Cleavages along {110} in bcc iron emit dislocations from the curved crack fronts

Suzudo, Tomoaki; Ebihara, Kenichi; Tsuru, Tomohito; Mori, Hideki*

Scientific Reports (Internet), 12, p.19701_1 - 19701_10, 2022/11

https://doi.org/10.1038/s41598-022-24357-5

Body-centered-cubic (bcc) transition metals, such as -Fe and W, cleave along the {100} plane, even though the surface energy is the lowest along the {110} plane. To unravel the mechanism of this odd response, large-scale atomistic simulations of curved cleavage cracks of -Fe were conducted in association with stress intensity factor analyses of straight crack fronts using an interatomic potential created by an artificial neural network technique. The study provides novel findings: Dislocations are emitted from the crack fronts along the {110} cleavage plane, and this phenomenon explains why the {100} plane can be the cleavage plane. However, the simple straight crack-front analyses did not yield the same conclusion. It is suggested that atomistic modeling, at sufficiently large scales to capture the inherent complexities of materials using highly accurate potentials, is necessary to correctly predict the mechanical strength. The method adopted in this study is generally applicable to the cleavage problem of bcc transition metals and alloys.

Analyzing the cross slip motion of screw dislocations at finite temperatures in body-centered-cubic metals; Molecular statics and dynamics studies

Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*

Modelling and Simulation in Materials Science and Engineering, 27(6), p.064001_1 - 064001_15, 2019/08

https://doi.org/10.1088/1361-651X/ab235e

Plasticity of body-centered-cubic (BCC) metals at low temperatures is determined by screw dislocation kinetics. Because the core of screw dislocation in these metals has non-planar structure, its motion is complex and unpredictable. For example, although density functional theory (DFT) predicts slip on a { 110 } plane, the actual slip plane at elevated temperatures departs from the prediction, its mechanism having been a mystery for decades. Here we conduct a series of molecular dynamics simulations to track the screw dislocation motion and successfully reproduced the transition of the slip plane. We then devised an algorithm to scrutinize the activation of dislocation jump over the Peierls barrier and discovered the possible origin of this unexpected phenomenon, i.e., a large fluctuation leads to the kink-pair nucleation for the cross-slip jump without transition of dislocation core structure.

Computer Simulations of Knock-on Processes in Crystals

*; ;

JAERI-M 87-026, 25 Pages, 1987/02

JAERI-M-87-026.pdf:0.67MB

no abstracts in English

Simulation of slip plane transition from {110} to {112} of body-centered-cubic metals

Suzudo, Tomoaki; Fukumoto, Kenichi*

no journal, , 

Body-centered cubic (BCC) metals are applied as structural materials to many components of nuclear reactors, and their thermal and mechanical integrity are of great importance. Much of the deformation of BCC metals at low temperatures is due to the movement of screw dislocations. The motion of screw dislocations in BCC metals is known to be complex. In this research, we succeeded in reproducing the transition of the slip plane as the temperature rise observed in the experiment for the first time using the latest molecular dynamics modeling method. Next, we devised an algorithm to analyze dislocation jumps over the Peierls barrier with high resolution, and showed that the cause of this slip-plane transition phenomenon is likely thermal fluctuation of lattice.