The effects of segregation on grain boundary cohesive energies in Ni sub 3 minus x Al sub 1+x

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

OSTI ID:5768582

Najafabadi, R; Wang, H Y; Srolovitz, D J ^[1]; LeSar, R ^[2]

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1. Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering
2. Los Alamos National Lab., NM (United States). Theoretical Div.

The structure and properties of grain boundaries in the intermetallic alloy Ni{sub 3}Al have received considerable attention in the past several years due to their interesting mechanical properties. The aim in many of these studies was to explain the increase in ductility that occurs when polycrystalline Ni{sub 3}Al is doped with boron. Experimental observations have shown that there is a strong correlation between nickel enrichment at grain boundaries and the ductilization of boron-doped polycrystalline Ni{sub 3}Al. This grain boundary nickel enrichment has only been observed in Ni-rich Ni{sub 3{minus}x}Al{sub 1+x} (i.e., x {lt} 0). Some experimental studies have shown that grain boundary nickel enrichment also occurs in Ni-rich, boron-free polycrystalline Ni{sub 3{minus}x}Al{sub 1+x}. There have been several atomistic simulation studies that have been carried out to explore this subject. Most of these simulation studies have been done at zero temperature and without direct consideration of the important segregation effects. These studies have shown that the cohesive energy for grain boundaries rich in nickel is lower than that for the same boundaries with aluminum-rich or stoichiometric compositions. One of these same studies has shown that the grain boundary cohesive energy can be reduced even further by placing boron atoms in interstitial sites in the boundary. These results seem to give some credibility to the first model, since these changes in the cohesive energy occur for boundaries that are well ordered. One should note, however, that these simulations are carried out with stoichiometric bulk compositions, not at the nickel rich bulk compositions, where nickel enrichment of the grain boundaries and ductilization are experimentally observed.

• OSTI ID: 5768582
• Journal Information: Scripta Metallurgica; (United States), Journal Name: Scripta Metallurgica; (United States) Vol. 25:11; 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
ALLOYS
ALUMINIUM ALLOYS
ATOMS
CALCULATION METHODS
CHEMICAL COMPOSITION
CHEMISTRY
CRYSTAL STRUCTURE
DUCTILITY
ELEMENTS
ENERGY
FREE ENERGY
GRAIN BOUNDARIES
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NICKEL
NICKEL ALLOYS
NICKEL BASE ALLOYS
PHYSICAL PROPERTIES
RANDOMNESS
SEGREGATION
SIMULATION
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TENSILE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
TWINNING