Nickel segregation to grain boundaries in Ni sub 3 Al alloys

Journal Article · Sun Dec 01 04:00:00 EST 1991 · Scripta Metallurgica; (United States)

OSTI ID:5334897

Subramanian, R; Robertson, I M; Birnbaum, H K ^[1]

---

1. Dept. of Materials Science and Engineering, Univ. of Illinois, Urbana, IL (US)

This paper reports that a considerable research effort has been undertaken to understand the improved ductility of hypo-stoichiometric Ni{sub 3} Al containing B relative to stoichiometric and hyper-stoichiometric alloys. A variety of techniques have shown that in ductile alloys, the level of B at the grain boundary is significantly higher than in the matrix and that the B exhibits equilibrium segregation over distances of the order of 1 nm from the boundaries. The concentration of nickel at the boundaries is less certain. Some measurements have shown somewhat enhanced Ni concentrations within 1 nm of the grain boundaries and correlations between B and Ni segregation, while in others a small amount of Ni segregation was observed but with no correlation to B segregation, and on others no Ni segregation was observed. Baker et al. report the formation of a second phase extending for distances of about 20 nm from the boundaries and having very high Ni concentrations in hypo-stoichiometric Ni{sub 3}Al containing B. These different results may reflect the different material preparation and annealing procedures that have been used. Horton and Liu have shown that the presence of the Ni-rich second phase was not necessary for the ductility of Ni{sub 3}Al. It has been suggested that a disordered fcc layer may exist at B enriched grain boundaries, and that this disorder may enhance Ni{sub 3}Al ductility by making it easier for dislocation to be transmitted through the grain boundaries.

• OSTI ID: 5334897
• 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
664400 -- Experimentally Derived Information on Atomic & Molecular Properties-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALLOYS
ALUMINIUM ALLOYS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CRYSTAL STRUCTURE
DIFFUSION
DUCTILITY
ELECTRON MICROSCOPY
ELEMENTS
GRAIN BOUNDARIES
INTERFACES
KINETICS
MECHANICAL PROPERTIES
METALS
MICROSCOPY
MICROSTRUCTURE
NICKEL
NICKEL ALLOYS
NICKEL BASE ALLOYS
ORDER-DISORDER TRANSFORMATIONS
PHASE STUDIES
PHASE TRANSFORMATIONS
REACTION KINETICS
STOICHIOMETRY
SYNTHESIS
TENSILE PROPERTIES
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY