Real-Time Atomic Scale Imaging of Nanostructural Evolution in Aluminum Alloys

Real-Time Atomic Scale Imaging of Nanostructural Evolution in Aluminum Alloys

by | Jul 10, 2017

Dr. Sairam K. Malladi

Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands. Authors | Sairam K. Malladi, Qiang Xu, Marijn A. van Huis, Frans D. Tichelaar, K. Joost Batenburg, Emrah Yücelen, Beata Dubiel, Aleksandra Czyrska-Filemonowicz, and Henny W. Zandbergen. Email | H.W.Zandbergen@tudelft.nl.

Application Real-Time Atomic Scale Imaging of Nanostructural Evolution in Aluminum Alloys
Authors Sairam K. Malladi, Qiang Xu, Marijn A. van Huis, Frans D. Tichelaar, K. Joost Batenburg, Emrah Yücelen, Beata Dubiel, Aleksandra Czyrska-Filemonowicz, and Henny W. Zandbergen.
Journal Nano Lett., 2014, 14 (1), pp 384–389
Sample FIB lamella, Metal
Topic Heat Treatment, Aging, Precipitation
Field Materials Science, Micro Electronics
Techniques HRTEM, EDX mapping
Keywords In situ (S)TEM; precipitation; aluminum alloys
Publication Full Publication Here – DOI 10.1021/nl404565j

Real-Time Atomic Scale Imaging of Nanostructural Evolution in Aluminum Alloys

ABSTRACT: We present a new approach to study the three dimensional alloys during heat treatments such as commonly used for improving overall material properties. It relies on in situ heating in a high-resolution scanning transmission electron microscope (STEM). The approach is demonstrated using a commercial Al alloy AA2024 at 100−240 °C, showing in unparalleled detail where and how precipitates nucleate, grow, or dissolve. The observed size evolution of individual precipitates enables a separation between nucleation and growth phenomena, necessary for the development of refined growth models. We conclude that the in situ heating STEM approach opens a route to a much faster determination of the interplay between local compositions, heat treatments, microstructure, and mechanical properties of new alloys.
FIGURE ABOVE: STEM imaging and EDX maps obtained at each of the intermediate stages of heat-treatment. These maps are obtained with a frame size of 512×512 pixels2 and a frame time of 100 s, averaged over three frames. Notice the Cu redistribution associated with the precipitation at grain boundaries and precipitation in the matrix during the heat-treatment processes. The lath-like nanoprecipitates are enriched with Cu and Mg, suggesting S-phase-type compositions. Throughout the heat-treatment process, the Mn-rich precipitates remained as they are at room temperature.

DENSsolutions Comments:

Most commercial engineering alloys undergo heat treatments to change their intrinsic microstructural properties, such as elemental distribution and precipitate density, to enhance their extrinsic physical properties such as mechanical strength. Despite the key importance of these treatments, studies of the compositional and structural evolution of alloys undergoing heat treatments are fragmented and time consuming as they have been carried out on a set of different samples taken at intermediate stages, which are postmortem data that do not show the evolution of the same area. Achieving in situ TEM observation of heat treatment process at atomic scale enable a full understanding of the relation among process, structure and properties.
The DENSsolutions heating system provides the minimal specimen drift at elevated temperature, allowing a novel in situ method to investigate the aging hardening process that the structural and compositional evolution of alloys can be directly analyzed with time and temperature down to atomic scale.

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Convenient Preparation of High-Quality Specimens for Annealing Experiments in the Transmission Electron Microscope

Convenient Preparation of High-Quality Specimens for Annealing Experiments in the Transmission Electron Microscope

by | Jul 10, 2017

Dr.  Martial Duchamp

Ernst Ruska-Center for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute, Forschungszentrum, Jülich, Germany

Application Convenient Preparation of High-Quality Specimens for Annealing Experiments in the Transmission Electron Microscope
Authors Martial Duchamp, Qiang Xu and Rafal E Dunin-Borkowski.
Journal Microsc. Microanal. 2014, page 1 of 8
Publication Full Publication Here – DOI:10.1017/S1431927614013476

Convenient Preparation of High-Quality Specimens for Annealing Experiments in the Transmission Electron Microscope

ABSTRACT: A procedure based on focused ion beam milling and in situ lift-out is introduced for the preparation of high-quality specimens for in situ annealing experiments in the transmission electron microscope. The procedure allows an electron-transparent lamella to be cleaned directly on a heating chip using a low ion energy and back-side milling in order to minimize redeposition and damage. The approach is illustrated through the preparation of an Al–Mn–Fe complex metallic alloy specimen.

Figure left: Schematic diagram showing the configuration of an FEI dual-beam FIB Helios workstation with the α-flip (AF) holder mounted on the stage. The solid orange lines show the AF and tiltangles. The dotted orange line shows the total tilt angle of thespecimen compared with the horizontal. The inset shows a schematic diagram of a transmission electron microscopic lamella to define the terms used in the text. FIB, focused ion beam.
Figure above: a–i: Scanning electron microscopic images of the different steps used to transfer a 20103 μm lamella from bulk material to a double-tilt heater chip. The tilt angles, positions of the micro-manipulator and Pt needle, and the deposition and etching parameters are given in Table 1. The red arrows in (i) indicate ion-beam-deposited Pt (see text for details).
Figure above: a-c: Focused ion beam (FIB) and (d–f) scanning electron microscopic (SEM) images of the different thinning steps. The tilt angles and milling parameters are given in Table 1: (a) and (d) were acquired after transfer of the lamella onto the chip; (b) and (e) were acquired after milling at 81 pA (step 17 in Table 1); and (c) and (f) after milling at 47 pA (step 18 in Table 1); (g) bright-field; (h) dark-field; and (i) high-angle annular dark-field scanning transmission electron microscopic (STEM) images taken with the STEM detector of the FEI dual-beam Nanolab FIB Helios system. The scale bar for the FIB and SEM images is given in (f), while the scale bar of the STEM images is given in (i). The dot line in (a) shows the edge of the V shape created by the milling in steps 4 and 5 in Table 1, in this way the middle of the lamella can be found when using the back-side milling configuration during the thinning procedure.
Figure left: High-resolution transmission electron microscopic images of the complex metallic alloy specimen attached to a DENSsolutions double-tilt heater chip for annealing experiments. a: Lower side of the lamella in the back-side milling configuration [exposed to the focused ion beam (FIB) during the thinning procedure]. b: Magnified area shown by the red box in (a), ∼50 nm from the specimen edge. The red arrows in (a) show the FIB milling direction.

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