Abstract
The unique distribution of grain boundaries (GBs) and grains in nanocrystalline metals makes it interesting to study the mutually exclusive properties of modulus and damping. This study carried out large-scale calculations about the grain size effects through molecular dynamics and comprehensively analyzed the static modulus and damping properties of nanocrystalline metals using the loss modulus as the merit value. The research reveals that as grain size increases, the dissipation in polycrystalline metals transitions from being dominated by GB sliding in small grains to being jointly dominated by GB sliding and intragranular dislocation in larger grain structures. This transition is similar to the one observed in plastic flow stresses in nanocrystalline materials under finite deformation, i.e., the transition from the inverse Hall-Petch mechanism to the Hall-Petch mechanism. The mechanistic conversion of these two dissipations is demonstrated by quantitative characterization. This study is instructive for the mechanical design and development of nanocrystalline metals.
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