Unified theoretical analysis of experimental swelling data for irradiated austenitic and ferritic/martensitic alloys
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I.
INTRODUCTION
A U S T E N I T I C and ferritic/martensitic alloys are the leading candidate materials for both fusion and fast fission reactor applications. Radiation damage (swelling, in particular) is known to be a life-limiting phenomenon for long-term service. During the past two decades, a large store of experimental data has been accumulated in international efforts to fully characterize the phenomenon and to provide the information necessary for the development of swelling-resistant alloys. This collection also serves as the largest source of information on which to develop and test mechanistic understanding of the phenomenon. Concomitantly, an extensive theoretical framework has been developed in order to describe and predict swelling and other irradiation phenomena based on fundamental physical concepts. [~,zl The ultimate goal is predictive accuracy under the widest possible variation in conditions. The experimentally observed swelling behavior in alloys varies greatly over the range of conditions explored. This range in conditions includes, for example, variations in irradiation parameters (particles, dose rate, energy), alloy composition, and thermomechanical treatments. The diverse data on the austenitic and ferritic/martensitic alloys therefore provide a demanding test bed for the theory. In the present paper, we outline and expand upon a theoretical approach that we have applied previously. [3-6] We call attention to the special importance of the point defect sink microstructure in determining swelling, over and above the parameters characterizing the intrinsic material properties and irradiation conditions. A wide array of experimental data is interpreted for the first time in a E.H. LEE, Senior Research Staff Member, and L.K. MANSUR, Group Leader, are with the Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831. This paper is based on a presentation made in the symposium "Irradiation-Enhanced Materials Science and Engineering" presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25-29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD. METALLURGICAL TRANSACTIONS A
unified manner within the theoretical framework. The power of the theory both for explaining results and for relating principles on which to design swelling-resistant alloys is demonstrated. II.
THEORETICAL BACKGROUND
During energetic-neutron or charged-particle irradiation, atoms are displaced from their normal lattice sites, forming vacancies and interstitials. These defects are lost by mutual recombination or by absorption at point defect sinks. When vacancies and interstitials are absorbed at sinks in nearly equal numbers, most recombine there as well. The balance of point defect sources and sinks dictates the mean steady-state vacancy (Cv) and interstitial (Ci) concentrations. Clustering of like defects in the form of dislocation loops and cavities also occurs. The cavi
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