Landolt-Börnstein - Group III Condensed Matter

Atomic Defects in Metals · 3.3.3 Diffusion

Abstract

This chapter discusses the diffusion of helium atoms in metals. The migration of atoms is characterized by diffusion coefficient D. The results of experimental investigations together with the information obtained from computer simulation suggest three diffusion mechanisms for helium atoms in metals. They are 1) migration via jumps between interstitial sites with an activation energy EM I, 2) migration by the vacancy mechanism which operates in most substitutional alloys, and 3) impeded interstitial migration where a substitutional helium atom dissociates from its vacancy and migrates via interstitial sites until it is trapped again. In materials with a complex microstructure, the effective diffusion coefficients may be either enhanced by "easy" migration paths (e.g. along dislocations or grain boundaries) or reduced by trapping at impurity atoms, solid precipitates and voids or bubbles. Experimental evidence for helium pipe diffusion along dislocations has been obtained by THDS. Apparent migration energies EM eff (in eV) and pre-exponential factors D0 (in m2/s) of helium in various metals such as silver, aluminum, gold, cobalt, iron, magnesium, titanium and vanadium deduced from THDS experiments at high temperatures are tabulated.

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Title
Atomic Defects in Metals · 3.3.3 Diffusion
Book Title
Atomic Defects in Metals
In
3.3 Atomistic properties
Book DOI
10.1007/b37800
Chapter DOI
10.1007/10011948_114
Part of
Landolt-Börnstein - Group III Condensed Matter
Volume
25
Editors
  • H. Ullmaier
Authors
  • H. Ullmaier

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