Strengthening of Nanosized bcc Cu Precipitate in bcc Fe: A Molecular Dynamics Study

Abstract

The strengthening effect of nanosized Cu precipitates in bcc Fe has been studied by performing molecular dynamics simulations of the interaction between a screw dislocation and a coherent bcc Cu precipitate of 1-4 nm diameter in bcc Fe. The dislocation detachment mechanism changes from shear at a precipitate diameter of 4 and 2.5 nm in the twinning and anti-twinning directions, respectively, due to the coherency loss caused by the screw dislocation assisted martensitic transformation of the precipitate. The screw dislocation detachment mechanism with the larger, transformed precipitates involves annihilation-and-renucleation, or Orowan looping in the twinning vs. anti-twinning direction, respectively. The critical resolved shear stress (CRSS) of the screw dislocation-precipitate interaction increases with increasing precipitate size, and is strongly dependent on the precipitate structure and detachment mechanism. The CRSS is much larger in the anti-twinning direction.

The effect of crystallographic mismatch on the obstacle strength of second phase precipitate particles in dispersion strengthening: bcc Nb particles and nanometric Nb clusters embedded in hcp Zr

“…In this interaction geometry, the slip plane of the particle is parallel to that of the matrix; the obstacle strength of particle is determined solely by shear modulus. Specific examples are a metastable bcc Cu particle embedded in bcc Fe [35,36,50] and an L1 2 -ordered Ni 3 Al particle in fcc Ni [51]. In terms of shear modulus, the former corresponds to a soft obstacle [52], whereas the latter a hard obstacle.…”

Spin polarization gives rise to Cu precipitation in Fe-matrix

“…Copper precipitation plays an important role in the hardening of high-strength low-carbon steels [1][2][3][4] and results in the radiation-embrittlement of operating reactor pressure vessels (RPV) steel. [5][6][7] It is assumed to act as obstacles to dislocation motion.…”

“…Cu precipitation is studied experimentally [1][2][3][5][6][7][8][9][10][11][12][13][14][15] with many characterization techniques, such as 3D atom probes (3D-AP), 12,16,17 high-resolution transmission electron microscopy (HRTEM), 18 small-angle neutron scattering (SANS) 19 and positron annihilation techniques. 9,[20][21][22] Many simulation methods are also used to research Cu precipitation, mainly using first principles [23][24][25][26][27][28][29][30][31][32] at an electronic level, kinetic Monte Carlo (KMC) [33][34][35][36] and molecular dynamics (MD) 3,37 at the atomic level, and also others. [38][39][40] The mechanism of impurity precipitation has been studied intensively.…”

“…Choi et al 29 studied the effect of the nucleated Cu phase on magnetic properties and electronic structures in bcc Fe. Shim et al 3 presented a study on the strengthening effect of nanosized Cu precipitates in bcc Fe by MD simulations. Vincent and Becquart et al 35 wrote a critical review of AKMC simulations about the precipitation in the FeCu system.…”

“…To summarise, many experiments and simulations 12,16,17,[20][21][22]43 focused on the process of Cu precipitation from the Fe matrix; what's more, calculations 3,27,28 were carried out to construct the energy criterion of Cu precipitating from the Fe matrix. There are few articles that attempt to discover the physical essence of Cu precipitation by analyzing the orbital interaction between Fe and Cu at an electronic level.…”