The Effect of Bulk Composition on Swelling and Radiation-Induced Segregation in Austenitic Alloys
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MRS 2000 Fall Meeting Symposium R: Microstructural Processes in Irradiated Materials THE EFFECT OF BULK COMPOSITION ON SWELLING AND RADIATION-INDUCED SEGREGATION IN AUSTENITIC ALLOYS
T. R. Allen , J. I. Cole, and N. L. Dietz, Argonne National Laboratory-West Y. Wang and G. S. Was, University of Michigan E. A. Kenik, Oak Ridge National Laboratory
Abstract Changes in bulk composition are known to affect both radiation-induced segregation and microstructural development, including void swelling in austenitic stainless steel. In this work, three alloys (designations corresponding to wt%) have been studied: Fe-18Cr-8Ni alloy (bulk composition corresponding to 304 stainless steel), Fe-18Cr-40Ni (bulk composition corresponding to 330 stainless steel), and Fe-16Cr-13Ni (bulk composition corresponding to 316 stainless steel). Following irradiation with high-energy protons, the change in hardness and microstructure (void size distribution and grain boundary composition) due to irradiation was investigated. Increasing the bulk nickel concentration decreases void swelling, increases matrix hardening, and increases grain boundary chromium depletion and nickel enrichment. The analysis shows that decreases in lattice parameter and shear modulus due to radiationinduced segregation (RIS) correlate with decreased void swelling and a decreased susceptibility to irradiation assisted stress corrosion cracking (IASCC). Traditional thinking on IASCC assumed RIS was a contributing factor to cracking. It may, however, be that properly controlled RIS can be used to mitigating cracking.
Introduction This study analyzes the effect of alloy composition on void swelling, radiation-induced grain boundary segregation, and hardening in a series of Fe-Cr-Ni alloys. An Fe-18Cr-8Ni alloy (composition corresponding to 304 stainless steel) is used as the reference alloy for this project. AISI type 304 stainless steel is known to be susceptible to both swelling and irradiation assisted stress corrosion cracking (IASCC), where IASCC may be caused by grain boundary chromium depletion during irradiation. Alloying additions are made to improve the swelling and grain boundary segregation resistance relative to 304 stainless steel. Two compositions were studied in addition to the base alloy: Fe-18Cr-40Ni (corresponding to 330 stainless steel) and Fe-16Cr-13Ni (corresponding to 316 stainless steel). The Fe-18Cr40Ni-alloy is studied to measure grain boundary segregation in an alloy that exhibits excellent swelling resistance. The Fe-16Cr-13Ni alloy is studied to determine the effect of major element composition change between 304 and 316 stainless steel. AISI 316 is more swelling resistant [1] and more resistant to IASCC [2] than 304. R3.12.1
Experiment Table 1 provides the compositions of each alloy. Each alloy was cold-worked and then underwent a recrystallization anneal to obtain an average grain size of around 20 microns. Twenty-micron grains were desired because the range of damage in the proton beam used to irradiate samples is approximately forty mic
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