Features of hydrogen-induced amorphization of the Er(Co, Mn) sub 2 pseudo-binary laves compound
- Dept. of Materials Science and Engineering, Korea Advanced Inst. of Science and Technology, Kusong-Dong 373-1, Yusung-Gu, Taejon (KR)
In this paper hydrogen-induced amorphization behavior of Er(Co{sub 1{minus}x}Mn{sub x}){sub 2} pseudo-binary Laves compound is investigated by means of X-ray diffractometry and transmission electron microscopy. The substitution of Mn for Co results in a homogeneous single phase within the whole composition range. Up to x = 0.8, C15 cubic phase is obtained, but C14 structure is found at higher Mn composition. At all compositions except for the binary ErMn{sub 2}, the amorphization phenomena are observed. Thus it is suggested that amorphization of the Laves phases by the hydrogen absorption is not concerned with the crystal structure but the chemical bonding between the unlike atoms causing the kinetic constraints of the motion of the metal atoms. By the Mn addition into ErCo{sub 2}, the amorphization temperature, which is defined as the temperature amenable to the full amorphization reaction in a fixed times of 24 h, gradually decreases from 350{degrees}C for ErCo{sub 2} to 230{degrees}C for Er(Co{sub 0.2}Mn{sub 0.8}){sub 2} within the C15 region. This behavior is explained by the variation of the formation enthalpy ({Delta}H{sub f}) and the bulk modulus of the compound with the Mn content. A compound with a high negative {Delta}H{sub f} and high modulus is amorphized at higher temperature range due to the larger activation energy barrier for the motion of the metal atoms than other compounds with relatively lower heat of mixing and modulus values.
- OSTI ID:
- 7306472
- Journal Information:
- Acta Metallurgica; (United States), Vol. 40:7; ISSN 0001-6160
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
74 ATOMIC AND MOLECULAR PHYSICS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COBALT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
ERBIUM COMPOUNDS
MANGANESE COMPOUNDS
ABSORPTION SPECTRA
ACTIVATION ENERGY
AMORPHOUS STATE
ATOM TRANSPORT
CHEMICAL BONDS
CHEMICAL REACTION KINETICS
CONSTRAINTS
CRYSTAL STRUCTURE
HYDROGEN EMBRITTLEMENT
LAVES PHASES
TEMPERATURE RANGE
YOUNG MODULUS
COHERENT SCATTERING
DIFFRACTION
ELECTRON MICROSCOPY
EMBRITTLEMENT
ENERGY
KINETICS
MECHANICAL PROPERTIES
MICROSCOPY
NEUTRAL-PARTICLE TRANSPORT
RADIATION TRANSPORT
RARE EARTH COMPOUNDS
REACTION KINETICS
SCATTERING
SPECTRA
TRANSITION ELEMENT COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360203 - Ceramics
Cermets
& Refractories- Mechanical Properties
664400 - Experimentally Derived Information on Atomic & Molecular Properties- (1992-)
400101 - Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures