This paper examines the effects of stacking fault energy on the micro-and nano-indentation behavior of face-centered-cubic thin films.These include:LIGA nickel MEMS structures,alpha brass,copper and high purity aluminum.The measured hardness are then fitted to a strain gradient plasticity model based on the Taylor dislocation hardening model.Hardness is shown to exhibit a size dependence wtih different characteristic slopes in the micron and nano-scale regimes.Deep indents are shown to exhibit classical linear behavior.However,shallow indents exhibit an abrupt decrease in slope (almost by a factor of 10),giving rise to a bi-linear behavior.Furthermore,as the gradient become less sharp,the trends in the nano-hardness data become similar to those of the microhardness data predicted by the strain gradient plasticity model.Finally,the effects of stacking fault energy are then discussed within the context of cross-slip and hardening associated with Shockly partials.
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