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A MEMS Tensile Testing Technique for Measuring True Activation Volume and Effective Stress in Nanocrystalline Ultrathin Microbeams

Signature parameters, such as true activation volume and effective stress, are often characterized to identify the governing plastic deformation mechanisms, including that of nanocrystalline metals. The accurate measurement of these parameters using transient tests was recently questioned for nanocrystalline metals, in which grain-boundary-based mechanisms can concurrently occur with dislocation glide. Here, we demonstrate the use of a microelectromechanical systems (MEMS) device to measure true activation volume and effective stress based on repeated stress relaxation and stress dip experiments, respectively. The technique was demonstrated on 100-nm-thick nanocrystalline Au microbeams. These miniaturized tests open up the possibility of observing the mechanisms directly under a transmission electron microscope, and providing a direct link between these measured parameters and the governing mechanisms. [2016-0306]