Abstract

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.

Highlights

  • Field-ion-based techniques were initially developed for studying surfaces[1,2]: The field ion microscope (FIM) reveals the structure of a material with atomic-scale resolution,[3] at least in some parts of the image, while the implementation of a time-of-flight spectrometer onto a FIM, which is the atom probe, targeted the elemental identification of atoms images at the surface.[4]

  • Limited detection efficiency along with aberrations in the trajectories of the ions emitted from the surface dramatically affects the spatial resolution of APT20,25,26 and prevent the instrument to attain true atomic resolution; it reveals precise compositional information in three-dimensions that FIM could not provide

  • With Atom probe tomography (APT)’s limited capacity for detecting lattice defects, a strategy has sometimes been pursued to use a foreign atom with a high tendency for segregation to mark defects for analysis

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Summary

INTRODUCTION

Field-ion-based techniques were initially developed for studying surfaces[1,2]: The field ion microscope (FIM) reveals the structure of a material with atomic-scale resolution,[3] at least in some parts of the image, while the implementation of a time-of-flight spectrometer onto a FIM, which is the atom probe, targeted the elemental identification of atoms images at the surface.[4]. APT is primarily a massspectrometry technique, albeit with an unparalleled spatial resolution.[20,21,22,23,24] Limited detection efficiency along with aberrations in the trajectories of the ions emitted from the surface dramatically affects the spatial resolution of APT20,25,26 and prevent the instrument to attain true atomic resolution; it reveals precise compositional information in three-dimensions that FIM could not provide. APT data, still often contains partial structural information that can be exploited to complement the microstructural and compositional information provided by the technique.[27,28] Significant effort arose in the past decade to retrieve, extract, and make use of this structural information when available, to bring more insights into the complex structure-defects-composition interplay that, in combination, rules the physical properties of materials.[29,30,31,32,33]. Some of the most seminal work in the APT community was focused on these aspects, in intermetallics,[34,35] steel,[36] superalloys,[37,38] and in semiconductors.[39,40,41,42] In this invited feature article, we will showcase a few recent applications of APT from within our group at the Max-Planck-Institut für Eisenforschung that aimed to measure the local composition at specific structural defects, to explain fundamental aspects of phase formation and transformation or deformation mechanisms

EXPERIMENTAL
Al-alloys
Line defects near oxidized carbides in Ni-based superalloys
Segregation to stacking faults
Segregation in CIGS
Phase nucleation at crystalline defects
Heterogeneous nucleation of hydrides in titanium
SUMMARY
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