Dislocation structures and the role of grain boundaries in cyclically deformed Ni micropillars

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:769

Article

Samaee, Vahid¹  Sandfeld, Stefan²  Idrissi, Hosni^1,3  Groten, Jonas⁵  Pardoen, Thomas³  Schwaiger, Ruth⁴  Schryvers, Dominique¹ 

[1] Univ Antwerp, Dept Phys, Electron Microscopy Mat Sci EMAT, Groenenborgerlaan 171, B-2020 Antwerp, Belgium

[2] TU Bergakad Freiberg TUBAF, Inst Mech & Fluid Dynam, Micromech Mat Modelling MiMM, Lampadiusstr 4, D-09596 Freiberg, Germany

[3] UCLouvain, Inst Mech Mat & Civil Engn, B-1348 Louvain La Neuve, Belgium

[4] Karlsruhe Inst Technol, Inst Appl Mat, Hermann von Helmholtz Pl 1, D-76344 Eggenstein Leopoldshafen, Germany

[5] Joanneum Res, Graz, Austria

关键词: Transmission electron microscopy (TEM);    Dislocations;    Cell structures;    Simulation;    Computational analysis;   

DOI  :  10.1016/j.msea.2019.138295

来源: Elsevier

【 摘 要 】

Transmission electron microscopy and finite element-based dislocation simulations were combined to study the development of dislocation microstructures after cyclic deformation of single crystal and bicrystal Ni micropillars oriented for multi-slip. A direct correlation between large accumulation of plastic strain and the presence of dislocation cell walls in the single crystal micropillars was observed, while the presence of the grain boundary hampered the formation of wall-like structures in agreement with a smaller accumulated plastic strain. Automated crystallographic orientation and nanostrain mapping using transmission electron microscopy revealed the presence of lattice heterogeneities associated to the cell walls including long range elastic strain fields. By combining the nanostrain mapping with an inverse modelling approach, information about dislocation density, line orientation and Burgers vector direction was derived, which is not accessible otherwise in such dense dislocation structures. Simulations showed that the image forces associated with the grain boundary in this specific bicrystal configuration have only a minor influence on dislocation behavior. Thus, the reduced occurrence of mature cell walls in the bicrystal can be attributed to the available volume, which is too small to accommodate cell structures.

【 授权许可】

Free