Studies of high dpa ion beam irradiation effects on fcc AA-6061 and fcc-bcc duplex steel 2205: micromechanical modelling and nano-indentation examination of hardness variations
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Date
2015-05-10
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Karlsruhe Institute of Technology
Abstract
The irradiation effects of high dpa and the ramification on the engineering assessment of reactor components in GEN IV systems is of considerable interest. Most polycrystalline metallic materials derive their strengths from the interactions of dislocations with defects such as solid solution alloying elements, interstitial elements, other dislocations, grain boundaries and sub-microscopic precipitates. Irradiation of metals and alloys at temperatures below those that anneal their defects typically produces pronounced radiation hardening, this is investigated herein to better understand the application of complex alloys in future reactor systems. .
The current study focuses on ion beam irradiation of AA6061 and Duplex steel 2205, utilising the ANATRES Accelerator at ANSTO with 12 MeV Au+5 ions used as the irradiating ions. To induce a 100 dpa damage, often cited as the operating level of GEN IV reactor, heavy Au+5 ions are necessary as self-ion irradiation would fail to induce the required damage. The main attribute of ion irradiation is the rapid accumulation of end of life doses over a short duration.. Conversley, neutron irradiation experiments in thermal test reactors may accumulate damage at a rate of 3–5 dpa year, e.g. the ANSTO OPAL reactor with 20 MW is capable of 100 MeV with reactor face neutron thermal flux of 4.0E10 n/cm2/s thus resulting in a less than optimal 2 dpa per year.
A key question still exits between the complementarity of neutron and ion irradiation with respect to the nature of damage, size, density and distribution of dislocation loops; black dots; and the extent of the dislocation networks. Although the same number of displacements can be produced using ion irradiation, there are differences in spatial defect distribution between thes e teh two. The post-irradiation measurements in effect quantify the final state of damage and the neutron-ion equivalence without an evaluation of the damage path.
The simulation code Stopping and Range of Ions in Materials (SRIM) is used to model the irradiation process and compute the initial required experimental flux. Post irradiation studies of the micromechanical behaviour are done through nano-indentation (to a depth of 300 nm) using a diamond Berkovich tip. This allows for estimates of moduli and relative estimates of the strengths and hardening of individual phases and individual grains within a multiphase alloy. The results show a marked increase in the hardening of AA 6061 with a more modest increase in the Duplex steel 2205. Coupling these results to micromechanical FEA and crystal plasticity modelling, the authors hope to better describe the role of multi-scale modelling in complementing micromechanical testing and the extrapolation of results for engineering assessment.
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Keywords
Irradiation, Atomic displacements, Reactor components, Solid solutions, Hardening, Annealing
Citation
Saleh, M., Munroe, P., Short, K., & Edwards, L. (2015). Studies of high dpa ion beam irradiation effects on fcc AA-6061 and fcc-bcc duplex steel 2205: micromechanical modelling and nano-indentation examination of hardness variations. Paper presented at the ICM 12 - 12th International Conference on the Mechanical Behavior of Materials, 10-14 May 2015, Karlsruhe, Germany (pp. 283). Retrieved from: https://www.iam.kit.edu/downloads/Book_of_Abstracts_ICM12.pdf