In situ studies of amorphization of the GeAl and SiAl systems induced by 1 MeV electron irradiation

X. W. Lin*, D. N. Seidman, P. R. Okamoto

*Corresponding author for this work

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Abstract

GeAl and SiAl bilayer specimens, and also A1-2.3at.%Ge two-phase alloy specimens, were irradiated in situ with 1 MeV electrons at temperatures in the range 10-190 K in a high voltage electron microscope. The Ge precipitates in the Al2.3at.%Ge alloy disappeared completely at a critical fluence (Φc) of approximately 2.4 × 1023 cm-2 (24 displacements per atom (dpa) in Ge and 14 dpa in Al) for specimens irradiated at 10 or 50 K; this is the same value of Φc at which GeAl bilayers are found to contain an amorphous phase. At 10 K an irradiated GeAl bilayer specimen is found to have an amorphous phase at the interface only when a Ge layer faces the incident electron beam, while for a SiAl bilayer specimen amorphization occurs at the interface independent of the direction of the incident beam with respect to a bilayer. For GeAl bilayer specimens Φc is approximately 2.5 × 1023 cm-2 (25 dpa in Ge and 15 dpa in Al). For SiAl bilayers Φc is approximately 3 × 1023 cm-2 (19 dpa in Si and 18 dpa in Al). The temperature dependence of Φc is also studied for a GeAl bilayer specimen. The value of Φc is a constant for T < ≈160 K, and then it increases rapidly with increasing T; Φc becomes immeasurably large (more than 70 dpa in Ge and more than 43 dpa in Al) at a critical temperature of about 190 K. The temperature dependence of the crystalline to amorphous transition is explained in terms of a recoil-implantation mechanism, coupled with a radiation-enhanced monovacancy diffusion mechanism for Ge atoms in Al, and an athermal contribution to Ge diffusion in Al via an electron-beam stimulated monovacancy migration mechanism.

Original languageEnglish (US)
Pages (from-to)389-400
Number of pages12
JournalJournal of Alloys and Compounds
Volume194
Issue number2
DOIs
StatePublished - May 7 1993

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ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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