Thermal vacancies and positron-lifetime measurements in Fe sub 76. 3 Al sub 23. 7

Journal Article · Fri Jun 15 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.11869· OSTI ID:6758101

Schaefer, H; Wuerschum, R ^[1]; Sob, M; Zak, T ^[2]; Yu, W Z ^[3]; Eckert, W ^[1]; Banhart, F ^[4]

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1. Institut fuer Theoretische und Angewandte Physik, Universitaet Stuttgart, Postfach 801140, D-7000 Stuttgart 80 (Federal Republic of Germany)
2. Institute of Metallurgy, Czechoslovak Academy of Sciences, Zizkova 22, CS-61662 Brno (Czechoslovakia)
3. Department of Physics, Qinghua University, Beijing 100084 (People's Republic of China)
4. Institut fuer Physik, Max-Planck-Institut fuer Metallforschung, D-7000 Stuttgart 80 (Federal Republic of Germany)

The formation of thermal vacancies in the intermetallic compound Fe{sub 76.3}Al{sub 23.7} was investigated between 20 and 1060 {degree}C by positron-lifetime measurements. The positron lifetime {tau}{sub {ital f}}=112 ps at 20 {degree}C indicates that no structural vacancies can be detected. The increase of the mean positron lifetime {bar {tau}} due to thermal vacancy formation starts at relatively low temperatures ({ital T}{sub 3}=475 {degree}C). The fit of a simple two-state trapping model to the temperature variation of {bar {tau}} yields an effective vacancy formation enthalpy {ital H}{sup {ital F}}=1.18{plus minus}0.04 eV, which suggests a thermal vacancy concentration at the melting temperature of several atomic percent which is much higher than in pure metals and similar to that found in some intermetallic compounds with a {ital B}2 structure. From a comparison with self-diffusion results, a vacancy migration enthalpy of {ital H}{sup {ital M}}=1.4--1.6 eV is deduced. The phase transitions in the present alloy are discussed in terms of vacancy formation and migration.

• OSTI ID: 6758101
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:17; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

656002* -- Condensed Matter Physics-- General Techniques in Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
ALUMINIUM ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DIFFUSION
ENTHALPY
HIGH TEMPERATURE
IRON ALLOYS
IRON BASE ALLOYS
MEDIUM TEMPERATURE
MELTING
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POINT DEFECTS
SELF-DIFFUSION
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
VACANCIES
VERY HIGH TEMPERATURE