Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range

Hiroyasu Tanigawa; Mikhail A. Sokolov; Atsushi Sawahata; Naoyuki Hashimoto; Masami Ando; Kiyoyuki Shiba; Masato Enomoto; Ronald L. Klueh

doi:10.1520/JAI101728

Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range

Hiroyasu Tanigawa, Mikhail A. Sokolov, Atsushi Sawahata, Naoyuki Hashimoto, Masami Ando, Kiyoyuki Shiba, Masato Enomoto, Ronald L. Klueh

Advanced Nuclear Materials

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

1 Scopus citations

Abstract

The master curve method for analyzing fracture toughness data depends on the assumption that the fracture initiation points are homogeneously distributed and fracture initiation is independent of test temperature. The reduced-activation ferritic/martensitic steels, such as F82H (Fe-8Cr-2W-0.2V-0.04Ta), form Al₂O₃-Ta(V,Ti)O composite inclusions and its distribution is not homogeneous throughout one heat, and this microstructural inhomogeneity appears to be correlated with bimodal facture of F82H in the transition range. To investigate this possibility, 1TCT fracture toughness specimens of F82H-IEA steel were fatigue precracked and sliced through the specimen thickness for microstructure analysis around the crack. It was found that the crack penetration was straight in the beginning, and then tended to follow a prior austenite grain boundary and finally to branch into two or three different directions. In addition, the microstructures around the crack and ahead of the crack formed a cell structure and became softer than nearby regions, which is typical for fatigue-loaded F82H. Possible mechanisms for how this cell structure ahead of cracks affects fracture toughness are suggested.

Original language	English
Title of host publication	Small Specimen Test Techniques
Subtitle of host publication	5th Volume
Publisher	American Society for Testing and Materials
Pages	122-135
Number of pages	14
ISBN (Print)	9780803145061
DOIs	https://doi.org/10.1520/JAI101728
State	Published - 2009
Event	5th Symposium on Small Specimen Test Techniques - Anaheim, CA, United States Duration: Jan 31 2007 → Feb 1 2007

Publication series

Name	ASTM Special Technical Publication
Volume	1502 STP
ISSN (Print)	0066-0558

Conference

Conference	5th Symposium on Small Specimen Test Techniques
Country/Territory	United States
City	Anaheim, CA
Period	01/31/07 → 02/1/07

Keywords

Bimodal fracture
Precracking
RAFM
Ta rich inclusion

Access to Document

10.1520/JAI101728

Cite this

Tanigawa, H., Sokolov, M. A., Sawahata, A., Hashimoto, N., Ando, M., Shiba, K., Enomoto, M., & Klueh, R. L. (2009). Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range. In Small Specimen Test Techniques: 5th Volume (pp. 122-135). (ASTM Special Technical Publication; Vol. 1502 STP). American Society for Testing and Materials. https://doi.org/10.1520/JAI101728

Tanigawa, Hiroyasu ; Sokolov, Mikhail A. ; Sawahata, Atsushi et al. / Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range. Small Specimen Test Techniques: 5th Volume. American Society for Testing and Materials, 2009. pp. 122-135 (ASTM Special Technical Publication).

@inproceedings{792344407d474e1ab013669926b33fba,

title = "Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range",

abstract = "The master curve method for analyzing fracture toughness data depends on the assumption that the fracture initiation points are homogeneously distributed and fracture initiation is independent of test temperature. The reduced-activation ferritic/martensitic steels, such as F82H (Fe-8Cr-2W-0.2V-0.04Ta), form Al2O3-Ta(V,Ti)O composite inclusions and its distribution is not homogeneous throughout one heat, and this microstructural inhomogeneity appears to be correlated with bimodal facture of F82H in the transition range. To investigate this possibility, 1TCT fracture toughness specimens of F82H-IEA steel were fatigue precracked and sliced through the specimen thickness for microstructure analysis around the crack. It was found that the crack penetration was straight in the beginning, and then tended to follow a prior austenite grain boundary and finally to branch into two or three different directions. In addition, the microstructures around the crack and ahead of the crack formed a cell structure and became softer than nearby regions, which is typical for fatigue-loaded F82H. Possible mechanisms for how this cell structure ahead of cracks affects fracture toughness are suggested.",

keywords = "Bimodal fracture, Precracking, RAFM, Ta rich inclusion",

author = "Hiroyasu Tanigawa and Sokolov, {Mikhail A.} and Atsushi Sawahata and Naoyuki Hashimoto and Masami Ando and Kiyoyuki Shiba and Masato Enomoto and Klueh, {Ronald L.}",

