Stacking fault tetrahedra in metals

Formation and growth of stacking fault tetrahedra in Ni via vacancy aggregation mechanism

“…[5] However, there remains a speculation about whether the nucleation of SFT (in melt-quench or irradiation) indeed requires condensation of vacancies into loops followed by their transformation into SFT, or if it could form by simple agglomeration of vacancies. [2,[6][7][8][9][10] De Jong and Koehler [2] initially postulated the vacancy-tetrahedron as a nucleation center for SFT, and later some experimental and theoretical studies indicated the possibility of this mechanism. [10][11][12] However, due to the lack of direct atomistic observation under experiments, and the absence of MD simulations that capture diffusion and clustering of vacancies to form SFT, the operation of such a mechanism has not yet been fully ascertained.…”

“…[10][11][12] However, due to the lack of direct atomistic observation under experiments, and the absence of MD simulations that capture diffusion and clustering of vacancies to form SFT, the operation of such a mechanism has not yet been fully ascertained. [6,7] In addition, while growth of SFT has been largely perceived to occur by accumulation of vacancies on SFT, and atomistic static calculations have been previously performed in this regard to understand the energy landscape and the vacancy-SFT interactions, [13,14] MD simulations have not yet dynamically captured the diffusion-based SFT growth to clearly show the operation of a vacancy aggregation mechanism. Furthermore, while previous studies have shown direct formation of SFT during a collision-cascade event, [15,16] illustrating the SFT formation by the vacancy aggregation mechanism will indicate that they can also form much after the cascade event has occurred, or under non-cascade irradiation conditions (e.g., electrons, light ions and thermal neutrons) by the aggregation of irradiation-induced free vacancies.…”

Atomistic Simulation of the Interaction Between Point Defects and Twin Boundary

“…The coordinate axis for the crystal and twinned regions are indicated in Figure (a). The SFT was chosen for study because it is an important type of vacancy cluster in various irradiated face‐centered cubic (fcc) metals . Following the previous method, the initial SFT structure was created from an equilateral triangle vacancy plate on the basis of the Silcox–Hirsch mechanism.…”

The formation and destruction of stacking fault tetrahedron in fcc metals: A molecular dynamics study

“…The formation mechanisms of SFT has been studied in many of the previous experimental and numerical simulations [3][4][5][6][7][8], including (i) the diffusion and clustering of point defects; (ii) various mechanisms involving the glide and cross slip of dislocations, and (iii) the merging of glide elements followed by growth [2]. A high density of nanometer-sized SFTs was commonly found in metals during rapid quenching [6,9,10], under severe plastic deformation [11,12], or subjected to radiation damage [13,14].…”

“…Also, it was found that the compressive stress can unzip the perfect SFT to a truncated one, and can facilitate the destruction of SFT by transforming the faulted Frank loop to the unfaulted full dislocation loop. We provided the atomic details of how the unfaulting occurs using molecular dynamics method.Stacking fault tetrahedron (SFT) is the most general type of vacancy clustered defects in face-centered cubic (fcc) metals, due to its favorable structure that contains close-packed planes [1,2]. The formation mechanisms of SFT has been studied in many of the previous experimental and numerical simulations [3][4][5][6][7][8], including (i) the diffusion and clustering of point defects; (ii) various mechanisms involving the glide and cross slip of dislocations, and (iii) the merging of glide elements followed by growth [2].…”