Atom probe field ion microscopy Research Papers (original) (raw)

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- by and +1
- •
- Surface Science, Corrosion Science, Science, Atom probe field ion microscopy

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Invited lecture, German-Chinese High-level Workshop on “Microstructure-driven Design and Performance of Advanced Metals” held 12-16. April 2013 in the Institute of Metals Research (IMR) of the Chinese Academy of Science (CAS), Shenyang,... more

- by Alfred Cerezo
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- Materials Engineering, Mechanical Engineering, Electron Microscopy, Kinetics

In atom probe tomography (APT), multiple events can arise as a consequence of e.g. correlated field evaporation and molecular ion dissociation. They represent challenging cases for single-particle detectors and can cause compositional as well as spatial inaccuracies. Here, two state-of-the-art atom probe microscopes (Cameca LEAP 50 0 0 XS and 50 0 0 XR) were used to investigate cemented tungsten carbide, which exhibits high amounts of multiple events. By advanced data analysis methods, the natural character of the multiple events, as well as the performance of the APT detectors, are assessed. Accordingly, possible signal loss mechanisms are discussed.

Carbon partitioning between ferritic and austenitic phases is essential for austenite stabilization in the most advanced steels such as those produced by the quenching and partitioning (Q&P) process. The atomistic analysis of the carbon partitioning in Q&P alloys is, however, difficult owing to the simultaneous occurrence of bainite transformation, which can also contribute to carbon enrichment into remaining austenite and hence overlap with the carbon partitioning from martensite into austenite. Therefore, we provide here a direct atomic-scale evidence of carbon partitioning from martensite into austenite without the presence of bainite transformation. Carbon partitioning is investigated by means of atom probe tomography and correlative transmission electron microscopy. A model steel (Fe–0.59 wt.% C (2.7 at.% C)–2.0 wt.% Si–2.9 wt.% Mn) with martensite finish temperature below room temperature was designed and used in order to clearly separate the carbon partitioning between martensite and austenite from the bainite transformation. The steel was austenitized at 900 C, then water-quenched and tempered at 400 C. Approximately 8 vol.% retained austenite existed in the as-quenched state. We confirmed by X-ray diffraction and dilatometry that austenite decomposition via bainite transformation did not
occur during tempering. No carbon enrichment in austenite was observed in the as-quenched specimen. On the other hand, clear carbon enrichment in austenite was observed in the 400 C tempered specimens with a carbon concentration inside the austenite of 5–8 at.%. The results hence quantitatively revealed carbon partitioning from martensite to austenite, excluding bainite transformation during the Q&P heat treatment.

Field ion microscopy (FIM) allows to image individual surface atoms by exploiting the effect of an intense electric field. Widespread use of atomic resolution imaging by FIM has been hampered by a lack of efficient image processing/data extraction tools. Recent advances in imaging and data mining techniques have renewed the interest in using FIM in conjunction with automated detection of atoms and lattice defects for materials characterization. After a brief overview of existing routines, we review the use of machine learning (ML) approaches for data extraction with the aim to catalyze new data-driven insights into high electrical field physics. Apart from exploring various supervised and unsupervised ML algorithms in this context, we also employ advanced image processing routines for data extraction from large sets of FIM images. The outcomes and limitations of such routines are discussed, and we conclude with the possible application of energy minimization schemes to the extracted point clouds as a way of improving the spatial resolution of FIM.

- by Dierk Raabe
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- Materials Science, Machine Learning, Data Mining, Metallurgy

Atom probe tomography (APT) is rising in influence across many parts of materials science and engineering thanks to its unique combination of highly sensitive composition measurement and three-dimensional microstructural characterization. In this invited article, we have selected a few recent applications that showcase the unique capacity of APT to measure the local composition at structural defects. Whether we consider dislocations, stacking faults, or grain boundary, the detailed compositional measurements tend to indicate specific partitioning behaviors for the different solutes in both complex engineering and model alloys we investigated.

- by Dierk Raabe
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- Electron Microscopy, Segregation, Metallurgy, Atom probe field ion microscopy

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- by K. Hoummada and +1
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- Materials Engineering, Mechanical Engineering, Atom probe field ion microscopy, Transition-Metal Oxides

Atom-probe field-ion microscopy (APFIM) is used to study partitioning of the alloying elements between the ? (FCC) and ?' (L12) phases and their segregation behavior at ?/?' interfaces of a René N6 nickel-based superalloy. The atomic-scale resolution and real space reconstruction capability for elemental chemical mapping makes three-dimensional atom-probe microscopy especially suitable for subnanoscale investigations of complex multicomponent superalloys. Concentration

- by David N Seidman
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- Engineering, Atom probe field ion microscopy, Nickel, CHEMICAL SCIENCES
- by Stan David and +1
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- Materials Engineering, Mechanical Engineering, Atom probe field ion microscopy, Transmission Electron Microscopy
- by Alfred Cerezo
- •
- Materials Engineering, Mechanical Engineering, Electron Microscopy, Kinetics
- by Aldo Romero
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- Surface Science, Corrosion Science, Science, Atom probe field ion microscopy

... an average width of 250nm (3), grouped together in packets mainly with low angle boundaries between each lath, although a minority are separated by high angle grain boundaries ... An anticlockwise spiral starts on the right hand side... more

The laser assisted atom probe has been proposed as a metrology tool for next generation semiconductor technologies requiring subnanometer depth resolution. In order to support its routine application, we carried out a quantitative... more

Increasing the strength of metallic alloys while maintaining formability is an interesting
challenge for enabling new generations of lightweight structures and technologies. In this paper,
we engineer aluminium alloys to contain a hierarchy of nanostructures and possess mechanical
properties that expand known performance boundaries — an aerospace-grade 7075 alloy
exhibits a yield strength and uniform elongation approaching 1 GPa and 5 % , respectively. The
nanostructural architecture was observed using novel high-resolution microscopy techniques
and comprises a solid solution, free of precipitation, featuring (i) a high density of dislocations,
(ii) subnanometre intragranular solute clusters, (iii) two geometries of nanometre-scale
intergranular solute structures and (iv) grain sizes tens of nanometres in diameter. Our results
demonstrate that this novel architecture offers a design pathway towards a new generation of
super-strong materials with new regimes of property-performance space.