Effects of internal hydrogen on the vacancy loop formation probability in Al

Conference · Sun Apr 01 04:00:00 EDT 1990

OSTI ID:7144614

Bui, T X; Sirois, E; Robertson, I M ^[1]; Kirk, M A ^[2]

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1. Illinois Univ., Urbana, IL (USA). Dept. of Materials Science and Engineering
2. Argonne National Lab., IL (USA)

The effect of internal hydrogen on the formation of vacancy dislocation loops from heavy-ion generated displacement cascades in Al has been investigated. Samples of high-purity aluminum and aluminum containing 900 and 1300 appM of hydrogen were irradiated at room temperature with 50 keV Kr+ ions. The ion dose rate was typically 2 {times} 10{sup 10}ions cm{sup {minus}2} sec{sup {minus}1} and the ion dose was between 10{sup 11} and 10{sup 13} ion cm{sup {minus}2}. Under these irradiation conditions, dislocation loops were observed in all compositions, although the formation probability was relatively low (less than 10 percent of the displacement cascades produced a vacancy loop). The loop formation probability was further reduced by the presence of hydrogen. No difference in the geometry or the size of the loops created in the hydrogen free and hydrogen charged samples was found. These results are difficult to interpret, and the explanation may lie in the distribution and form of the hydrogen. To account for the large hydrogen concentrations and from calculations of the energy associated with hydrogen entry into aluminum, it has been suggested that the hydrogen enters the aluminum lattice with an accompanying vacancy. This will create hydrogen-vacancy complexes in the material; two dimensional complexes have been detected in the hydrogen-charged, but unirradiated, samples by the small-angle x-ray scattering technique. The possibility of these complexes trapping the vacancies produced by the cascade process exists thus lowering the formation probability. However, such a mechanism must occur within the lifetime of the cascade. Alternatively, if a displacement cascade overlaps with the hydrogen-vacancy complexes, the lower atomic density of the region will result in an increase in the cascade volume (decrease in the local vacancy concentration) which will also reduce the loop formation probability.

• Research Organization: Argonne National Lab., IL (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-31109-ENG-38; AC02-76ER01198
• OSTI ID: 7144614
• Report Number(s): CONF-900623-8; ON: DE90011114
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360106* -- Metals & Alloys-- Radiation Effects
ALUMINIUM
CASCADE THEORY
CHARGED PARTICLES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DISLOCATIONS
ELECTRON MICROSCOPY
ELEMENTS
HYDROGEN
IONS
IRRADIATION
KRYPTON IONS
LINE DEFECTS
METALS
MICROSCOPY
NONMETALS
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
SAMPLE PREPARATION