Environmental embrittlement in L1 sub 2 -ordered (Co,Fe) sub 3 V alloys

Journal Article · Wed Apr 01 04:00:00 EST 1992 · Acta Metallurgica; (United States)

OSTI ID:7116240

Nishimura, C ^[1]; Liu, C T ^[2]

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1. National Research Inst. for Metals, 2-3-12 Nakameguro, Meguro-ku, Tokyo 153 (JP)
2. Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

This paper reports that environmental effects on mechanical properties and fracture behavior of L1{sub 2}-ordered (Co, Fe){sub 3}V alloys with compositions (Co{sub 78}Fe{sub 22}){sub 3}V and (Co{sub 85}Fe{sub 15}){sub 3}V were studied by tensile test in the strain range of 3.3 {times} 10{sup {minus} 5} to 3.3 {times} 10{sup {minus} 1} s{sup {minus} 1} at ambient temperatures. The (Co, Fe){sub 3}V alloys were found to be susceptible to environmental embrittlement. The yield and flow stresses were insensitive to the test environment, while the ductility and ultimate tensile strength decreased according to the sequence of dry oxygen, vacuum, air, and distilled water. The ductility loss was closely associated with intergranular fracture, and the propensity for intergranular fracture increased in the same environmental sequence. Lower strain rate resulted in more intergranular fracture and hence lower ductility. A beneficial effect of grain refinement was observed. All these results suggest that the embrittlement was caused by moisture-induced hydrogen which diffused to grain boundaries, resulting in reduced grain-boundary cohesion and increased intergranular fracture. Grain boundaries were more intrinsically brittle in (CO{sub 85}Fe{sub 15}){sup 3}V than in (Co{sub 78}Fe{sub 22}{sub 3}V. A possible reason was suggested to explain the grain-boundary brittleness in (Co, Fe){sub 3}V alloys, based on consideration of phase stability.

• OSTI ID: 7116240
• Journal Information: Acta Metallurgica; (United States), Journal Name: Acta Metallurgica; (United States) Vol. 40:4; ISSN 0001-6160; ISSN AMETA
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
080800 -- Hydrogen-- Properties & Composition
36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
664100 -- Theory of Electronic Structure of Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALLOY SYSTEMS
ALLOYS
AMBIENT TEMPERATURE
CHEMICAL REACTIONS
COBALT ALLOYS
COBALT BASE ALLOYS
CORROSION
CRYSTAL STRUCTURE
DIFFUSION
DUCTILITY
ELEMENTS
EMBRITTLEMENT
ENVIRONMENTAL EFFECTS
FRACTURE MECHANICS
GRAIN BOUNDARIES
HYDROGEN
HYDROGEN EMBRITTLEMENT
INTERGRANULAR CORROSION
IRON ALLOYS
MECHANICAL PROPERTIES
MECHANICS
MICROSTRUCTURE
MOISTURE
NONMETALS
PHASE STABILITY
STABILITY
TENSILE PROPERTIES
TERNARY ALLOY SYSTEMS
VANADIUM ALLOYS
YIELD STRENGTH