The role of Ti and TiC nanoprecipitates in radiation resistant austenitic steel: A nanoscale study

Niels Cautaerts; Rémi Delville; Erich Stergar; Janne Pakarinen; Marc Verwerft; Yong Yang; Christina Hofer; Ronald Schnitzer; Steffen Lamm; Peter Felfer; Dominique Schryvers

doi:10.1016/j.actamat.2020.07.022

The role of Ti and TiC nanoprecipitates in radiation resistant austenitic steel: A nanoscale study

Niels Cautaerts^*
, Rémi Delville
, Erich Stergar
, Janne Pakarinen
, Marc Verwerft
, Yong Yang
, Christina Hofer
, Ronald Schnitzer
, Steffen Lamm
, Peter Felfer
, Dominique Schryvers

^*Corresponding author for this work

BA5513 Materials for emerging technologies

Research output: Contribution to journal › Article › Scientific › peer-review

21 Citations (Scopus)

Abstract

This work encompasses an in-depth transmission electron microscopy and atom probe tomography study of Ti-stabilized austenitic steel irradiated with Fe-ions. The focus is on radiation induced segregation and precipitation, and in particular on how Ti and TiC affect these processes. A 15-15Ti steel (grade: DIN 1.4970) in two thermo-mechanical states (cold-worked and aged) was irradiated at different temperatures up to a dose of 40 dpa. At low irradiation temperatures, the cold-worked and aged materials evolved to a similar microstructure dominated by small Si and Ni clusters, corresponding to segregation to small point defect clusters. TiC precipitates, initially present in the aged material, were found to be unstable under these irradiation conditions. Elevated irradiation temperatures resulted in the nucleation of nanometer sized Cr enriched TiC precipitates surrounded by Si and Ni enriched shells. In addition, nanometer sized Ti- and Mn-enriched G-phase (M₆Ni₁₆Si₇) precipitates formed, often attached to TiC precipitates. Post irradiation, larger number densities of TiC were observed in the cold-worked material compared to the aged material. This was correlated with a lower volume fraction of G-phase. The findings suggest that at elevated irradiation temperatures, the precipitate-matrix interface is an important point defect sink and contributes to the improved radiation resistance of this material. The study is a first of its kind on stabilized steel and demonstrates the significance of the small Ti addition to the evolution of the microstructure under irradiation.

Original language	English
Pages (from-to)	184-197
Number of pages	14
Journal	Acta Materialia
Volume	197
DOIs	https://doi.org/10.1016/j.actamat.2020.07.022
Publication status	Published - 15 Sept 2020
MoE publication type	A1 Journal article-refereed

Funding

This work was supported by ENGIE [contract number 2015-AC-007 e BSUEZ6900]; the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment; and by the MYRRHA program at SCK-CEN, Belgium. Funding of the Austrian BMK (846933) in the framework of the program ”Production of the future” and the ”BMK Professorship for Industry” is gratefully acknowledged. We want to thank the staff at MIBL for assisting with the ion irradiations as well as the staff at CAES for assisting with FIB work and conducting APT measurements.

Keywords

APT
Austenitic steel
G-phase
Precipitation
Radiation induced segregation
TEM
TiC

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10.1016/j.actamat.2020.07.022

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title = "The role of Ti and TiC nanoprecipitates in radiation resistant austenitic steel: A nanoscale study",

abstract = "This work encompasses an in-depth transmission electron microscopy and atom probe tomography study of Ti-stabilized austenitic steel irradiated with Fe-ions. The focus is on radiation induced segregation and precipitation, and in particular on how Ti and TiC affect these processes. A 15-15Ti steel (grade: DIN 1.4970) in two thermo-mechanical states (cold-worked and aged) was irradiated at different temperatures up to a dose of 40 dpa. At low irradiation temperatures, the cold-worked and aged materials evolved to a similar microstructure dominated by small Si and Ni clusters, corresponding to segregation to small point defect clusters. TiC precipitates, initially present in the aged material, were found to be unstable under these irradiation conditions. Elevated irradiation temperatures resulted in the nucleation of nanometer sized Cr enriched TiC precipitates surrounded by Si and Ni enriched shells. In addition, nanometer sized Ti- and Mn-enriched G-phase (M6Ni16Si7) precipitates formed, often attached to TiC precipitates. Post irradiation, larger number densities of TiC were observed in the cold-worked material compared to the aged material. This was correlated with a lower volume fraction of G-phase. The findings suggest that at elevated irradiation temperatures, the precipitate-matrix interface is an important point defect sink and contributes to the improved radiation resistance of this material. The study is a first of its kind on stabilized steel and demonstrates the significance of the small Ti addition to the evolution of the microstructure under irradiation.",

keywords = "APT, Austenitic steel, G-phase, Precipitation, Radiation induced segregation, TEM, TiC",

author = "Niels Cautaerts and R{\'e}mi Delville and Erich Stergar and Janne Pakarinen and Marc Verwerft and Yong Yang and Christina Hofer and Ronald Schnitzer and Steffen Lamm and Peter Felfer and Dominique Schryvers",

