Nanotwin-assisted grain growth in nanocrystalline gold films under cyclic loading

Abstract

Under mechanical loading, nanocrystalline metals show unique behaviour, among the most common of which are high strength, mechanically induced grain growth and twin formation. However, mechanically induced grain growth is seldom correlated with twins. Here we report a clear relationship between grain growth and nanoscale twins in 20-nm-thick gold films with a grain size of B19 nm under cyclic loading based on atomic-scale observations and analyses. We find that the formation of nanotwins is an effective way to assist grain coarsening, following a fundamental process that the mutual formation of nanotwins in two neighbouring grains changes the local grain orientation and dissociates the grain boundary into new segments, which become more mobile. The proposed mechanism of nanotwin-assisted grain growth may have important implications for understanding the interface-mediated mechanisms of cyclic plastic deformation and for the interface engineering design of nanostructured metals with both high strength and good fatigue resistance.

Twinning/detwinning-mediated grain growth and mechanical properties of free-standing nanotwinned Ni foils: Grain size and strain rate effects

“…From the HRTEM images Fig. 7(d), (f) and (h) in (c) marked 1, 2 and 3, respectively, we can clearly see that GBs are dissociated by twinning and become blurred, and would finally vanish, causing grain coarsening, similar to NC-Au with medium SFE under cyclic loading [79]. During plastic deformation, twins successively formed (see G2 and G3 in Fig.…”

Initiation and stagnation of room temperature grain coarsening in cyclically strained gold films

“…Mechanically induced grain coarsening has been observed in a large variety of materials at room temperature [20][21][22][23][24][25][26][27][28][29][30][31][32]. Although GB migration and grain coarsening are closely related and are often mentioned in the same context, it is important to highlight an important difference between these two processes.…”

PtAg bimetallic nanowires: Facile synthesis and their use as excellent electrocatalysts toward low-cost fuel cells

“…The grain boundary and lattice defect are not obvious if two primary particles attach and grow together via the (100) facet matching growth mode ( Figure 3B). As a result, when additional particles continually attach to the existing nanostructure, linear and bending morphology can be obtained following the two matching modes, which are thermodynamically driven by minimizing the interface mismatch energy via forming a coherent interface to reduce the exposed surface area [47,48]. The fast Fourier transform (FFT) (inset in the middle) from the selected area of nanowires shows diffraction pattern, and it has the same symmetry as fcc Pt or Ag.…”