Anomalous diffusion in the BCC phases of IVB-metals and their alloys

Conference · · TMS (The Metallurgical Society) Paper Selection; (USA)

OSTI ID:5311103

Herzig, C ^[1]

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1. Univ. of Muenster (Germany, F.R.)

Anomalous fast self-diffusion, resulting in small values of the frequency factor and the activation energy in the temperature range close to the phase transformation, is observed in the bcc-phases of the IVb-metal and IVb-metal alloys. Previous explanations of this behavior are briefly reviewed. Results of the temperature dependence of self-diffusion and of the isotope effect in {beta}-Zr and {beta}-Hf are presented. Remarkably curved Arrhenius plots were obtained for Zr-tracer diffusion in bcc alloys of Zr with Nb and Ti, which stabilize the {beta}-phase. Corresponding experiments in the Zr-Sc system are in progress. The results are explained assuming a monovacancy mechanism in combination with phonon assisted diffusion jumps, which become increasingly important as the temperature of the phase transformation is approached. In the bcc lattice the LA-2/3(111) phonon mode shows a considerable softening. As a consequence atomic fluctuations may be very much promoted by this mode thus reducing the effective migration energy for jumps in the <111> direction.

• OSTI ID: 5311103
• Report Number(s): CONF-840909--
• Conference Information: Journal Name: TMS (The Metallurgical Society) Paper Selection; (USA) Journal Volume: 56
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals &amp; Alloys-- Structure &amp; Phase Studies
ACTIVATION ENERGY
ALLOYS
ARRHENIUS EQUATION
BCC LATTICES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
DIFFUSION
ELEMENTS
ENERGY
EQUATIONS
HAFNIUM
METALS
NIOBIUM ALLOYS
PHASE TRANSFORMATIONS
SCANDIUM ALLOYS
SELF-DIFFUSION
TEMPERATURE DEPENDENCE
TITANIUM ALLOYS
TRANSITION ELEMENTS
ZIRCONIUM
ZIRCONIUM ALLOYS
ZIRCONIUM BASE ALLOYS