Microstructural Characterization of Alloy 709 Plate Materials with Additional Heat Treatment Protocol

Technical Report · Thu Aug 01 04:00:00 EDT 2019

DOI:https://doi.org/10.2172/1601459· OSTI ID:1601459

Sham, T. -L. ^[1]; Zhang, X. ^[1]; Young, G. A. ^[1]

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1. Argonne National Lab. (ANL), Argonne, IL (United States)

This report provides the results on microstructural characterization of the first commercial heat of Alloy 709 plate material which has undergone additional heat treatment protocol. The report is a Level 4 deliverable in FY19 (M4AT-19AN020502012), under the Work Package AT19AN0205201, “A709 Development – ANL.” The study involves thermodynamic-kinetic modeling, heat treating of materials, microhardness testing, x-ray diffraction (XRD) study, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) study. Through thermodynamic-kinetic modeling, it is determined that after an 1100°C solutionizing treatment, heat treating of Alloy 709 at 775°C for 10 hours or at 900°C for 10 hours are candidate recipes for promoting desired microstructural features. Both heat treatments were executed on small samples of the AOD-1100°C condition of the commercial heat of Alloy 709. Micro-hardness tests showed that both treatments increases the hardness of the material. XRD showed that both treatments brings out M23C6 and MX phases, though the 775°C/10h-treatment has more profound effect. The TEM study revealed that similar for both conditions, M23C6 precipitated on grain boundaries and within grain interior. In contrast, after the 775°C/10h treatment, the dislocations are decorated with MX nano particles, while after the 900°C/10h treatment, most of the dislocations are free of MX particles. It is thus determined that the 775°C/10h treatment has a better potential to provide enhanced creep properties by pinning the dislocations with nano particles. Following this study, the 775°C/10h treatment was carried out on a large ESR-1100°C plate at Idaho National Laboratory. Hardness testing and microstructural characterization were performed and compared between the two materials being heated treated under the same protocol. The implication on mechanical properties was briefly discussed.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1601459
• Report Number(s): ANL-ART--170; 158588
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE