Investigation of geometrically necessary dislocation structures in compressed Cu micropillars by 3-dimensional HR-EBSD

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

卷:770

Article

Kalacska, Szilvia^1,2  Dankhazi, Zoltan¹  Zilahi, Gyula¹  Maeder, Xavier²  Michler, Johann²  Ispanovity, Peter Dusan¹  Groma, Istvan¹ 

[1] Eotvos Lorand Univ, Dept Mat Phys, Pazmany Peter Setany 1-A, H-1117 Budapest, Hungary

[2] Empa, Swiss Fed Labs Mat Sci & Technol, Lab Mech Mat & Nanostruct, Feuerwerkerstr 39, CH-3602 Thun, Switzerland

关键词: Micromechanics;    Stress/strain measurements;    Electron microscopy;    Characterization;    Plasticity;   

DOI  :  10.1016/j.msea.2019.138499

来源: Elsevier

【 摘 要 】

Mechanical testing of micropillars Is a field that involves new physics, as the behaviour of materials is nondeterministic at this scale. To better understand their deformation mechanisms we applied 3-dimensional high angular resolution electron backscatter diffraction (3D HR-EBSD) to reveal the dislocation distribution in deformed single crystal copper micropillars. Identical micropillars (6 mu m x 6 mu m x18 mu m in size) were fabricated by focused ion beam (FIB) and compressed at room temperature. The deformation process was stopped at different strain levels (approximate to 1%, 4% and 10%) to study the evolution of geometrically necessary dislocations (GNDs). Serial slicing with FIB and consecutive HR-EBSD mapping on the (100) side was used to create and compare 3-dimensional maps of the deformed volumes. Average GND densities were calculated for each deformation step. Total dislocation density calculation based on X-ray synchrotron measurements were conducted on the 4% pillar to compare dislocation densities determined by the two complementary methods. Scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) images were captured on the 10% pillar to visualize the actual dislocation structure. With the 3D HR-EBSD technique we have studied the geometrically necessary dislocations evolving during the deformation of micropillars. An intermediate behaviour was found at the studied sample size between bulk and nanoscale plasticity: A well-developed dislocation cell structure built up upon deformation but with significantly lower GND density than in bulk. This explains the simultaneous observation of strain hardening and size effect at this scale.

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