Quantification of APT physical limitations on chemical composition of precipitates in Fe–Cr alloys

Abstract

a b s t r a c tAmong the different nano-features at the origin of embrittlement of FeeCr alloys and steels, a 0 precipitates play a major role in alloys with Cr content higher than about 10at.%. If Atom Probe Tomography (APT) is recognized as an efficient technique for characterizing a 0 precipitates, discussions remain on its ability to measure the actual composition of small particles. Two APT limitations are at the origin of these discussions: its lateral resolution (and on a smaller scale the depth resolution) and local magnification effects due to the difference in field evaporations between the matrix and the particles. In this study, the impacts of these two limitations are quantified for the first time using numerical approaches and an analytical model. This will provide an overview of the interpretation for the a' particles chemical composition experimentally measured by APT.The results show that: (i) the major effect of local magnification is ion focussing with no mixing in the core of the particles for particle radius larger than 1 nm, (ii) lateral resolution is the main contributor to the composition bias. Depending on the lateral resolution, the core of the small particles may be diluted by matrix atoms but the dilution does not exceed 5.2 at.%. The extent of the decrease in measured Cr concentration of the particles depends on the Cr concentration difference between particles and the surrounding matrix.

Data on Cu- and Ni-Si-Mn-rich solute clustering in a neutron irradiated austenitic stainless steel

“…After Cu-rich clusters were identified by OSCAR, clusters were examined for evidence of trajectory aberrations. This analysis was done by measuring the relative atomic density across clusters in the x-direction, similar to as in [2] , [3] . Here, relative atomic density is the ratio of the locally measured atomic density, , to the measured bulk atomic density, .…”

Effect of Ni, Mo and Mn content on spinodal decomposition kinetics and G-phase precipitation of aged model cast austenitic stainless steels

“…At 400 °C, for more concentrated particles, a small evaporation field contrast appears revealing that G-phase particles have a slightly higher evaporation field than  and ' zones. In such a case, no matrix atoms enter the precipitates and trajectory overlaps are expected to only impact interfaces [28][29][30].…”

A Combinatorial Approach to Reliable Quantitative Analysis of Small Nano-Sized Precipitates: A Case Study with α′ Precipitates in Fe–20 at% Cr Alloy

“…In fact, this type of variation in the average cluster composition is not uncommon for the analysis method that is followed in the implementation of cluster search algorithm. In spite of this, the cluster core composition can still be comparable to the one derived by numerical simulation (Hatzoglou et al, 2019). Similarly, the selection of the appropriate threshold value for isoconcentration surfaces is crucial in achieving reliable quantitative precipitation analysis (Barton et al, 2019).…”