Mobility law of dislocations with several character angles and temperatures in FCC aluminum

Abstract

We study the mobility law of dislocations in aluminum as an important building block for the development of a multiscale method that couples an atomistic model with discrete dislocation dynamics in 3d (e.g., CADD3d). Straight dislocations of arbitrary character angles are modeled with classical molecular dynamics at several temperatures. The obtained mobility results are analyzed and validated by comparisons to theoretical models. A critical velocity parameter identified by the analytic models is correlated to the material dispersive nature. We revisit the interpretation of this constant by considering character angles that were not studied previously. Finally, the obtained mobility law is implemented and employed in the discrete dislocation dynamics simulation of a dislocation loop. Our results highlight the importance of including several angles when constructing the mobility law to produce consistent results.

Discrete dislocation dynamics simulations of dislocation-θ′ precipitate interaction in Al-Cu alloys

“…The drag coefficient vector, B, that characterizes the dislocation mobility has been recently determined in Al by Cho et al (2017). They carried out molecular dynamics simulations of straight dislocation segments with different character and determined B as a function of temperature in the regime in which the dislocation mobility is controlled by the viscous friction force arising from phonon damping.…”

“…θ = 0 • stands for pure screw dislocation and θ = 90 • for pure edge dislocation. The solid symbols stand for moecular dynamics simulation inCho et al (2017), while the solid line corresponds to eq. (19).…”

Multiscale modelling of precipitation hardening in Al–Cu alloys: Dislocation dynamics simulations and experimental validation

“…It should be finally noted that that all the parameters that determine the interaction between the Al matrix and the precipitates were obtained from atomistic simulations or independent experimental observations and the results are free from adjustable parameters. In particular, lattice and elastic constants of the matrix and the precipitate were computed from DFT simulations [22], dislocation mobility and cross-slip parameters were obtained from MD simulations [36,39] and the solid solution contribution to the CRSS in addition to the details of the precipitate size, shape and volume fraction were taken from experimental observations [23]. Moreover, DDD simulations in combination with multiscale modelling strategies to simulate precipitate nucleation and growth during thermal treatments [52] can be used to optimize precipitate hardening of metallic alloys or design new alloys improved mechanical properties [53].…”

Analytic model of the remobilization of pinned glide dislocations: Including dislocation drag from phonon wind

“…[22] which relied on experimental shock data for their model parameters in order to make predictions in the high stress regime. More recent approaches [4,[34][35][36][37][38][39][40] aim at providing a more accurate description of the high stress regime based on the microscopic physics of dislocation mobility. However, one of the main obstacles encountered by these "microscopic" strength models has been the uncertainty as to how B behaves at high velocities, temperatures, and pressures.…”

“…(see e.g. [40][41][42][43]) to B ∼ √ v above some threshold velocity [4,38,39], to "relativistic factors" B ∼ 1/(1 − v 2 /v 2 crit ) m with a limiting (critical) velocity v crit and a range of powers 1/2 ≤ m ≤ 4 [34][35][36][37]. In these references, the pressure and density dependence of B is largely ignored (except for the "relativistic factors" whose limiting velocity depends on the shear modulus).…”