Atom positions in steel

I was able to make some data sets available this year from work published in 2004 and in 2017 showing how atoms arrange themselves in nanostructured steel (Super Bainite).

There are a couple of motivations for making the data sets available. Firstly it is good practice and makes it possible for others to analyse the data to check reproducibility of my work, and there is also possibility to extract further information. It also serves as a back-up for the data sets by putting them on internet, one of the best back-ups available… 🙂

Another is that, at the time of conducting these experiments a frustration of mine was that there was no [simple] way to view the positions without access to commercial software, for me, that was once I had left the facility I visited to undertake part of the work. Hopefully the sharing of atom position data will become more standard procedure in future, with the increasing sophistication of high-level computing languages and expansion of open software. This may allow new developments in reconstruction of volumes, analysis of the atom positions, and education of users; benefiting the atom probe field.

The data were collected by using a pulsed electric field concentrated on the tip of a needle made by electropolishing the steel sample. By pulsing the voltage both the time-of-flight and the position the projected atom hits a detector screen can be recorded. This can then be mapped back to the sample volume, allowing measurement of the composition of the steel with better than nanometre resolution. The technique is called 3D atom probe (3DAP) tomographic atom probe (TAP) or atom probe tomography (APT). This technique is related to field ion microscopy.

The volume studied include volumes from various crystal structures (BCC bainitic ferrite, FCC thin-film austenite, carbides such as Fe3C cementite) in the particular steel I was studying (nanostructured carbide-free bainite — see papers for details).

Data can be found here:
https://www.repository.cam.ac.uk/handle/1810/265717
https://www.repository.cam.ac.uk/handle/1810/265720

The papers describing the data can be found here:

https://www.phase-trans.msm.cam.ac.uk/2004/atom.probe.bainite.html

https://www.repository.cam.ac.uk/handle/1810/263230

I’m glad to make these data sets available, and hope they will continue to be available in the future from the Cambridge repository website.

At the time I did the experiments, only commercial software was available to view the atom probe data such as IVAS ivas, but today I believe it should be possible to view the atom positions using software such as 3depict 3d epict.

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2 Responses

  1. Hi,

    3Depict author here: Your .ops files showed some limitations in the current 3depict OPS parsing routines. I’ve fixed this in our internal repository. This will be published in the next version (should be 0.0.21).

    The bugs were that the program did not correctly handle trailing whitespace, or repeated whitespace (my test files used either single tab or space separators, rather than repeated space) in OPS files.

    The example dataset is a very good thing to have, and helps us fix bugs in our program.

    I did note that the range file data appears to be missing. It is possible to write one by hand (the capability to generate one does kind-of exist in 3depict, but is a little clunkier than we would like).

    If you do have the range files from the analysis, (the original ones used), or the .root files (these would be in your ivas folder – defaults to NetBeans (or something), if you have one), then including it in the Cambridge repository would be great!

    Thanks for taking the time to upload the data, in a public way.

  2. I had a look around in my lab books and I don’t have a record of the ranges there, and I couldn’t find a file before so that’s why they are not in the repository. I think it would only be possible to vary the ranges until processing the files generates the same composition profiles.

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