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Stubbins, James Zhang, Yang Yan, Huan 2018-09-04T20:31:59Z 2018-09-04T20:31:59Z 2018-04-26 2018-05 Alloy 709, a type of 20Cr-25Ni austenitic stainless steel is studied after thermal aging at 550°C and 650°C. The microstructure is characterized using variety of techniques. The alloy shows excellent thermal stability at its working temperature 550°C, while its microstructure evolves rapidly at 650°C with complex precipitation behaviors. NbX particles are of large amount in as-received material but partially dissolve during thermal aging, showing less stability compared to M23C6 at 650°C. A type of M6C’s variant is found after long-term aging and strongly correlated with M23C6, which could either be the result of a possible transition from M23C6 to M6C, or the dissolution of Nb(C, N). Small amount of Z phase are found to precipitate densely on dislocations and modify the dislocation structure after 3000 hours aging at 650◦C. The results are in good agreement with those of NF709 and further support the idea that the η structure can be stabilized by nitrogen. Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-08-31 without embargo terms The student, Huan Yan, accepted the attached license on 2018-04-25 at 15:08. The student, Huan Yan, submitted this Thesis for approval on 2018-04-25 at 15:33. This Thesis was approved for publication on 2018-04-26 at 09:46. DSpace SAF Submission Ingestion Package generated from Vireo submission #12490 on 2018-08-31 at 17:14:49 Made available in DSpace on 2018-09-04T20:31:59Z (GMT). No. of bitstreams: 2 YAN-THESIS-2018.pdf: 33410784 bytes, checksum: 13126d3958816c65fc560f4a396e36c5 (MD5) LICENSE.txt: 4205 bytes, checksum: 52f66bb0c5dccbfe6490b133ccc06b64 (MD5) Previous issue date: 2018-04-26 application/pdf http://hdl.handle.net/2142/101081 en Copyright 2018 Huan Yan Austenitic Stainless Steel, Thermal Aging, Alloy 709 Microstructure evolution in Alloy 709 at 550 and 650 °C text text Nuclear, Plasma, & Rad Engr Nuclear, Plasma, Radiolgc Engr University of Illinois at Urbana-Champaign Thesis M.S.