Measurement of Local Mechanical Properties of T91 Steel Corroded by Molten Lead-Bismuth Eutectic Alloy via Micropillar C
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.36
Measurement of Local Mechanical Properties of T91 Steel Corroded by Molten Lead-Bismuth Eutectic Alloy via Micropillar Compression Test K. Kaede1, A. Jäger2, V. Gärtnerová3, C. Takushima1, T. Yamamuro4, S. Tsurekawa5* 1 Department of Materials Science and Engineering, Graduate School of Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan
2 Department of Mechanics, Faculty of Civil Engineering, Czech Technical University, Prague, Czech Republic
3
Struers GmbH, Scientific and Technological Park, Roztoky, Czech Republic
4
Technical Division, Faculty of Engineering, Kumamoto University, Kumamoto, 860-8555, Japan
5 Structural Materials, Division of Materials Science, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan
* Corresponding author: [email protected]
ABSTRACT
T91 ferritic/martensitic (F/M) steel is an expected structural material candidate for Gen IV liquid lead-bismuth cooled nuclear reactors. However, molten lead-bismuth eutectic alloy (mLBE) often causes liquid-metal embrittlement (LME) of F/M steels. Although prior austenite grain boundaries and martensite block boundaries were reported to be preferential sites for LME, the mechanism of LME in a T91/LBE couple is yet to be comprehensively understood. In this paper, the effect of mLBE on T91 steel was investigated using micropillar compression tests. mLBE corrosion was found to cause a significant decrease in yield stress. The micropillar made from mLBE-corroded specimen was significantly sheared along high angle boundaries. In addition, EDS analysis demonstrated the presence of Pb/Bi at these high angle boundaries.
1. INTRODUCTION The Gen IV liquid lead alloy-cooled reactor is expected to use the liquid lead-bismuth eutectic alloy as a coolant because of its chemical inertness, high boiling point (1943 K) and high thermal conductivity. T91 ferritic/martensitic
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(F/M) steel is a promising candidate material for structures such as fuel cladding. However, molten lead-bismuth eutectic alloy (mLBE) often causes liquid metal embrittlement (LME) of F/M steels [1]. LME has been reported to occur in several solid metal/liquid metal couples such as Al/Ga [2], Cu/Bi [3] and Ni/Bi [4], and the dominant fracture mode associated with LME is intergranular cracking. Extensive studies on LME for a T91/LBE couple have been conducted to date [5-8]. However, the property of an LME fracture and its mechanism are still not clearly understood. Dai et al. [5] reported that LME was significantly observed in T91 steel after necking of the specimen took place under tensile loading in mLBE, and that the appearance of fracture surfaces was generally brittle manner. Martin et al. [7] rep
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