Abstract
Castable alumina forming austenitic (AFA) alloys have demonstrated superior creep life and oxidation resistance at temperatures exceeding 800⁰C. Despite the success in the applicability of these alloys in extreme environments, there is a limited understanding of the deformation modes and the influence of each alloying element guiding the alloy design strategies that could further enhance the creep strength of these AFA alloys, particularly at temperatures at and above 900⁰C. In this study, we reveal the mechanism underpinning the superior creep performance of castable AFA alloys that involves suppressing primary carbide formation through minor compositional modification. This approach results in a three-fold increase in creep strength at 900⁰C and 50 MPa. By employing integrated characterization techniques, we analyzed the microstructures of two AFA alloys, both before and after the creep process. We discovered that the suppression of primary carbides permits the in-situ clustering of now-available interstitial elements such as C, Si, and O during high-temperature creep. This improved solid solution strengthening and reduced stacking fault energy of the alloy. Moreover, it also enabled controlled secondary carbide formation during testing, further improving the creep resistance. These findings underline the important interplay between alloy composition, microstructure, and creep properties, and offer a promising design strategy for developing economical high-temperature Fe-based alloys suitable for advanced applications.
| Original language | English |
|---|---|
| Article number | 119494 |
| Journal | Acta Materialia |
| Volume | 263 |
| DOIs | |
| State | Published - Jan 15 2024 |
Funding
This research was sponsored by the Powertrain Materials Core Program, DOE Vehicle Technologies Office, and a portion of this research was performed using facilities at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy ’s (DOE's) Biological and Environmental Research program and located at PNNL. PNNL is a multiprogram national laboratory operated by Battelle for the DOE under Contract DEAC05–76RL01830 . This research used resources of the Advanced Photon Source, a DOE Office of Science User Facility operated by Argonne National Laboratory under Contract No. DE-AC02–06CH11357 . ORNL is an Office of Science national laboratory operated by UT-Battelle, LLC , under Contract No. DE-AC05–00OR22725 with the U.S. Department of Energy. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05–00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan) .
| Funders | Funder number |
|---|---|
| Powertrain Materials Core Program | |
| U.S. Department of Energy | |
| Office of Science | |
| Argonne National Laboratory | DE-AC02–06CH11357 |
| Pacific Northwest National Laboratory | DEAC05–76RL01830 |
| UT-Battelle | DE-AC05–00OR22725 |
Keywords
- Alumina forming austenitic alloys
- Creep
- Dislocation
- Microscopy
- Precipitates
- Synchrotron