Cross-slip of long dislocations in FCC solid solutions

被引:44
作者
Nohring, Wolfram Georg [1 ,2 ]
Curtin, W. A. [1 ]
机构
[1] Ecole Polytech Fed Lausanne, STI IGM Stn 9, Inst Mech Engn, CH-1015 Lausanne, Switzerland
[2] Univ Freiburg, Dept Microsyst Engn, Georges Kohler Allee 103, DE-79110 Freiburg, Germany
基金
欧洲研究理事会;
关键词
Screw dislocation; Cross-slip; Face-centered cubic crystals; Solid solution; Stochastic model; ATOMISTIC SIMULATIONS; HYDROGEN EMBRITTLEMENT; SCREW DISLOCATIONS; MODEL; INTERSECTIONS; DEFORMATION; ELEMENTS; STRESS; ENERGY; ANNIHILATION;
D O I
10.1016/j.actamat.2018.05.027
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Cross-slip of screw dislocations is a dislocation process involved in dislocation structuring, work hardening, and fatigue. Cross-slip nucleation in FCC solid solution alloys has recently been shown to be strongly influenced by local fluctuations in spatial arrangement of solutes, leading to a statistical distribution of cross-slip nucleation barriers. For cross-slip to be effective macroscopically, however, small cross-slip nuclei (similar to 40b) must expand across the entire length of typical dislocation segments (10(2)-10(3)b). Here, a model is developed to compute the relevant activation energy distribution for cross-slip in a random FCC alloy over arbitrary lengths and under non-zero Escaig and Schmid stresses. The model considers cross-slip as a random walk of successive flips of adjacent 1b segments, with each flip having an energy consisting of a deterministic contribution due to constriction formation and stress effects, plus a stochastic contribution. The corresponding distribution is computed analytically from solute dislocation and solute-solute binding energies. At zero stress, the probability of high activation energies increases with dislocation length. However, at stresses of just a few MPa, these barriers are eliminated and lower barriers are dominant. For increasing segment length, the effective energy barrier decreases according to a weak-link scaling relationship and good analytic predictions can be made using only known material properties. Overall, these results show that the effective cross-slip barrier in a random alloy is significantly lower than estimates based on average elastic and stacking fault properties of the alloy. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
引用
收藏
页码:95 / 117
页数:23
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