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language = "English",

isbn = "9780803145061",

series = "ASTM Special Technical Publication",

publisher = "American Society for Testing and Materials",

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Tanigawa, H, Sokolov, MA, Sawahata, A, Hashimoto, N, Ando, M, Shiba, K, Enomoto, M & Klueh, RL 2009, Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range. in Small Specimen Test Techniques: 5th Volume. ASTM Special Technical Publication, vol. 1502 STP, American Society for Testing and Materials, pp. 122-135, 5th Symposium on Small Specimen Test Techniques, Anaheim, CA, United States, 01/31/07. https://doi.org/10.1520/JAI101728

Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range. / Tanigawa, Hiroyasu; Sokolov, Mikhail A.; Sawahata, Atsushi et al.
Small Specimen Test Techniques: 5th Volume. American Society for Testing and Materials, 2009. p. 122-135 (ASTM Special Technical Publication; Vol. 1502 STP).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

TY - GEN

T1 - Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range

AU - Tanigawa, Hiroyasu

AU - Sokolov, Mikhail A.

AU - Sawahata, Atsushi

AU - Hashimoto, Naoyuki

AU - Ando, Masami

AU - Shiba, Kiyoyuki

AU - Enomoto, Masato

AU - Klueh, Ronald L.

PY - 2009

Y1 - 2009

N2 - The master curve method for analyzing fracture toughness data depends on the assumption that the fracture initiation points are homogeneously distributed and fracture initiation is independent of test temperature. The reduced-activation ferritic/martensitic steels, such as F82H (Fe-8Cr-2W-0.2V-0.04Ta), form Al2O3-Ta(V,Ti)O composite inclusions and its distribution is not homogeneous throughout one heat, and this microstructural inhomogeneity appears to be correlated with bimodal facture of F82H in the transition range. To investigate this possibility, 1TCT fracture toughness specimens of F82H-IEA steel were fatigue precracked and sliced through the specimen thickness for microstructure analysis around the crack. It was found that the crack penetration was straight in the beginning, and then tended to follow a prior austenite grain boundary and finally to branch into two or three different directions. In addition, the microstructures around the crack and ahead of the crack formed a cell structure and became softer than nearby regions, which is typical for fatigue-loaded F82H. Possible mechanisms for how this cell structure ahead of cracks affects fracture toughness are suggested.

AB - The master curve method for analyzing fracture toughness data depends on the assumption that the fracture initiation points are homogeneously distributed and fracture initiation is independent of test temperature. The reduced-activation ferritic/martensitic steels, such as F82H (Fe-8Cr-2W-0.2V-0.04Ta), form Al2O3-Ta(V,Ti)O composite inclusions and its distribution is not homogeneous throughout one heat, and this microstructural inhomogeneity appears to be correlated with bimodal facture of F82H in the transition range. To investigate this possibility, 1TCT fracture toughness specimens of F82H-IEA steel were fatigue precracked and sliced through the specimen thickness for microstructure analysis around the crack. It was found that the crack penetration was straight in the beginning, and then tended to follow a prior austenite grain boundary and finally to branch into two or three different directions. In addition, the microstructures around the crack and ahead of the crack formed a cell structure and became softer than nearby regions, which is typical for fatigue-loaded F82H. Possible mechanisms for how this cell structure ahead of cracks affects fracture toughness are suggested.

KW - Bimodal fracture

KW - Precracking

KW - RAFM

KW - Ta rich inclusion

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U2 - 10.1520/JAI101728

DO - 10.1520/JAI101728

M3 - Conference contribution

AN - SCOPUS:72849126599

SN - 9780803145061

T3 - ASTM Special Technical Publication

SP - 122

EP - 135

BT - Small Specimen Test Techniques

PB - American Society for Testing and Materials

T2 - 5th Symposium on Small Specimen Test Techniques

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ER -

Tanigawa H, Sokolov MA, Sawahata A, Hashimoto N, Ando M, Shiba K et al. Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range. In Small Specimen Test Techniques: 5th Volume. American Society for Testing and Materials. 2009. p. 122-135. (ASTM Special Technical Publication). doi: 10.1520/JAI101728

Effect of Ta rich inclusions and microstructure change during precracking on bimodal fracture of reduced-activation ferritic/martensitic steels observed in transition range

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