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Overcoming challenges in the study of nitrided microalloyed steels using atom probe
Kelvin Y Xie1, Andrew J Breen, Lan Yao
1Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006, Australia. kelvin.xie@sydney.edu.au
Ultramicroscopy
|November 19, 2011
Summary
Atom probe tomography (APT) using laser pulses effectively minimizes spectral artifacts in nitrided steels. This technique improves compositional accuracy and spatial resolution for studying advanced engineering materials.
Area of Science:
- Materials Science
- Analytical Chemistry
- Metallurgy
Background:
- Nitrided steels offer excellent hardness and are vital in engineering applications.
- Atom probe tomography (APT) is a powerful technique for analyzing material composition at the atomic scale.
- Studying nitrogen (N) and niobium (Nb) microalloyed steels using APT presents challenges due to mass spectral artifacts.
Purpose of the Study:
- To investigate the impact of N content on Nb-microalloyed CASTRIP steels using APT.
- To identify and mitigate spectral artifacts, specifically Fe peak tails, that affect compositional accuracy.
- To optimize APT parameters for enhanced analysis of nitrided steels.
Main Methods:
- Utilized atom probe tomography (APT) on two Nb-microalloyed CASTRIP steels with varying N content.
- Compared voltage pulsing with pulsed-laser APT, varying laser energies from 0.2 to 1.2 nJ.
- Analyzed mass spectra to identify and quantify spectral tails and assess compositional accuracy and spatial resolution.
Main Results:
- Observed significant Fe peak tails in mass spectra, leading to overestimated Nb and Cu compositions, particularly with voltage pulsing.
- Pulsed-laser APT with laser energies between 0.2–1.2 nJ successfully reduced spectral tails.
- Optimal laser energy of ~0.4 nJ improved mass resolution without significantly degrading z-direction spatial resolution, though x-y resolution decreased with higher laser energy.
Conclusions:
- Pulsed-laser APT is superior to voltage pulsing for analyzing nitrided steels by reducing spectral artifacts.
- A laser energy of approximately 0.4 nJ offers a balance between improved mass resolution and preserved spatial resolution.
- Optimized pulsed-laser APT provides more accurate compositional analysis of Nb-microalloyed steels.
