Abstract
This work presents a methodology combining SEM, EDS, conventional EBSD, and transmission-EBSD to analyse a recrystallised Zircaloy-4 sheet and cold-worked stress-relieved (CWSR) Zircaloy-4 cladding in unprecedented detail. Second-phase precipitates (SPPs) in Zircaloy-4 specimens were revealed after chemical polishing using a solution containing hydrofluoric acid (HF). Pitting corrosion of Zircaloy-4 specimens was revealed after electropolishing using an electrolyte containing HClO4. A zirconium coupon without SPPs was used to confirm the chemical response of SPPs on surface morphology. Intrinsic features of cold-worked Zircaloy-4 such as relatively small grain sizes, high dislocation density, and complex microstructure make it significantly more difficult to collect excellent EBSD results compared to recrystallised Zircaloy-4. The fine hydride structure of as-hydrided CWSR Zircaloy-4 cladding further increases the level of challenge on EBSD analysis. Lay description: We present a methodology combining multiple microscopic methods to analyse a recrystallised Zircaloy-4 sheet and cold-worked stress-relieved (CWSR) Zircaloy-4 cladding, important alloys of structural materials widely used in nuclear application, and emphasis on the challenge of acquiring a satisfactory electron backscatter diffraction (EBSD) result of CWSR Zircaloy-4 cladding material in great details. EBSD is a powerful technique to characterise the crystallographic distribution and lattice type of conductive crystalline materials, especially for a highly textured material like CWSR Zircaloy-4 alloy. However, zirconium alloys are known to be one of the most difficult materials to prepare for EBSD characterisation. We point out that the configuration of the microstructure of the specimen cause the challenge in the EBSD sample preparations. Moreover, the occurrence of tiny zirconium hydride precipitates in Zircaloy-4 increases the difficulty. We believe that the information of the EBSD sample preparation related results in this paper can provide researchers and scientists in this community a useful reference to speed up the EBSD sample preparation of CWSR Zircaloy-4 cladding material and to expect the corresponding EBSD results.
| Original language | English |
|---|---|
| Pages (from-to) | 25-34 |
| Number of pages | 10 |
| Journal | Journal of Microscopy |
| Volume | 272 |
| Issue number | 1 |
| DOIs | |
| State | Published - Oct 2018 |
Funding
This work was supported by the U.S. Department of Energy Nuclear Energy Fuel Aging in Storage and Transportation IRP under Grant Number IRP-11-5352, IRP-11-3278 and by the U.S. Department of Energy Accident Tolerant Fuel IRP under Contract Number IRP-12-4728. The help during the hydrogenation and the concentration measurement by Institute of Nuclear Energy Research in Taiwan is gratefully acknowledged. The SEM/ EDS/ EBSD/ t-EBSD experiments were carried out in part at the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which is partially supported by the U.S. Department of Energy under grants DEFG02-07ER46453 and DE-FG02-07ER46471. The anonymous reviewer contribution to this paper is greatly acknowledged. Fundinginformation:FuelAginginStorageandTransportationIRP,USDepartment of Energy, Grant Number: IRP-11-5352 and IRP-11-3278; Accident Tolerant Fuel IRP, US Department of Energy, Grant Number: IRP-12-4728 Correspondence to: Kuan-Che Lan, Department of Nuclear, Plasma and Radiological Engineering, University of Illinois, Urbana, IL 61801, USA. Tel: +1-608-556-9518; fax: +1-217-333-2906; e-mail: [email protected]
Keywords
- CWSR Zircaloy-4
- EBSD
- electropolishing
- grain size
- zirconium hydride