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

Journal Article · Sat Nov 30 23:00:00 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), Journal Name: Scripta Metallurgica; (United States) Vol. 25:12; ISSN 0036-9748; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

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