The effect of boron doping on the Hall-Petch slope of FeAl (40 at. % Al)

Journal Article · Sun Dec 01 00:00:00 EST 1991 · Scripta Metallurgica; (United States)

DOI:https://doi.org/10.1016/0956-716X(91)90152-Q· OSTI ID:5340608

Pike, L M; Liu, C T ^[1]

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1. Metals and Ceramics Div., Oak Ridge National Lab., Oak Ridge, TN (US)

This paper reports on the iron aluminide, FeAl, which has good oxidation resistance, low density, and low material cost. However, this aluminide shows limited ductility when tested in air at ambient temperatures. This embrittlement involves the reaction of the moisture in air with the aluminide and the generation of hydrogen at crack tips. By testing in dry oxygen, the environmental effect can be eliminated, but an intergranular fracture mode is still seen. This suggests that the grain boundaries of FeAl are intrinsically weak. It has been shown in both air and oxygen tests of FeAl that microapplying with boron suppresses intergranular fracture and subsequently increases ductility. For Ni{sub 3}Al, in which boron also suppresses intergranular fracture, two explanations of the beneficial effect of boron have been proposed. One claims that boron increases the cohesive strength of the grain boundaries. The other claims that boron enhances slip transfer at the grain boundaries. The primary experimental evidence for increased slip transfer was based on the observation that for powder-extruded (PE) Ni{sub 3}Al, the Hall-Petch slope, k{sub y}, was lowered by the addition of boron. The Hall-Petch equation, which relates yield stress, {sigma}{sub y} = {sigma}{sub o} + k{sub y}d{sup {minus} -.5}, where the intercept stress, {sigma}{sub o}, and the Hall-Petch slope, K{sub y}, are material constants.

• OSTI ID: 5340608
• Journal Information: Scripta Metallurgica; (United States), Vol. 25:12; ISSN 0036-9748
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM ALLOYS
BORON ADDITIONS
BORON
METALLURGICAL EFFECTS
IRON ALLOYS
CORROSION RESISTANCE
COST
DENSITY
DOPED MATERIALS
GRAIN BOUNDARIES
GRAIN SIZE
HALL EFFECT
HYDROGEN EMBRITTLEMENT
INTERMETALLIC COMPOUNDS
NICKEL BASE ALLOYS
PHASE STUDIES
REINFORCED MATERIALS
SLIP VELOCITY
YIELD STRENGTH
ALLOYS
BORON ALLOYS
CRYSTAL STRUCTURE
ELEMENTS
EMBRITTLEMENT
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
PHYSICAL PROPERTIES
SEMIMETALS
SIZE
VELOCITY
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties
360105 - Metals & Alloys- Corrosion & Erosion
400201 - Chemical & Physicochemical Properties