Grain size-dependent delay of avalanches during void evolution in a nanocrystalline Ni

H Li and Y Chen and L Zhao and HJ Li and HX Zong and S Han and JS Lian and XZ Liao and XD Ding and J Sun, SCRIPTA MATERIALIA, 248, 116124 (2024).

DOI: 10.1016/j.scriptamat.2024.116124

The effect of grain size on the underlying dynamics of void evolution in a nanocrystalline (NC) Ni was dissected. Multiscale characterizations reveal that, unlike the suppression of void nucleation by the compressive stress in coarse-grained Ni, dispersive nano- and micro- voids formed readily in NC Ni during compression. Acoustic emission measurements and molecular dynamic simulations demonstrate that the unique structural features and deformation mechanics implicitly occurring in NC metals play multifaceted roles during void evolution. Although the presence of excessive nucleation sites, such as grain boundaries and triple junctions, together with the activation of intergranular plasticity facilitate void nucleation, high interface population retards dislocationdriven void expansion, resulting in sluggish void growth and a corresponding delay of coalescence avalanches.

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