Detecting grain rotation at the nanoscale

Abstract

Significance The plastic deformation of nanomaterials has long been wrapped in mystery. Grain rotation is suggested to be a dominant mechanism of plastic deformation for ultrafine nanomaterials. However, the in situ observation of grain rotation has been made possible only for coarse-grained materials. Here we report the in situ high-pressure detection of grain rotation at the nanoscale. The surprising observation is that the texture strength of the same-sized platinum drops rapidly with decreasing grain size of the nickel medium, indicating that more active grain rotation occurs in the smaller nickel nanocrystals. Insight into these processes provides a better understanding of the plastic deformation of nanomaterials at a few-nanometer length scale.

Effects of grain size on tensile fatigue life of nanostructured NiTi shape memory alloy

“…In particular, both dissipated energy (the stress-strain hysteresis loop area D) and the temperature dependence of phase transition stress ( dT d /  ) decrease rapidly with GS, and cyclic stability is enhanced significantly with GS reduction. It is shown that such significant GS effects is primarily caused by the gradual dominance of interfacial energy terms (of grain boundary and phase boundary) in the energetics of the polycrystalline system [32][33][34].…”

Reversal in the Size Dependence of Grain Rotation

“…However, the grain rotation mechanism remains elusive because several processes such as curvature-driven GB migration, lattice diffusion, dislocations, and disclinations may play roles that complicate investigations on the grain rotation mechanisms [17][18][19]. Based on the Read-Shockley model, the conventional belief is that GB-mediated mechanisms dominate the plastic deformation of nanomaterials, resulting in an enhancement in the grain rotation activity of fine nanocrystals [20][21][22][23], i.e. smaller grains rotate more under stress [4,15,24].…”

Radial X‐Ray Diffraction Study of Superhard Early Transition Metal Dodecaborides under High Pressure

“…This plateau is then followed by a decrease at pressures higher than ≈50 GPa, indicating a strain softening phenomenon. This may due to the grain boundary sliding or grain rotation at such high pressures . Alternatively, the stress may be released through a new slip system enabled by pressure‐induced bond rearrangement, a phenomenon previously observed by our group for WB 4 .…”