Investigation of thermal aging effects on the tensile properties of Alloy 617 by in-situ synchrotron wide-angle X-ray scattering

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:651

Article

Liu, Xiang¹  Mo, Kun²  Miao, Yinbin^1,2  Lan, Kuan-Che¹  Zhang, Guangming³  Chen, Wei-Ying^1,2  Tomchik, Carolyn¹  Seibert, Rachel⁴  Terry, Jeff⁴  Stubbins, James F.^1,5 

[1] Univ Illinois, Dept Nucl Plasma & Radiol Engn, Urbana, IL 61801 USA

[2] Argonne Natl Lab, Nucl Engn Div, Lemont, IL 60439 USA

[3] Univ Sci & Technol Beijing, Sch Mat Sci & Engn, Beijing 10083, Peoples R China

[4] IIT, Coll Sci, Chicago, IL 60616 USA

[5] Kyushu Univ, Int Inst Carbon Neutral Energy Res WPI I2CNER, Nishi Ku, Fukuoka 8190395, Japan

关键词: Alloy 617;    High-temperature thermal aging;    Wide-angle X-ray scattering;    M23C6 carbide;   

DOI  :  10.1016/j.msea.2015.10.098

来源: Elsevier

【 摘 要 】

The nickel-base Alloy 617 has been considered as the lead candidate structural material for the intermediate heat exchanger (IHX) of the Very-High-Temperature Reactor (VHTR). In order to assess the long-term performance of Alloy 617, thermal aging experiments up to 10,000 h in duration were performed at 1000 degrees C. Subsequently, in-situ synchrotron wide-angle X-ray scattering (WAXS) tensile tests were carried out at ambient temperature. M23C6 carbides were identified as the primary precipitates, while a smaller amount of M6C was also observed. The aging effects were quantified in several aspects: (1) macroscopic tensile properties, (2) volume fraction of the M23C6 Phase, (3) the lattice strain evolution of both the matrix and the M23C6 precipitates, and (4) the dislocation density evolution during plastic deformation. The property-microstructure relationship is described with a focus on the evolution of the M23C6 phase. For aging up to 3000 h, the yield strength (YS) and ultimate tensile strength (UTS) showed little variation, with average values being 454 MPa and 787 MPa, respectively. At 10,000 h, the YS and UTS reduced to 380 MPa and 720 MPa, respectively. The reduction in YS and UTS is mainly due to the coarsening of the M23C6 Precipitates. After long term aging, the volume fraction of the M23C6 phase reached a plateau and its maximum internal stress was reduced, implying that under large internal stresses the carbides were more susceptible to fracture or decohesion from the matrix. Finally, the calculated dislocation densities were in good agreement with transmission electron microscopy (TEM) measurements. The square roots of the dislocation densities and the true stresses displayed typical linear behavior and no significant change was observed in the alloys in different aging conditions. (C) 2015 Elsevier B.V. All rights reserved.

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