Possible origin of the discrepancy in Peierls stresses of fcc metals: First-principles simulations of dislocation mobility in aluminum

Dislocation motion governs the strength and ductility of metals, and the Peierls stress ([sigma]p) quantifies dislocation mobility. [sigma]p measurements carry substantial uncertainty in face-centered cubic (fcc) metals, and [sigma]p values can differ by up to two orders of magnitude. We perform fir...

Full description

Saved in:
Bibliographic Details
Published in:Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2013-08, Vol.88 (6), Article 064106
Main Authors: Shin, Ilgyou, Carter, Emily A.
Format: Article
Language:English
Subjects:
Aluminum
Condensed matter
Dislocation mobility
Dislocations
FCC metals
Mathematical analysis
Screw dislocations
Simulation
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Dislocation motion governs the strength and ductility of metals, and the Peierls stress ([sigma]p) quantifies dislocation mobility. [sigma]p measurements carry substantial uncertainty in face-centered cubic (fcc) metals, and [sigma]p values can differ by up to two orders of magnitude. We perform first-principles simulations based on orbital-free density functional theory (OFDFT) to calculate the most accurate currently possible [sigma]p for the motion of [1/2][left angle bracket]110[right angle bracket] {111} dislocations in fcc Al. We predict the [sigma]ps of screw and edge dislocations (dissociated in their equilibrium state) to be 1.9 x 10 super(-4)G and 4.9 x 10 super(-5)G, respectively (G is the shear modulus). These values fall within the range of measurements from mechanical deformation tests (10 super(-4)-10 super(-5)G). OFDFT also finds a new metastable structure for a screw dislocation not seen in earlier simulations, in which a dislocation core on the glide plane does not dissociate into partials. The corresponding [sigma]p for this undissociated dislocation is predicted to be 1.1 x 10 super(-2)G, which agrees with typical Bordoni peak measurements (10 super(-2)-10 super(-3)G). The calculated [sigma]ps for dissociated and undissociated screw dislocations differ by two orders of magnitude. The presence of undissociated, as well as dissociated, screw dislocations may resolve the decades-long mystery in fcc metals regarding the two orders of magnitude discrepancy in [sigma]p measurements.
ISSN:1098-0121
1550-235X
DOI:10.1103/PhysRevB.88.064106