Positron Annihilation Study of Neutron-Irradiated Nuclear Reactor Pressure Vessel Steels and their Model Alloy: Effect of Purity on the Post-Irradiation Annealing Behavior

2012 ◽  
Vol 733 ◽  
pp. 257-263 ◽  
Author(s):  
Akira Kuramoto ◽  
Yasuyoshi Nagai ◽  
T. Toyama ◽  
T. Takeuchi ◽  
M. Hasegawa
Keyword(s):  
Positron Annihilation ◽  
First Generation ◽  
Nuclear Reactor ◽  
Positron Annihilation Spectroscopy ◽  
Atom Probe ◽  
Model Alloy ◽  
Annealing Behavior ◽  
Post Irradiation ◽  
Alloy Effect ◽  
Positron Annihilation Study

Post-irradiation annealing (PIA) behavior of irradiation-induced microstructural changes and hardening of two kind of A533B (first generation (1stGENS: 0.16 wt.% Cu) and second generation (2ndGENS: 0.04 wt.% Cu)) steels after neutron-irradiation of 3.9 × 1019 n cm–2 at 290 °C has been studied by positron annihilation spectroscopy, atom probe tomography and Vickers microhardness measurements. In the 1stGENS, clear two recovery stages are observed: (i) as-irradiated state to 450 °C and (ii) 450 to 600 °C. The first stage is due to annealing out of the most of irradiation-induced vacancy-related defects (VRDs), and the second stage corresponds to dissolving irradiation-induced Cu-rich solute nano-clusters (CRSCs). The experimental hardening is almost twice of the hardening due to the CRSCs estimated by Russell-Brown model below 350 °C, but almost the same as the estimation from 400 to 550 °C. In the 2ndGENS, the VRDs and non-Cu-rich solute nano-clusters (NCRSCs) recover at 450 °C. No CRSC has been formed even in all the annealing process. The experimental hardening is almost twice of the hardening estimated due to the NCRSCs by Russell-Brown model below 400 °C.

On the Behavior of Yttria/Yttrium during Mechanical Alloying of a Fe - Y2O3 Model Alloy System

2014 ◽  
Vol 922 ◽  
pp. 598-603
Author(s):  
Gerald Ressel ◽  
Peter Parz ◽  
Alexander Fian ◽  
David Holec ◽  
Sophie Primig ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Positron Annihilation ◽  
Photoelectron Spectroscopy ◽  
Atom Probe Tomography ◽  
Elevated Temperatures ◽  
Positron Annihilation Spectroscopy ◽  
Atom Probe ◽  
Model Alloy ◽  
High Temperature Strength ◽  
X Ray

Mechanical alloying (MA) is an established way to prepare nanocrystalline materials and metastable solutions of materials, which normally have no mutual solubility. This is also the case for oxide dispersion strengthened (ODS) steels with improved mechanical properties at elevated temperatures. It is known that a small addition of yttria (Y2O3) has a beneficial effect on high temperature strength and reduces the creep rate in mechanically alloyed ferritic steels by about six orders of magnitude. In this work we present an experimental study using atom probe tomography, X-ray photoelectron spectroscopy, and positron annihilation spectroscopy combined with first principles modeling focusing on the distribution and behavior of yttria in pure iron prepared by mechanical alloying. Atom probe tomography and X-ray photoelectron spectroscopy measurements as well as positron annihilation spectroscopy conducted on powder particles directly after milling have revealed that a predominantly fraction of the yttria powder dissolves in the iron matrix and Y atoms occupy convenient positions, such as vacancies or dislocations. This is supported by ab initio calculations demonstrating that the formation energy for Y substitutional defects in bcc-Fe is significantly lower in the close neighborhood of vacancies.

701 Surveillance Test Specimens of Nuclear Reactor Pressure Vessel Steels analyzed by 3D Atom Probe and Positron Annihilation

2006 ◽  
Vol 2006 (0) ◽  
pp. 379-380
Author(s):  
Yasuyoshi NAGAI ◽  
Takeshi TOYAMA ◽  
Zheng TANG ◽  
Masayuki HASEGAWA ◽  
Abderrahim Almazouzi ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Pressure Vessel ◽  
Nuclear Reactor ◽  
Atom Probe ◽  
Reactor Pressure Vessel ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Characterization of Atomic Defects and Their Aggregates Using Positron Annihilation Spectroscopy

1984 ◽  
Vol 41 ◽  
Author(s):  
R. W. Siegel ◽  
M. J. Fluss ◽  
L. C. Smedskjaer
Keyword(s):  
Electronic Structure ◽  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Molecular Solids ◽  
Microstructure Development ◽  
Post Irradiation ◽  
Defect Sites ◽  
Atomic And Electronic Structure

AbstractPositrons localize in trapped states at a variety of defect sites in solids, from which they subsequently annihilate with unique observable characteristics. As such, the positron is a valuable probe for the study of these defects. Positron annihilation spectroscopy (PAS) has made significant contributions in recent years to the determination of atomic defect properties in metals and alloys, and in molecular solids as well. It has also been used extensively in the monitoring and characterization of vacancy-like microstructure development, as occurs during post-irradiation annealing. The characterization of defects using PAS is selectively reviewed and some possibilities for using the positron as a localized probe of the atomic and electronic structure of atomic defects and their aggregates are discussed.

scholarly journals A positron annihilation study of defect accumulation in phosphorus- and titanium-alloyed austenitic stainless steels under electron irradiation at room temperature

2020 ◽  
pp. 27-34
Author(s):  
D. A. Perminov ◽  
Keyword(s):  
Positron Annihilation ◽  
Electron Irradiation ◽  
Stainless Steels ◽  
Room Temperature ◽  
Austenitic Stainless Steels ◽  
Positron Annihilation Spectroscopy ◽  
High Concentration ◽  
Noticeable Effect ◽  
Vacancy Defects ◽  
Positron Annihilation Study

The effect of phosphorus and titanium additions on the accumulation of vacancy defects in Cr16Ni15Mo3 austenitic stainless steels under electron irradiation at room temperature is studied by positron annihilation spectroscopy. It is shown that, at this temperature, phosphorus has no noticeable effect on the accumulation of vacancy defects. This is due to the low mobility of vacancies and the low concentration of impurities. Titanium, due to its high concentration, enhances the accumulation of vacancy defects during irradiation, but this effect is weak.

Positron annihilation study of post-irradiation annealing of defects in α-irradiated molybdenum

1985 ◽  
Vol 52 (2) ◽  
pp. 255-266 ◽  
Author(s):  
S. V. Naidu ◽  
A. Sen Gupta ◽  
R. Roy ◽  
P. Sen ◽  
R. K. Bhandari
Keyword(s):  
Positron Annihilation ◽  
Post Irradiation ◽  
Positron Annihilation Study
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