Structure and stability of Σ3 grain boundaries in face centered cubic metals

Abstract

AE3 grain boundaries form as a result of either growth twinning or deformation twinning in face centered cubic (fcc) metals and play a crucial role in determining the mechanical and electrical properties and microstructural stability. We studied the structure and stability of AE3 grain boundaries (GBs) in fcc metals by using topological analysis and atomistic simulations. Atomistic simulations were performed for Cu and Al with empirical interatomic potentials to reveal the influence of stacking fault energy on the morphology of the twinned grains. Three sets of tilt AE3 GBs were studied with respect to the tilt axis parallel to h111i, h112i, and h110i, respectively. We showed that AE3{111} and AE3{112} GBs are thermodynamically stable and the others will dissociate into terraced interfaces regardless of the stacking fault energy. The morphology of the nanotwinned grains in Cu is predicted from the above analysis and found to match with experiments.

The dual role of coherent twin boundaries in hydrogen embrittlement

“…Among low-S GBs, we call particular attention to S3 CTBs because they are often thought to improve mechanical strength and resistance to stress corrosion cracking in metal alloys 16 . These qualities stem from the especially low energy of S3 CTBs, I n t e r g r a n u l a r T r a n s g r a n u la r which is due to perfect, atom-to-atom registry between adjoining crystals at such boundaries 17 . As shown in Fig.…”

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

“…The twinned structure can change the energy and the mobility of a mobile interface. It is suggested that the slowest growing grains could lead to the largest fraction of TBs, in that the new twin orientations presumably provide the excess boundary energy required to continue growth [46,75]. Fewer twins generally nucleate at a higher GB migration rate, whereas more twins are found at lower growth rate in pure (NC) metals, since the twinning process is of minor importance as an energy reduction mechanism when reduction in GB area, i.e., fast GG, is strongly operative [50].…”

“…For example, Olmsted et al [83] investigated the GG in Ni through simulations of boundary mobility and misorientation type and showed that the lowest energy boundary is the coherent TB Σ3 601 (111), spanning from 0.06 J m À 2 (coherent TBs) to 1.0 J m À 2 . Although the coherent TB is a Σ3 boundary, it is worth noting only 41 types of Σ3 boundaries were studied in a previous work, all of which have the same misorientation between grains but different inclination planes, therefore exhibiting different mobilities [75,[84][85][86]. GB energy can provide a great driving force for grain coarsening and contribute to which grains coarsen at a faster rate than their neighbors.…”

Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts

“…Experimental studies have uncovered that NT metals have ultrahigh strength/hardness, 24,25,38,[48][49][50] good ductility 25,51,52 and great strain hardening. 25,51,53 Corresponding to these experimental outcomes, a large quantity of theoretical studies are available, such as the intrinsic size effects and plastic anisotropy, the stability of NT structures, 54,55 the effect of surface stress 56,57 and NT structures in CG system on the mechanical properties of metals. [58][59][60][61] Moreover, the electrical conductivity of NT bulk metals is similar to the conventional CG counterpart but much higher than NC metals.…”