The first direct observation of hydrogen trapping sites in TiC precipitation-hardening steel through atom probe tomography

2010 ◽  
Vol 63 (3) ◽  
pp. 261-264 ◽  
Author(s):  
Jun Takahashi ◽  
Kazuto Kawakami ◽  
Yukiko Kobayashi ◽  
Toshimi Tarui
Keyword(s):  
Direct Observation ◽  
Atom Probe Tomography ◽  
Precipitation Hardening ◽  
Atom Probe ◽  
Hydrogen Trapping ◽  
Trapping Sites

Dislocation nucleation at nanoscale fluid inclusions: Direct observation from atom probe tomography data of naturally deformed pyrite

2020 ◽  
Author(s):  
Renelle Dubosq ◽  
Anna Rogowitz ◽  
Kevin Schweinar ◽  
Baptiste Gault ◽  
David Schneider
Keyword(s):  
Direct Observation ◽  
Fluid Inclusions ◽  
Atom Probe Tomography ◽  
Stress Gradient ◽  
Atom Probe ◽  
Dislocation Nucleation ◽  
Crystal Defects ◽  
Trace Element Mobility ◽  
Gold Silver ◽  
Material Sciences

<p>In recent years, increasing developments in microscopy and microanalysis have allowed for the direct observation of nanoscale crystalline defects (i.e. dislocations). These defects are particularly important in naturally deformed materials yet this avenue of research remains understudied within the Earth Sciences. Dislocations can now be documented through the use of new and innovative structural and chemical analytical techniques such as electron channeling contrast imaging (ECCI), transmission electron microscopy, and atom probe tomography (APT). The presence and migration of dislocations in crystalline materials, including their role in trace element mobility, play a vital function in the way these materials respond to an applied stress. However, the mechanisms by which dislocations nucleate in minerals remain poorly understood. Prevailing models for dislocation nucleation include generation by Frank-Read sources, stress localization at crack-tips, atomic segregation, and free surface nucleation by critical stress-gradient criterion. Based on recent APT data from naturally-deformed pyrite, combined with electron backscatter diffraction (EBSD) mapping and ECC imaging, we propose a new nucleation mechanism where dislocations are generated by the local stress field in the vicinity of fluid inclusions. The investigated sample consists of a polycrystalline pyrite aggregate within a black shale host rock that has witnessed a peak temperature of 300°C. The combined EBSD and ECCI results reveal crystal plasticity in the form of lattice misorientation up to 8.5° and low-angle grain boundary development. APT data reveals nanoscale fluid inclusions enriched in As, O (H<sub>2</sub>O), Na and K as well as As- and Co-rich dislocations linked by fluid inclusions. This new model is the first documentation with APT methods of fluid inclusions (voids) in minerals, nanoscale features that are commonly misinterpreted as element clusters or chemically-enriched crystal-defects. The combined data has significant trans-disciplinary implications to the geosciences (structural geology, geochemistry, economic geology, geochronology), the material sciences (metals, ceramics, polymers), and analytical microscopy. Within geochronology voids and dislocations such as these in dated minerals may host elements or isotopes that negatively affect their age. Within ore deposit geology, voids in precious metal-hosting minerals may act as the necessary traps to structurally prevent the metals (gold, silver, copper) from migrating or diffusing out of the host mineral. In material sciences, the presence of such crystalline features can either limit or enhance the performance of engineering materials. Thus, performing APT analysis on crystalline material can help us better understand and predict their physical properties.</p>

scholarly journals Direct observation of site-specific dopant substitution in Si doped (Al x Ga1− x )2O3 via atom probe tomography

2021 ◽  
Vol 54 (18) ◽  
pp. 184001
Author(s):  
Jith Sarker ◽  
A F M Anhar Uddin Bhuiyan ◽  
Zixuan Feng ◽  
Hongping Zhao ◽  
Baishakhi Mazumder
Keyword(s):  
Direct Observation ◽  
Atom Probe Tomography ◽  
Atom Probe ◽  
Site Specific ◽  
Si Doped

scholarly journals Simplifying Observation of Hydrogen Trapping in Atom Probe Tomography

