Shear stress- and line length-dependent screw dislocation cross-slip in FCC Ni

Date
2017-01-01
Authors
Xiong, Liming
Xiong, Liming
Chen, Youping
McDowell, David L.
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier Ltd.
Altmetrics
Authors
Xiong, Liming
Person
Associate Professor
Research Projects
Organizational Units
Aerospace Engineering
Organizational Unit
Journal Issue
Series
Department
Aerospace Engineering
Abstract
Screw dislocation cross-slip is important in dynamic recovery of deformed metals. A mobile screw dislocation segment can cross slip to annihilate an immobile screw dislocation segment with opposite Burgers vector, leaving excess dislocations of one kind in a crystal. Previous studies have found that the cross-slip process depends on both the local stress state and dislocation line length, yet a quantitative study of the combined effects of these two factors has not been conducted. In this work, we employ both dynamic concurrent atomistic-continuum (CAC) [L. Xiong, G. Tucker, D.L. McDowell, Y. Chen, J. Mech. Phys. Solids 59 (2011) 160–177] and molecular dynamics simulations to explore the shear stress- and line length-dependent screw dislocation cross-slip in face-centered cubic Ni. It is demonstrated that the CAC approach can accurately describe the 3-D cross-slip process at a significantly reduced computational cost, as a complement to other numerical methods. In particular, we show that the Fleischer (FL) [R.L. Fleischer, Acta Metall. 7 (1959) 134–135] type cross-slip, in which a stair-rod dislocation is involved, can be simulated in the coarse-grained domain. Our simulations show that as the applied shear stress increases, the cross-slip mechanism changes from the Friedel-Escaig (FE) [B. Escaig, J. Phys. 29 (1968) 225–239] type to the FL type. In addition, the critical shear stress for both cross-slip mechanisms depends on the dislocation line length. Moreover, the cross-slip of a screw dislocation with a length of 6.47 nm analyzed using periodic boundary conditions occurs via only the FL mechanism, whereas a longer dislocation with length of 12.94 nm can cross-slip via either the FE or FL process in Ni subject to different shear stresses.
Comments
This is a manuscript of an article published as Xu, Shuozhi, Liming Xiong, Youping Chen, and David L. McDowell. "Shear stress-and line length-dependent screw dislocation cross-slip in FCC Ni." Acta Materialia 122 (2017): 412-419. DOI: 10.1016/j.actamat.2016.10.005. Copyright 2016 Acta Materialia Inc. Posted with permission.
Description
Keywords
DegreeDisciplines::Engineering::Aerospace Engineering::Structures and Materials
Citation
DOI
Collections