The transformation of edge dislocation dipoles in aluminium

The formation of stacking fault tetrahedra in Al and CuII. SFT growth by successive absorption of vacancies generated by dipole annihilation

“…5a and b) sharing a face with the initial 28-SFT similar to the configurations sketched in Fig. 8a and b and 10a and b of Wang et al Part III [40]. It is noted that small sized SFTs do not form by the ledge mechanism commonly admitted in the dislocation-equivalent description of SFT growth [17,19].…”

“…In Part I [40], devoted to the segregation stages that follow dipole annihilation, it is shown that clustering up to trivacancies greatly enhances reaction rates. At this stage the number of configurations adopted by point defect clusters approaching an SFT, be it perfect or not, makes a systematic coverage of SFT growth by vacancy absorption beyond the reach of MD simulations, thus imposing simplifying choices, discussed hereafter.…”

“…In continuation of previous MD investigations of the transformation of edge dislocation dipoles [40][41][42], the stage of SFT growth is studied in detail with the help of static energy calculations and MD aging, as well as elasticity calculations.…”

“…The nudge elastic band (NEB) technique was employed to evaluate the barriers for vacancy migration on the SFT face. MD aging was mostly performed at 900 and 1300 K for both Al and Cu [40]. Since perfect SFTs can grow from a Frank loop only if the latter is perfectly triangular, this loop must contain specific numbers of vacancies (N) or, equivalently, of h1 1 0i vacancy rows (n), such that N = n (1 + n)/2.…”

“…Such complexity is rather well illustrated by Fig. 1 in Wang et al Part I [40], where SFT growth consumes the vacancy clusters generated by dislocation annihilation, a scenario used in what follows.…”