2017 ◽  
Vol 23 (S1) ◽  
pp. 620-621
Author(s):  
Yi-Sheng Chen ◽  
Daniel Haley ◽  
Paul A.J. Bagot ◽  
Michael P. Moody
Keyword(s):  
Atom Probe Tomography ◽  
Atom Probe ◽  
Hydrogen Trapping

scholarly journals Multiple Influences of Molybdenum on the Precipitation Process in a Martensitic PH Stainless Steel

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1118
Author(s):  
Mattias Thuvander ◽  
Marcus Andersson ◽  
Krystyna Stiller
Keyword(s):  
Electron Microscopy ◽  
Stainless Steel ◽  
Atom Probe Tomography ◽  
Precipitation Hardening ◽  
Atom Probe ◽  
Precipitation Process ◽  
Transmission Electron ◽  
Initial Stage ◽  
The Matrix ◽  
Mo Content

Molybdenum has been found to influence the complex precipitation process in a martensitic precipitation hardening stainless steel during aging at 475 °C in several different ways. Three steels with different Mo content (0, 1.2 and 2.3 at.%) were investigated. Studies of the microstructure were performed with atom probe tomography and energy filtered transmission electron microscopy. It is shown that, at the initial stage of aging, a faster nucleation of Cu-rich clusters takes place with increasing Mo content. The Cu-clusters act as precipitation sites for other solute elements and promote the nucleation of Ni-rich phases. During further aging, a higher Mo content in the material instead slows down the growth and coarsening of the Ni-rich phases, because Mo segregates to the interface between precipitate and matrix. Additionally, Mo promotes decomposition of the matrix into α and α′ regions. After longer aging times (>40 h) quasicrystalline Mo-rich R′ phase forms (to a greater extent in the material having the highest Mo content). The observations serve to understand the hardness evolution during aging.

scholarly journals Direct Observation of Hydrogen in Cold-Drawn Pearlitic Steel Wires Using Cryogenic Atom Probe Tomography

2019 ◽  
Vol 25 (S2) ◽  
pp. 2522-2523
Author(s):  
Andrew J Breen ◽  
Yujiao Li ◽  
Leigh Stephenson ◽  
Baptiste Gault ◽  
Michael Herbig
Keyword(s):  
Direct Observation ◽  
Atom Probe Tomography ◽  
Pearlitic Steel ◽  
Atom Probe ◽  
Steel Wires

scholarly journals Carbide Precipitation in a Low Alloyed Steel during Aging Studied by Atom Probe Tomography and Thermodynamic Modeling

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2009
Author(s):  
Mattias Thuvander ◽  
Hans Magnusson ◽  
Ulrika Borggren
Keyword(s):  
Atom Probe Tomography ◽  
Precipitation Hardening ◽  
Atom Probe ◽  
Carbide Precipitation ◽  
Martensitic Structure ◽  
Number Density ◽  
High Number Density ◽  
Molybdenum Carbides ◽  
The Matrix ◽  
Low Alloyed Steel

Carbide precipitation in martensitic low alloyed steels contributes to the mechanical properties through precipitation hardening. A high number density of carbides is desired to maximize the hardening effect, which is achieved through the precipitation of carbides on the dislocations in the martensitic structure. In this study, the nucleation, growth, and coarsening of vanadium and molybdenum carbides during aging at 600 °C for periods up to four weeks were investigated. The work covers characterization with atom probe tomography, which showed that the nucleation of V and Mo rich MC/M2C carbides takes place on dislocations. The growth of these carbides proceeds by the diffusion of elements to the dislocations, which has been modeled using Dictra software, confirming the rate of the reaction as well as the depletion of carbide formers in the matrix. For longer aging times, particle coarsening will decrease the number density of particles with a transition from dislocation-based carbides to separate rounded carbides.

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