Nanoindentation experiments performed in 5 and 18 lm thick vapor deposited polycrystalline lithium films at 31°C reveal the mean pressure lithium can support is strongly dependent on length scale and strain rate. At the smallest length scales (indentation depths of 40 nm), the mean pressure lithium can support increases from ;23 to 175 MPa as the indentation strain rate increases from 0.195 to 1.364 s À1. Furthermore, these pressures are ;46-350 times higher than the nominal yield strength of bulk polycrystalline lithium. The length scale and strain rate dependent hardness is rationalized using slightly modified forms of the Nabarro-Herring and Harper-Dorn creep mechanisms. Load-displacement curves suggest a stress and length-scale dependent transition from diffusion to dislocation-mediated flow. Collectively, these experimental observations shed significant new light on the mechanical behavior of lithium at the length scale of defects existing at the lithium/solid electrolyte interface.

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This paper studies the correlation between the microstructure and the mechanical properties at the nanometric length scale of individual WC grains as well as the metallic cobalt binder in cemented carbide systems. The local crystallographic orientation has been determined by electron backscattered diffraction and the microstructural analysis has been performed using field emission scanning electron microscopy. Small-scale hardness and elastic modulus have been assessed by means of high speed massive nanoindentation and subsequent statistical analysis. The attained mechanical property mappings present a clear correlation between local hardness and stiffness with chemical nature for each constitutive phase as well as with the crystallographic orientation for the WC particles. Besides expected findings associated with individual phases, such as clear anisotropy of the ceramic phase (basal plane being harder and stiffer than the prismatic one) and relatively high flow stress for constrained binder, the protocol implemented provides novel information on local mechanical response at interfaces between ceramic particles with different orientations as well as regions within the metallic cobalt binder close to the WC-Co interface.

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