ISSN:1042-0150    

DOI:10.1080/10420159008213050

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The Fusion Materials Programme of the European Communities is largely focused on the next step in the European strategy towards fusion energy development, i.e. on NET, the Next European Torus. The main objectives and operating conditions of NET are therefore first briefly presented. Consequently a review is given of the present status of our knowledge regarding the main metallic structural materials envisaged for the first wall/blanket and for the divertor plates. Attention is further paid to the need for longer term research and development towards low activation structural materials to be used in a post-NET Demonstration Reactor. Finally a survey is presented of the current European Fusion Technology Programme devoted to the various candidate structural and protection materials for fusion devices.

ISSN:1042-0150    

DOI:10.1080/10420159008213051

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

It is the purpose of this paper to discuss the influence of primary recoil spectra on microstructural evolution in irradiated metals. In particular the consequences are explored of the recoil sensitivity of a transient population of vacancy loops formed directly in the vacancy rich cores of cascades on the evolution of the damage at low and high doses. The importance of the defect motion in the thermal spoke created by the displacement cascade is emphasised, and the dependence of vacancy loop production on material and irradiation parameters is described. The influence of vacancy loops on void swelling and irradiation hardening is discussed by reference to the predictions of the rate theory approach to physical modelling of the microstructural evolution. Finally, the consequences of high energy recoils on preexisting features of the microstructure is reviewed.

ISSN:1042-0150    

DOI:10.1080/10420159008213052

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This is a review of a series of experiments on formation, annihilation, structure or behaviour of cascade defects byin-situobservation using a 400 kV heavy ion accelerator/200 kV electron microscope link facility at the University of Tokyo. Most of the results described here are obtained in gold. The experiments take advantage of the high mobility of interstitials in gold and of the strong effect of surface sinks on the thin foil specimens, which reveal vacancy properties rather distinctively. The temperature of thein-situobservations ranges from 120 to 800 K.

ISSN:1042-0150    

DOI:10.1080/10420159008213053

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper summarizes recent progress in the understanding of energetic displacement cascades in metals achieved with the molecular-dynamics (MD) simulation technique. Recoil events with primary-knock-on-atom (PKA) energies up to 5 keV were simulated in Cu and Ni. The initial development of displacement cascades was similar in both metals, with replacement collision sequences providing the most efficient mechanism for the separation of interstitials and vacancies. The thermal-spike behavior in these metals, however, is quite different; Cu cascades are characterized by lower defect production and greater atomic disordering than those in Ni. The thermal spike significantly influences various other properties of cascades, such as total defect production and defect clustering.

ISSN:1042-0150    

DOI:10.1080/10420159008213054

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A methodology developed for modeling many aspects of high energy displacement cascades with molecular level computer simulations is reviewed. The initial damage state is modeled in the binary collision approximation (using the MARLOWE computer code), and the subsequent disposition of the defects within a cascade is modeled with a Monte Carlo annealing simulation (the ALSOME code). There are few adjustable parameters, and none are set to physically unreasonable values. The basic configurations of the simulated high energy cascades in copper, i.e., the number, size and shape of damage regions, compare well with observations, as do the measured numbers of residual defects and the fractions of freely migrating defects. The success of these simulations is somewhat remarkable, given the relatively simple models of defects and their interactions that are employed. The reason for this success is that the behavior of the defects is very strongly influenced by their initial spatial distributions, which the binary collision approximation adequately models. The MARLOWE/ALSOME system, with input from molecular dynamics and experiments, provides a framework for investigating the influence of high energy cascades on microstructure evolution.

ISSN:1042-0150    

DOI:10.1080/10420159008213055

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An analysis of cascade and subcascade formation in fcc metals by D-T fusion neutron irradiation is made by fitting the experimentally observed distribution of cascade zone size and number of subcascades to the calculated primary recoil energy spectrum. The analysis is made by categorizing subcascades into closely space (Ag, Au) and widely separated (Cu, Ni). The energy subdivided in subcascades is estimated. The estimated energy density in a subcascade is as high as several tens of eV/atom, which is high enough to raise the local temperature far beyond the melting temperature. A discussion is made on the reactions during cascade cooling, suggesting the inadequacy of the conventional radiation damage parameter of DPA. The existence of impact effects from other cascades to reveal the cascade collision induced invisible vacancies as visible vacancy clusters is concluded. A kinetics type of analysis is made on the microstructure evolution by the impact effect, and the sphere of influence of the impact is estimated for each material.

ISSN:1042-0150    

DOI:10.1080/10420159008213056

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

For quantitative predictions and comparisons of microstructures that evolve during exposure to different radiation environments at elevated temperature one needs to develop methods that go beyond those based on the number of displacements per atom. The number of freely migrating defects that contribute to the microstructural development is far less than the total number of defects produced, as has been recognized for some time from measurements of radiation-induced segregation and of radiation-enhanced diffusion. Defect production in various neutron and ion irradiation environments is discussed in light of this fact. A method to calculate the fraction of freely migrating defects from the cluster size distribution of defects produced in cascades is suggested. The results are in good agreement with available data.

ISSN:1042-0150    

DOI:10.1080/10420159008213057

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Changes in dimensions, mechanical properties and chemical composition due to irradiation by different particles at elevated temperatures are compared on the basis of atomic displacements derived from low temperature resistivity damage rates. The available data on void swelling, irradiation creep and room temperature hardening correlate reasonably well on this basis. The correlation seems poor for hardening at high temperatures and even worse for fracture properties and chemical effects (solute segregation, precipitate growth). The results are discussed in terms of the basic damage processes.

ISSN:1042-0150    

DOI:10.1080/10420159008213058

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The free defect survival ratio is calculated by “cascade-annealing” computer simulation using MARLOWE and modified DAIQUIRI codes in various cases of PKA spectra. The number of subcascades is calculated by “cut-off” calculation using MARLOWE. The adequacy of these methods is checked by comparing the results with experiments (surface segregation measurements and TEM cascade defect observations). The correlation using the weighted average recoil energy as a parameter shows that the saturation of the free defect survival ratio at high PKA energies has a close relation to the cascade splitting into subcascades.

ISSN:1042-0150    

DOI:10.1080/10420159008213059

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor