SYMPOSIA PAPER Published: 01 January 1982
STP34369S

Irradiation Embrittlement in Some Austenitic Superalloys

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The nature of the irradiation embrittlement phenomenon in selected austenitic superalloys was evaluated in tubular specimens compression tested at elevated temperatures. Materials included the commercial alloys Inconel 706 and Nimonic PE-16 and two experimental alloys. All are precipitation hardenable and were irradiated from 2.8 to 7.1 × 1022 n/cm2 (E>0.1MeV). The tests revealed marked ductility losses in all alloys, the most severe embrittlement occurring at 110°C above the temperature at which the materials were irradiated. In some instances, zero ductility was recorded. The testing further revealed that short-term post-irradiation heat treatments produced moderate to high levels of ductility recovery without significant losses in strength.

Extensive scanning and transmission electron microscopy examinations have indicated that the low ductility behavior is associated with intergranular fracture and the copious precipitation of γ′ along or adjacent to grain boundaries. Based upon these results it is concluded that the principal cause of embrittlement in these alloys is the precipitation of γ′ along grain boundaries during irradiation. The segregation of silicon in addition to titanium and aluminum is considered a major factor in the embrittlement mechanism.

Author Information

Vaidyanathan, S
Advanced Reactor Systems Department, General Electric Co., Sunnyvale, California
Lauritzen, T
Advanced Reactor Systems Department, General Electric Co., Sunnyvale, California
Bell, WL
Advanced Reactor Systems Department, Vallecitos Nuclear Center, Pleasanton, California
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Details
Developed by Committee: E10
Pages: 619–635
DOI: 10.1520/STP34369S
ISBN-EB: 978-0-8031-4846-8
ISBN-13: 978-0-8031-0753-3