Influence of grain boundary characteristics on thermal stability in nanotwinned copper

Abstract

High density grain boundaries provide high strength, but may introduce undesirable features, such as high Fermi levels and instability. We investigated the kinetics of recovery and recrystallization of Cu that was manufactured to include both nanotwins (NT) and high-angle columnar boundaries. We used the isothermal Johnson-Mehl-Avrami-Kolmogorov (JMAK) model to estimate activation energy values for recovery and recrystallization and compared those to values derived using the non-isothermal Kissinger equation. The JMAK model hinges on an exponent that expresses the growth mechanism of a material. The exponent for this Cu was close to 0.5, indicating low-dimensional microstructure evolution, which is associated with anisotropic twin coarsening, heterogeneous recrystallization, and high stability. Since this Cu was of high purity, there was a negligible impurity-drag-effect on boundaries. The twin coarsening and heterogeneous recrystallization resulted from migration of high-angle columnar boundaries with their triple junctions in one direction, assisted by the presence of high concentration vacancies at boundaries. Analyses performed by electron energy loss spectroscopy of atomic columns at twin boundaries (TBs) and in the interior showed similar plasma peak shapes and L3 edge positions. This implies that values for conductivity and Fermi level are equal for atoms at TBs and in the interior.

Modeling of grain growth under fully anisotropic grain boundary energy

“…In [52], it is shown that twin migration enhances plastic deformation in Al. The thermal grain structure stability in nanocrystalline Cu is related to the presence of twin boundaries in [53]. In passing, it can be noted that not only the energy but also the mobility of CTBs and ICBs depend on the local crystal structure, see [54].…”

The versatility of the dynamic hydrogen bubble template derived copper foam on the emerging energy applications: progress and future prospects

“…[110][111][112] In earlier studies, copper foil was usually used as the active material, as well as supporting electrodes, exploiting metastable grain boundaries. 113,114 However, the atness of the traditional foil current collectors reduces the physical and electrical contact area available for (1) adhesion of the electrode materials to and (2) electron transfer with the electrodes. 115 Inspired by the fact that maximum surface area and active sites will easily be accessible to the electrolyte ions on the metastable grain boundaries of a porous structure, researchers later focussed on the utilization of Cuf for electrochemical reactions for better control of reaction pathways and mass transport.…”

Stress Relaxation and Grain Growth Behaviors of (111)-Preferred Nanotwinned Copper during Annealing

“…No obvious change in the grain orientation was found when electroplated with a low current density (4 or 8 ASD). This indicates a great thermal stability of such nt-Cu films because their coherent twin boundaries are strongly stable at elevated temperatures [ 55 , 56 , 57 ]. In addition, twins of Cu can alter their surface structure and grain boundary leading to the stability of the twin boundaries and surface [ 58 , 59 ].…”