Thermodynamics of an austenitic stainless steel (AISI-348) under in situ TEM heavy ion irradiation

Matheus A. Tunes, Graeme Greaves, Thomas Kremmer, Vladimir M. Vishnyakov, Philip D. Edmondson, Stephen E. Donnelly, Stefan Pogatscher, Cláudio G. Schön

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The stability of the face-centred cubic austenite (γ-Fe) phase in a commercial stainless steel (AISI-348) was investigated through in situ transmission electron microscopy (TEM) with heavy ion irradiation at 1073 K up to a fluence of 1.3×10 17 ions⋅cm −2 (corresponding to a dose of 46 dpa). The γ-Fe phase was observed to decompose at a fluence of around 7.8×10 15 ions⋅cm −2 (3 dpa) when a new phase nucleated and grew upon increasing irradiation dose. Scanning transmission electron microscopy (STEM) with energy dispersive X-ray (EDX) spectroscopy and multivariate statistical analysis (MVSA) were used to characterise the irradiated specimens. The combination of such experimental techniques with calculated equilibrium phase diagrams using the CALPHAD method led to the conclusion that the new phase formed upon irradiation is the body-centred cubic Cr-rich α' phase. At the nanoscale, precipitation of M 23C 6 (τ-carbide) was also observed. The results indicate that ion irradiation can assist the austenitic stainless steel to reach a non-equilibrium state similar to a calculated equilibrium state observed at lower temperatures.

Seiten (von - bis)360-371
FachzeitschriftActa Materialia
Ausgabenummer15 October
PublikationsstatusElektronische Veröffentlichung vor Drucklegung. - 27 Aug. 2019

Bibliographische Notiz

Funding Information:
The authors are grateful to the European Research Council ( ERC ) excellent science grant “TRANSDESIGN” through the Horizon 2020 programme under contract 757961 and by the financial support from the Austrian Research Promotion Agency ( FFG ) in the project 3DnanoAnalytics (FFG-No 858040 ). All the authors are grateful to the Engineering and Physical Sciences Research Council ( EPRSC ) for funding MIAMI facilities under the grants EP/E017266/1 and EP/M028283/1 . MAT acknowledges previous support from ASTRO – a United States Department of Energy workforce development program implemented at Oak Ridge National Laboratory through the Oak Ridge Institute for Science and Education under contract number DE-AC05-06OR23100 . CGS acknowledges partial financial support by the São Paulo State Research Funding Agency ( FAPESP , São Paulo, Brazil), under grant no. 2016/25248-3 and by the Brazilian National Research Council ( CNPq , Brasília, Brazil) under the grant no. 312424/2013-2 . MAT and CGS thank Dr. Nathanael W.S. Morais ( USP ) for cross-checking the AISI-348 elemental composition analysis presented in this paper. MAT and VMV would like to thank and to Prof. U. Bangert (UL) and Dr. A. Harvey (UL) by previous support with electron microscopy. The authors thank Univ.-Prof. Ernst Kozeschnik (TU Wien) for his deep appreciation of this present work and for the useful discussions on the thermodynamics of austenitic stainless steels. MAT would like to thank Univ.-Prof. Helmut Antrekowitsch (MU Leoben), Univ.-Prof. Peter J. Uggowitzer (MU Leoben/ETHz), Ms. Claudia Hackl (MU Leoben) and all the team (MU Leoben) for all the provided support and warm reception in Austria.

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