A phenomenological model for the effect of nanocrystalline microstructure on irradiation-induced amorphization in U{sub 3}Si
- Argonne National Lab., IL (United States). Energy Technology Div.
A rate theory model is formulated wherein amorphous clusters are formed by a damage event. These clusters are considered centers of expansion (CEs), or excess-free-volume zones. Simultaneously, centers of compression (CCs) are created in the material. The CCs are local regions of increased density that travel through the material as an elastic (e.g., acoustic) shock wave. The CEs can be annihilated upon contact with a sufficient number of CCs, to form either a crystallized region indistinguishable from the host material, or a region with a slight disorientation (recrystallized grain). Recrystallized grains grow by the accumulation of additional CCs. Preirradiation of U{sub 3}Si above the critical temperature for amorphization results in the formation of nanometer-size grains. In addition, subsequent reirradiation of these samples in the same ion flux at temperatures below the critical temperature shows that the material has developed a resistance to radiation-induced amorphization (i.e., a higher dose is needed to amorphize preirradiated samples than those that have not been preirradiated). In the model, it is assumed that grain boundaries act as effective sinks for defects, and that enhance defect annihilation is responsible for retarding amorphization below the critical temperature by, for example, preventing a buildup of vacancies adjacent to the grain boundaries. The calculations have been validated against data from ion-irradiation experiments with U{sub 3}Si. For appropriate values of the activation energy of thermal crystallization, the model predicts the evolution of a two phase microstructure consisting of nanocrystalline grains and amorphous clusters.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38; AC05-84OR21400
- OSTI ID:
- 99441
- Report Number(s):
- CONF-941144--; ISBN 1-55899-275-8
- Country of Publication:
- United States
- Language:
- English
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