Investigation of Dual-Beam-Implanted Oxide-Dispersed-Strengthened FeCrAl Alloy by Positron Annihilation Spectroscopy

2012 ◽  
Vol 331 ◽  
pp. 149-163 ◽  
Author(s):  
Reinhard Kögler ◽  
Wolfgang Anwand ◽  
Asta Richter ◽  
Maik Butterling ◽  
A. Mücklich ◽  
...  

Oxide-dispersion-strengthened (ODS) FeCrAl steel is a class with promising materials to be applied for future nuclear applications. However, radiation damage, especially the formation of vacancy clusters or gas-filled bubbles, may result in hardness increase and the loss of ductility. Positron annihilation spectroscopy (PAS) is demonstrated to be a very useful and non-destructive analysis method to detect and to determine open volume defects of sub-nm size in ODS alloy. Synchronized dual beam implantation of Fe and He ions is performed to simulate the radiation damage caused by (n, α) reactions and to avoid induced activation. For room temperature implantation, i.e. without significant point defect recombination, the differences in the defect formation are shown by comparison between irradiation of ODS alloy and pure Fe bulk. The open volume defects created in ODS alloy are vacancy clusters closely connected with dispersed Y oxide nanoparticles. Their profiles are in reasonable qualitative agreement with the hardness profiles, indicating a relationship between sub-nm vacancy clusters or He bubbles and the hardness of the material. In heat-treated ODS alloy, containing larger vacancy clusters, the radiation induced hardness increase is more distinctive than for as-received ODS alloy. For irradiation at a moderately enhanced temperature of 300°C open volume defects are drastically reduced. The few remaining defects are vacancy clusters of the same type as in as-received ODS alloy. Close to the surface the open volume defects completely disappear. These results are in agreement with the hardness measurements showing little hardness increase in this case. The suitability of ODS-based materials for nuclear applications was verified.

2009 ◽  
Vol 94 (6) ◽  
pp. 061910 ◽  
Author(s):  
M. J. Wang ◽  
L. Yuan ◽  
C. C. Cheng ◽  
C. D. Beling ◽  
K. J. Chen

2013 ◽  
Vol 442 (1-3) ◽  
pp. S856-S860 ◽  
Author(s):  
H. Tsuchida ◽  
T. Iwai ◽  
M. Awano ◽  
N. Oshima ◽  
R. Suzuki ◽  
...  

2021 ◽  
Vol 1024 ◽  
pp. 1-12
Author(s):  
Vladimir Krsjak

The well-known and often acceptable radiation tolerance of ferritic/martensitic (f/m) steels can be severely diminished when neutron irradiation is accompanied by the production of helium. The presence of helium in the irradiated materials changes the kinetics of the nucleation, recombination, and clustering of the radiation-induced defects. High production rates of helium may lead to a non-negligible volumetric bubble swelling at relatively low temperatures. Extrapolation of the knowledge gained from neutron irradiation experiments to fusion or spallation environments is additionally complicated due to the unknown and comprehensive effects of dpa rate, temperature, the presence of sinks in the crystal lattice and others. To improve the understanding of the microstructure and irradiation parameters effects, close attention must be paid to the early stages of the radiation damage. It is expected that the pre-existing vacancy-type defects, attributed to lattice distortion at the grain/subgrain boundaries and oxide-matrix interfaces, are effective sinks for primary defects and helium, i.e. they control the formation and growth of helium-vacancy agglomerations. This early-stage radiation damage, however, cannot be captured by conventional transmission electron microscopy, and thus other experimental techniques are called for. One of the most perspective experimental approaches to investigate small vacancy-type defects, with a high sensitivity to confined helium, is to utilize positron annihilation spectroscopy (PAS). In particular, two spectroscopy techniques, positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy (DBS) of the annihilation line, can be beneficially used for the characterization of helium-vacancy clusters. This paper reviews the recent positron annihilation spectroscopy characterization of various irradiation experiments involving helium. Mainly two types of irradiation experiments are addressed, helium implantation and spallation neutron source irradiation experiments. Discussion is aimed at the potential of PAS in the early-stage formation of helium bubbles and the investigation of the effects of irradiation parameters in defect production and accumulation.


1998 ◽  
Vol 507 ◽  
Author(s):  
X. Zou ◽  
Y. C. Chan ◽  
D. P. Webb ◽  
Y. W. Lam ◽  
S. H. Lin ◽  
...  

ABSTRACTWe show how positron annihilation can distinguish vacancies in undoped hydrogenated amorphous silicon by performing Variable Energy Positron Annihilation Spectroscopy experiments before and after light soaking. We find that vacancy clusters, di-vacancies and a new type of single vacancies are created in undoped as-grown a-Si:H thin film by light illumination. The fact that the vacancy clusters are eliminated by the thermal annealing suggests that the Staebler-Wronski effect is closely related to vacancy clusters in a-Si:H material. The creation of vacancy clusters and redistribution of di-vacancies and even single vacancies probably result in photo-induced structural changes in this material.


2013 ◽  
Vol 102 (15) ◽  
pp. 151901 ◽  
Author(s):  
P. Parz ◽  
B. Fuchsbichler ◽  
S. Koller ◽  
B. Bitschnau ◽  
F.-A. Mautner ◽  
...  

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