Drift diffusion model of hydrogen atoms for hydrogen embrittlement in polycrystalline Ni[sub 3]Al

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(94)90144-9· OSTI ID:7277917

Han, G W; Feng, D; Ye, W J ^[1]

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1. Central Iron and Steel Research Inst., Beijing (China)

It is well known that single crystals of Ni[sub 3]Al are ductile, whereas polycrystalline Ni[sub 3]Al has very low ductility at room temperature due to the intrinsic brittleness of its grain boundaries, which results in premature intergranular fracture. Since Aoki and Izumi found that adding a small amount of boron to polycrystalline Ni[sub 3]Al could suppress intergranular fracture and improve its ambient temperature ductility dramatically, many studies have been carried out on the effects of boron on the structure and chemical composition of grain boundaries in polycrystalline Ni[sub 3]Al. At present, there have been several explanations for the beneficial effect of boron, but its origin has not yet been clearly established. Recently, environmental embrittlement of grain boundaries has been observed in polycrystalline Ni[sub 3]Al with and without boron in air involving moisture and in hydrogen gas. The initiation of intergranular crack in polycrystalline Ni[sub 3]Al relates to the local stress concentration induced by a piled up of edge super dislocation [111] <110> at grain boundary, while hydrogen atoms in the Ni[sub 3]Al superlattice would diffuse toward the end of the edge super dislocation pile-up under the action of the local stress concentration. Considering the relationships of intergranular crack initiation with both of the edge super dislocation pile-up at the grain boundary and the drift diffusion of hydrogen atoms in the superlattice toward the grain boundary, a drift diffusion model of hydrogen atoms for hydrogen embrittlement in polycrystalline Ni[sub 3]Al is proposed to explain the effects of boron content, grain size in polycrystalline Ni[sub 3]Al and test environment, tensile rate as well as test temperature on the degree of hydrogen embrittlement in polycrystalline Ni[sub 3]Al.

• OSTI ID: 7277917
• Journal Information: Scripta Metallurgica et Materialia; (United States), Journal Name: Scripta Metallurgica et Materialia; (United States) Vol. 31:5; ISSN SCRMEX; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals &amp; Alloys-- Mechanical Properties
ALLOYS
ALUMINIUM ALLOYS
BORON
BORON ADDITIONS
BORON ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
DISLOCATIONS
ELEMENTS
EMBRITTLEMENT
GRAIN SIZE
HYDROGEN EMBRITTLEMENT
INTERMETALLIC COMPOUNDS
LINE DEFECTS
MATHEMATICAL MODELS
METALLURGICAL EFFECTS
MICROSTRUCTURE
NICKEL ALLOYS
NICKEL BASE ALLOYS
POLYCRYSTALS
SEMIMETALS
SIZE