in the metallic nanostructures and their evolution at high homologous temperatures through analyzing low melting temperature metals such as tin. Without the use of expensive high temperature equipment, the current approach of studying plasticity mechanisms at high temperature is enabled by the low melting behaviors of the samples allowing them to provide insights on high temperature deformation mechanisms, such as thermally activated dislocation climbs. Nanopillars with a diameter near 1µm were deformed by uniaxial compression to strains of in excess of 20% at a strain rate of approximately 0.001s-1. Defect density evolution in the nanopillars was evaluated by synchrotron Laue X-ray microdiffraction (µSLXRD) before and after deformation (ex situ). It was found from the Laue peak broadening measurements that there was no significant change in the dislocation density of the same pillar before and after such an extent of deformation. These findings were being compared to similar experimental results of indium and gold nanopillars (from our previous reports). They were found to be in stark contrast to our previous results with indium (although both are low melting temperature metals) where the synchrotron Laue X-ray microdiffraction showed significant peak broadening – before vs. after the uniaxial compression to a similar amount of deformation. It appears high temperature plasticity mechanism in tin nanostructures involves significant lattice diffusion behavior, as opposed to simple displactive behavior (through dislocation movements) that has been proposed in recent studies of tin nanostructures.