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T1 - The role of Ti and TiC nanoprecipitates in radiation resistant austenitic steel

T2 - A nanoscale study

AU - Cautaerts, Niels

AU - Delville, Rémi

AU - Stergar, Erich

AU - Pakarinen, Janne

AU - Verwerft, Marc

AU - Yang, Yong

AU - Hofer, Christina

AU - Schnitzer, Ronald

AU - Lamm, Steffen

AU - Felfer, Peter

AU - Schryvers, Dominique

PY - 2020/9/15

Y1 - 2020/9/15

N2 - This work encompasses an in-depth transmission electron microscopy and atom probe tomography study of Ti-stabilized austenitic steel irradiated with Fe-ions. The focus is on radiation induced segregation and precipitation, and in particular on how Ti and TiC affect these processes. A 15-15Ti steel (grade: DIN 1.4970) in two thermo-mechanical states (cold-worked and aged) was irradiated at different temperatures up to a dose of 40 dpa. At low irradiation temperatures, the cold-worked and aged materials evolved to a similar microstructure dominated by small Si and Ni clusters, corresponding to segregation to small point defect clusters. TiC precipitates, initially present in the aged material, were found to be unstable under these irradiation conditions. Elevated irradiation temperatures resulted in the nucleation of nanometer sized Cr enriched TiC precipitates surrounded by Si and Ni enriched shells. In addition, nanometer sized Ti- and Mn-enriched G-phase (M6Ni16Si7) precipitates formed, often attached to TiC precipitates. Post irradiation, larger number densities of TiC were observed in the cold-worked material compared to the aged material. This was correlated with a lower volume fraction of G-phase. The findings suggest that at elevated irradiation temperatures, the precipitate-matrix interface is an important point defect sink and contributes to the improved radiation resistance of this material. The study is a first of its kind on stabilized steel and demonstrates the significance of the small Ti addition to the evolution of the microstructure under irradiation.

AB - This work encompasses an in-depth transmission electron microscopy and atom probe tomography study of Ti-stabilized austenitic steel irradiated with Fe-ions. The focus is on radiation induced segregation and precipitation, and in particular on how Ti and TiC affect these processes. A 15-15Ti steel (grade: DIN 1.4970) in two thermo-mechanical states (cold-worked and aged) was irradiated at different temperatures up to a dose of 40 dpa. At low irradiation temperatures, the cold-worked and aged materials evolved to a similar microstructure dominated by small Si and Ni clusters, corresponding to segregation to small point defect clusters. TiC precipitates, initially present in the aged material, were found to be unstable under these irradiation conditions. Elevated irradiation temperatures resulted in the nucleation of nanometer sized Cr enriched TiC precipitates surrounded by Si and Ni enriched shells. In addition, nanometer sized Ti- and Mn-enriched G-phase (M6Ni16Si7) precipitates formed, often attached to TiC precipitates. Post irradiation, larger number densities of TiC were observed in the cold-worked material compared to the aged material. This was correlated with a lower volume fraction of G-phase. The findings suggest that at elevated irradiation temperatures, the precipitate-matrix interface is an important point defect sink and contributes to the improved radiation resistance of this material. The study is a first of its kind on stabilized steel and demonstrates the significance of the small Ti addition to the evolution of the microstructure under irradiation.

KW - APT

KW - Austenitic steel

KW - G-phase

KW - Precipitation

KW - Radiation induced segregation

KW - TEM

KW - TiC

UR - https://www.scopus.com/pages/publications/85088626589

U2 - 10.1016/j.actamat.2020.07.022

DO - 10.1016/j.actamat.2020.07.022

M3 - Article

AN - SCOPUS:85088626589

SN - 1359-6454

VL - 197

SP - 184

EP - 197

JO - Acta Materialia

JF - Acta Materialia

ER -

The role of Ti and TiC nanoprecipitates in radiation resistant austenitic steel: A nanoscale study

Abstract

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Keywords

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