Experiments in high voltage electron microscopy. Progress report, October 31, 1976--August 1977

Technical Report · Fri Jul 01 04:00:00 EDT 1977

DOI:https://doi.org/10.2172/7295247· OSTI ID:7295247

Mitchell, T. E.; Hobbs, L. W.; Howitt, D. G.; Barnard, R.; Ro, H.

High voltage electron microscopy (HVEM) is being used to study the effects of irradiation on a variety of materials. The vacancies and interstitials produced by displacement can aggregate to form dislocation loops and voids, annihilate at sinks, or enhance various diffusion processes such as precipitation and recrystallization. Threshold displacement energies, E/sub d/, have been determined for a number of fcc, bcc and hcp metals and for various oxides. In MgO, E/sub d/ is less along (100) than (110); also, E/sub d/ decreases with increasing temperature, possibly due to thermally activated escape of interstitials from recombination volumes or softening of saddle points. The effects of electron irradiation on precipitation in Al--Cu, Al--Si and Ni--Al alloys have been investigated. Precipitation respectively of theta', Si and ..gamma..' is enhanced and growth rates are explicable in terms of theories of radiation-enhanced diffusion, with D/sub rad/ approx. 10/sup -15/ cm/sup 2/ sec/sup -1/. In oxides, damage gives rise to interstitial dislocation loop nucleation and growth in all cases, perfect (110) loops in MgO faulted basal and prismatic loops in Al/sub 2/O/sub 3/. Quantitative analysis of loop growth rates in MgO gives a migration energy of 3.3 eV for anion vacancies. Other radiation effects include sublimation of MgO and decomposition of MgAl/sub 2/O/sub 4/ and Mg/sub 2/SiO/sub 4/ into MgO plus other phases.

• Research Organization: Case Western Reserve Univ., Cleveland, Ohio (USA). Dept. of Metallurgy and Materials Science
• Sponsoring Organization: US Energy Research and Development Administration (ERDA)
• DOE Contract Number: EY-76-S-02-2119
• OSTI ID: 7295247
• Report Number(s): COO-2119-19
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360106* -- Metals & Alloys-- Radiation Effects
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
BINARY ALLOY SYSTEMS
COPPER ALLOYS
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
LEPTONS
MEV RANGE
MEV RANGE 01-10
NICKEL ALLOYS
PHYSICAL RADIATION EFFECTS
PRECIPITATION
RADIATION EFFECTS
SEPARATION PROCESSES
SILICON ALLOYS