Interactions between Dislocations and Penta-Twins in Metallic Nanocrystals

Abstract

Dislocation interactions with twin boundary (TB) have been well-established in nanotwinned metals. Penta-twins, as an extreme of crystal twinning, are tacitly assumed to be more effective at blocking dislocation motions than conventional single or coplanar nanotwins. However, the mechanism underlying the interactions between dislocations and penta-twins remains largely unclear. Here, by combining in situ transmission electron microscope (TEM) nanomechanical testing and atomistic simulations, we rationalize the fundamental interactions between dislocations and penta-twins in Au nanocrystals. Our results reveal that the interactions between dislocations and penta-twins show some similar behaviors to the ones in the cases of coplanar nanotwins, including dislocation impedance at TBs, cross-slip into the twinning plane and transmission across the TB. In addition, penta-twins also exhibit some unique behaviors during dislocation interactions, including multiple cross-slip, dislocation-induced core dissociation and climb-induced annihilation/absorption at the penta-twin core. These findings enhance our mechanistic understanding of dislocation behaviors in penta-twins, shedding light on the accessible design of high-performance nanomaterials with multi-twinned nanostructures.

In Situ Atomic-Scale Observation of 5-Fold Twin Formation in Nanoscale Crystal under Mechanical Loading

“…Twin boundaries (TBs) with low mobility and boundary energy can be used for tuning the mechanical properties of nanostructured metals, 1 , 2 which have drawn great interest in the field of interface engineering. 3 , 4 As a special twinning morphology, a 5-fold twin (FFT) with five coherent TBs concurrently meeting at their common rotation axis along [110] has been widely observed in metallic nanowires, 5 − 7 nanoparticles, 8 , 9 thin films, 10 and nanocrystalline materials. 11 − 13 Compared to their twin-free counterparts, the nanostructured metals with FFT usually exhibit substantially improved mechanical properties.…”

“…Twin boundaries (TBs) with low mobility and boundary energy can be used for tuning the mechanical properties of nanostructured metals, , which have drawn great interest in the field of interface engineering. , As a special twinning morphology, a 5-fold twin (FFT) with five coherent TBs concurrently meeting at their common rotation axis along [110] has been widely observed in metallic nanowires, − nanoparticles, , thin films, and nanocrystalline materials. − Compared to their twin-free counterparts, the nanostructured metals with FFT usually exhibit substantially improved mechanical properties. − It has been reported that the Young’s modulus of chemically synthesized pentatwinned silver (Ag) nanowires increased from 83 to 176 GPa , and the yield strength increased from 0.71 to 2.64 GPa . Controlling the introduction of FFT into nanostructured metals is of vital importance for fabricating high-performance materials, which requires the knowledge of the underlying formation mechanisms of FFT.…”