An improved reconstruction procedure for the correction of local magnification effects in three-dimensional atom-probe

A new 3DAP reconstruction procedure is proposed that accounts for the evaporation field of a secondary phase. It applies the existing cluster selection software to identify the atoms of the second phase and, subsequently, an iterative algorithm to homogenise the volume laterally. This Procedure, easily implementable on existing reconstruction software, has been applied successfully on simulated and real 3DAP analyses

Low temperature precipitation kinetics of niobium nitride platelets in Fe

International audienceSingle plane platelets of niobium nitride have been observed to form in a Fe-Nb-N alloy during ageing at 600 degrees C, using High Resolution Electron Microscopy, Field Ion Microscopy and Atom Probe Tomography. Small-angle neutron scattering has been used to investigate the kinetics of formation of these platelets. They are shown to nucleate in less than 5 min at this ageing temperature, and subsequently to grow in-plane to a size of about 10 nm without experiencing any change in thickness

Kinetics pathway of precipitation in model Co-Al-W superalloy

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Impact of directional walk on atom probe microanalysis

In the atom probe microanalysis of steels, inconsistencies in the measured compositions of solutes (C, N) have often been reported, as well as their appearance as molecular ions. Here we propose that these issues might arise from surface migration of solute atoms over the specimen surface. Surface migration of solutes is evidenced by field-ion microscopy observations, and its consequences on atom probe microanalysis are detailed for a wide range of solute (P, Si, Mn, B, C and N). It is proposed that directional walk driven by field gradients over the specimen surface and thermally activated is the prominent effect

Basics of Field Ion Microscopy

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Basics of Field Ion Microscopy

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Atom probe tomography investigation of assisted precipitation of secondary hardening carbides in a medium carbon martensitic steels

International audienceA medium carbon martensitic steel containing nanometer scale secondary hardening carbides and intermetallic particles is investigated by field ion microscopy and atom probe tomography. The interaction between the concomitant precipitations of both types of particles is investigated. It is shown that the presence of the intermetallic phase affects the nucleation mechanism and the spatial distribution of the secondary hardening carbides, which shifts from heterogeneous on dislocations to heterogeneous on the intermetallic particles

Atom Probe Studies of the Fe–Cr System and Stainless Steels Aged at Intermediate Temperature

International audienceThe a–a9 spinodal decomposition is known to occurr in iron–chromium-based model andindustrial alloys during long-term aging at intermediate temperatures. This decompositioncan be characterized unambiguously by atom probe, and its evolution quantified by meansof various microstructural paramaters directly accessible from concentration profiles. Com-parison with the existing theories of spinodal decomposition will be briefly examined. Thisdecomposition has a direct influence on the material, and can be used to improve magneticor mechanical properties. Conversely, some mechanical properties, such as impact tough-ness, are greatly degradated by this evolution, and can lead to serious problems when, forexample, the integrity of large industrial components is affected. For this reason, extensivework has been carried out to understand the influence of the various alloying elements onthe phase separation and on the embrittlement process. Atom probe contributions in thisarea will be presented in this paper

Atom probe tomography investigation of assisted precipitation of secondary hardening carbides in a medium carbon martensitic steels

International audienceA medium carbon martensitic steel containing nanometer scale secondary hardening carbides and intermetallic particles is investigated by field ion microscopy and atom probe tomography. The interaction between the concomitant precipitations of both types of particles is investigated. It is shown that the presence of the intermetallic phase affects the nucleation mechanism and the spatial distribution of the secondary hardening carbides, which shifts from heterogeneous on dislocations to heterogeneous on the intermetallic particles