Simulation of Neutron Irradiation Damage in Stainless Steel by Cold Rolling
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JMEPEG https://doi.org/10.1007/s11665-020-05166-1
Simulation of Neutron Irradiation Damage in Stainless Steel by Cold Rolling C.R. Arganis-Jua´rez, T.L. Rosas-Flores, A.K. Arias-Alca´ntara, N.F. Garza-Montes-de-Oca, and R. Cola´s (Submitted April 25, 2020; in revised form August 27, 2020; Accepted: 23 September 2020) Simulation of irradiation damage in a stainless-steel type 304L was studied by means of cold rolled samples that were then subjected to different annealing cycles to assess their recovery and compare it with the behavior observed in annealed neutron irradiated samples. Changes in hardness as a function of time and temperature were used to compute the activation energy associated with the recovery in hardness; such value coincided with those reported in literature for irradiated samples. The study was coupled with the evaluation of the degree of sensitization in the cold-rolled and annealed samples by means of the electrochemical potentiokinetic reactivation technique. Annealing the cold-rolled samples for 5 h at 500 °C resulted in the optimum treatment for reducing the hardness as it does not sensitize the steel. Keywords
annealing, irradiation damage, mechanical working, sensitization, stainless steel
1. Introduction Structural components located near the core of light water reactors (LWR) are exposed to intense radiation fields that cause neutron irradiation damage affecting their properties and, in some cases, resulting in the degradation of their integrity (Ref 1). Among the different phenomena that affect structural components made from austenitic stainless steels are swelling, sensitization and irradiation-assisted stress corrosion cracking (IASCC) (Ref 2-5), which is associated with the increase in cracking susceptibility and crack growth rate at the high water temperatures that the structural components should withstand. IASCC has become more prominent with the increase in neutron fluence, and it is a concern in LWR in operation for over 60 years. Radiation hardening is caused by the interaction of high energy radiation with the metal lattice; neutrons are more effective than gamma radiation. In the simplest representation, a neutron collides with the metal lattice and displaces the metallic atom from its original location, creating a vacancy and an interstitial, i.e., the metal atom is jammed into the lattice as a new location. Damage is enhanced as the primary knock-on atom (PKA) collides with other metallic atoms to enlarge the damaged zone, as a higher number of vacancies and interstitials are formed, although often a significant fraction of them
recombine and coalesce to form vacancy and interstitial loops of nanometric dimensions that are very effective barriers to dislocation motion (Ref 5). However, the first dislocations that move through a highly irradiated structure tend to clear the fine barriers, producing localized work softening and creating a highly preferential channel for subsequent dislocation motion (known as dislocation channeling). The increase in yield strength and the ten
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